Omnichrome HeCd Laser Manual

Transcription

TABLE OF CONTENTS
1.
INTRODUCTION
1.1
Laser System
1.2
Laser Safety
1.2.1 Electrical Hazard
1.2.2 Radiation Hazard
1.2.3 CDRH Labeling and Caution
1.3
Unpacking and Inspection Instructions
1.4
Operating Instructions
1.4.1 Initial Installation
1.4.2 Remote Operation Interface
1.4.3 Normal Operating Sequence
1.4.4 CDRH Remote Control Connector
1.4. 5. Remote Control Box
2
2
5
5
5
6
8
9
9
9
10
11
12
2.
THEORY OF OPERATION
2.1
Laser Head Theory
2.1.1 Plasma Tube Theory
2.1.2. Laser Head Electronics
2.2
Power Supply Theory
15
15
15
19
19
3.
GUIDE TO TROUBLE SHOOTING AND REP AIRS
3.1
Diagnostic Flow Chart
3.2
AC Power on Status
3.3
Temperature Lockout Status
3.4
Laser Head Fan Status
3.5
Power Supply Fan Status
3.6
Cadmium Reservoir Heater Status
Low
3.7
Output
3.8
Laser Output Fluctuates
3.9
Laser Beam is Distorted
27
31
32
32
32
33
34
37
38
4.
LASER HEAD TEST, ALIGNMENT, AND ADmSTMENTS
41
5.
POWER SUPPLY TEST AND ADJUSTMENT
47
6.
LASER MALFUNCTION REPORTS
57
1.0 INTRODUCTION
1.1
SYSTEM PERFORMANCE
Your Omnichrome Helium-Cadmium laser was developed for demanding
commercial, industrial, and military applications where ruggedness of
construction and reliability are essential. The laser plasma tube configuration is
similar to that of a helium-neon laser where glass/metal construction has evolved
into low cost, high volume manufacturable configurations. The laser plasma tube
is of coaxial geometry with integral hard glass-metal frit sealed resonator mirrors
utilizes cadmium of natural isotopic abundance .. High reliability and long
lifetime are obtained by optimum choice of construction materials, careful design
of the mechanical structure and of the cadmium vapor and helium pressure
control circuits, and precise control of the manufacturing process.
The Omnichrome Helium-Cadmium laser has been designed specifically for the
stringent demands of the OEMllndustrial market place. Requirements ofthe UL,
CSA, VDE and BI have been factored into the design. The laser as a component
of your system will be readily accepted by the above laboratory testing
companies. The center for Devices and Radiological Health (CDRH)
requirements have also been met.
2
SERIES J9X OUTLINE DHAWING
D
D
1. SYSTEM MOUNTING HOLES
REFERENCED WITH AN "A" ARE 1/4"
(.250) .20 UNC (ENGLISH).
2. SYSTEM MOUNTING HOLES
REFERENCED WI1H AN "8"
liRE M5 )( 0.8 (METRIC).
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f'-- ¢'-.j
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li
INDICAlES COOLING AIR FLOW
DIRECTION.
4. X INDICATES OUTER SURFACE OF
-
2.12
LASER OUTPUT WINDOW. WINDOW IS
.393 INCHES THICK.
5. INDICATED DIMENSIONS LOCATE
SERIES 56X OUTLINE DRAWING
,G8-
6 00
.
_2.-47
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4
1.2
LASER SAFETY
Please read this section of the manual carefully before installing or operating
laser.
The protective housings of the laser head and power supply are not intended to be
removed by the user. It is recommended that any maintenance or service
requiring access to the interior of the laser system be performed by an
Omnichrome representative.
Follow instructions contained in this manual for proper installation and operation
of your laser.
1.2.1
Electrical Hazard
The laser head and power supply of this laser product contain electrical
circuits operating at HIGH VOLTAGES. THESE VOLTAGES ARE
LETHAL.
If access to the interior of the laser head or power supply is necessary,
but laser operation is not necessary. TURN THE POWER SUPPLY
OFF AND DISCONNECT THE LINE POWER CORD.
If access to the interior of the laser head or power supply is necessary
while the laser is operating, EXERCISE EXTREME CAUTION TO
AVOID CONTACT WITH HIGH VOLTAGES.
1.2.2
Radiation Hazard
This laser system is designed to meet all of the requirements of
21CFRI040.1 set forth by the U.S. FDA, Center for Devices and
Radiological Health. A compliance repmi has been filed indicating the
safety features of this laser. The laser is a Class III b device which
indicates that it is capable of producing skin or eye damage if used
improperly.
5
1.2.3
Center For Devices And Radiological Health (CDRH)
The following labels were designed to warn the user of potential
LASER RAOiAnON - AVOIO DIRECT
EXPOSURE TO BEllM
INVISIBLE lASER RAlJlAnON - IIVOIO
DIRECT EXPOSURE TO BEllM
UESS THAN
5WI MW
Ht!Cd
tESS THAN
150 MVII
Hoed
ClASS'" b
lASER PRODUCT
ClASS "' b
lASER I'OOOUCT
One of these labels is located on the top rear of the Jaser head near the air outlet
fan.
~
(Dolp EX&iiB~'
One of these labels is located on the output end of the laser head below the laser
output aperture, and beam block.
-O",,.,,·1jr,,»U' ~
1Jb':t) ~ jJ.' • to ,'I~f t r
CHINO CALlh,)H~l)A lJl 'It'
III
l
'"
A
"11 til'" ·"ttl
MODEL NO. _ _ _ _ _ _ __
SERIAL NO. _ _ _ _ _ _ __
MANUFACTURED _ _ _ _ __
THIS LASER PRODUCT COMPLIES
WITH 21 CFR ,040 /IS APPliCABLE.
MAOE IN U.S.A PAT. PEND.
This label is located on the top rear of the laser head near the air exit fan.
CAUTION- Use of controls or adjustments or performance of procedures other
than those specified herein may result in hazardous radiation exposure.
6
DANGER
LAIlll UIll4T miDI I!mI
A",II IIIRECT DI'OIII. Til eUM
One of these labels is located on the base plate, near the output end of the
SAFETY RECOMMENDATIONS FOR USE OF LASER
1.
Never look directly into the laser beam.
2.
Set up controlled-access areas strictly for laser operation, and limit access to this
area to persons required to be there and who have been instructed in the safe
operation of lasers.
3.
Post warning signs in prominent locations near the laser area.
4.
Provide enclosed paths for laser beams when possible.
5,
Set up equipment so that the laser beam is NOT at eye leveL
6.
Set up a "flat black" painted target for the beam and shields to prevent strong
reflections from going beyond the area needed for the prototype development.
In addition to the above, please follow the laser safety control measure in
American National Standards Institute Z136.1-1986.
7
1.3
UNPACKING & INSPECTION INSTRUCTIONS
1.3.1
Unpacking
Omnichrome helium-cadmium laser has been carefully packaged
for shipment. If any of the packing cartons have been damaged
shipment, have the shipper's agent present for unpacking. Unpack the
units carefully and save the packaging materials for returning the units in
case of shipping damage or for service at a later date. I f one of the units
has been damaged or requires servicing for any reason, return both units.
1.3.2
Inspection
it is
Inspect your helium-cadmium laser as soon as possible
received. Look for dents, scratches or other evidence of damage. If you
observe any damage, immediately file a claim against the carrier and
notify your nearest Omnichrome representative. Omnichrome will
arrange for repair without waiting for a claim settlement.
NOTE: Prior to shipment, your helium-cadmium laser was carefully aligned and
adjusted for optimum power output and reliability. Do not open the
laser head or power supply or take any laser returned for realignment if
tampered with.
8
1.4
OPERATING INSTRUCTIONS
1.4.1
Initial Installation
After unpacking the laser head and power supply cartons, mount the
laser head and power supply in a suitable location. Any operating
orientation is allowed for Series 39X, 56X, or 112X laser heads or power
supplies.
Minor resonator alignment may be required for Series 112X laser heads
if not mounted horizontally.
NOTE: Ensure that the air inlet and outlet areas of the laser head and power
supply are not obstructed.
Connect the low and high voltage laser head cables and power cord to
the appropriate receptacles provided on the rear panel of the power
supply. Connect the other end of the low and high voltage connectors to
the receptacles at the back end of the laser head. The plugs are unique
and cannot be connected incorrectly. For the Series 112X laser heads,
there are two power supplies and two sets of HV and LV cables. Be sure
not to cross connect pairs of cables. A cable pair is comprised of a high
voltage (4 pin connector) and a low voltage (16 pin connector) cable.
Set the ON/OFF "master control" key switch on the power supply front
panel to "On" and the "Laser Control" rotary switch to "SHUTDOWN"
and then plug the power cord into an appropriate 11 OV AC wall
receptacle. Tum the laser on using the "Laser Control" rotary switch.
For Series 112X lasers, tum laser on using the two rotary switches on the
power supplies. "ON" is designated as "OPERATE".
1.4.2
Remote Operation Interface
If it is desired to use the remote control capabilities of the laser system,
the ac connector on the rear of the power supply can be connected as
described in Figure 3. For operation in this mode the rotary switch is set
to "OPERATE". This connector provides the electrical interface to a
host system and provides for switching from "SHUTDOWN"(OFF)" to
"OPERATE (ON) TO "STANDBY". In addition, it provides for an
"OVERTEMP LOCKOUT" status signal. The standby function provides
for extended lifetime of the laser when temporarily not in use. Recovery
time from standby is less than two minutes.
9
1.4.3
Normal Operating Sequence
After the rotary switch (or remote switch) is switched to the
"OPERATE" position a delay of approximately two (2) seconds occurs
for filament pre-heat before the main tube current and cadmium vapor
pressure circuits are energized. Then the main tube current circuit is
energized and laser tube (incoherent) sidelight can be seen thru the laser
head air inlet or outlet areas. The green and two yellow LED's on the
front power supply panel should be lighted indicating that the ac power,
cadmium regulator, and helium regulator circuits are "ON" .
After about two or three minutes from initial turn-on, blue laser light
should be noted from the optical output aperture of the laser head. Power
output is typically stable within five minutes after initial turn on.
i,
,
I
, I
If the red panel light is ever lighted during operation or during turn-on,
this indicates that the laser plasma tube is too hot due to blockage of the
air cooling duct (dirty air filter, etc.), or that the plasma tube is too hot to
immediately restart. In either case, leave the laser system "on" and
check for air flow blockage. Within a few minutes the laser will relight
and come back to full power operation automatically. Faster restart time
is achieved with the laser turned "on" since the internal cooling fan
reduces tube temperatures more quickly.
To shut down the laser simply turn the rotary switch to the shutdown
p"osition. Internal circuitry initiates an automatic shut down sequence
which starts immediately. First, the cadmium reservoir heater is deenergized and the discharge current is reduced to 80ma. The fans
continue to run during this phase and the green AC power indicator light
stays on. Some lasers continue to lase at lower power and some have no
emission at this point. Second, at 2 minutes 17 seconds after the key
switch is turned off the discharge current turns off. The red "Over
Temperature" indicator light turns on at this point indicatingthat the
plasma tube is too hot to restart. The [an in the laser head continues to
operate for another 35 seconds and in some situations will provide
sufficient cooling to allow the "Over Temperature" indicator light to go
out. The fan in the power supply shuts off at this time. The green AC
power indicator light is on during this phase. Third, at 2 minutes, 51
seconds the AC power is turned off completely. All indicator lights and
fans are off. To restart the laser at this point, turn the rotary switch to
operate and observe the red "Over Temperature" indicator light. If it is
off, the laser will start automatically. If it is on, leave the rotary switch
10
on to allow the fan in the laser head to cool the tube to a temperature
which is acceptable for restarting purposes. The normal internally
controlled start up sequence will only start if the red "Over Temperature"
light is off.
Note:
I
./
WARNING:
lAA
I
"
I
"I
\
I
~1
When operated on 50Hz power the time from switch off to the end of the
first phase is 2 minutes 44 seconds. The time to the end of the second
phase from switch off is 3 minutes 25 seconds.
The key switch is for emergency shutdown of the laser only. DO NOT
USE THIS SWITCH TO SHUT OFF LASER EXCEPT IN AN
_ EMERGENCY. However, for safe operation, please tum key switch to
"OFF" and remove the key after the laser has shut itself off.
CDRH Remote Control Connector
This connector provides access to the control circuit for the High
Voltage supply for emergency shut down. It should NOT be used for
every day tum off purposes. NOTE: (If external control of tum on,
stand by, and shutdown is required see Figure 2, Section lA.5 of this
manual for the schematic for the 9 Pin AC Input Connector). The
CDRH remote control function appears on Pins 13 and 14 of the 16 pin
Amp Inc. connector. It is the middle of the three connectors at the rear
of the power supply. A jumper is installed at the factory which must be
removed to gain control of the High Voltage circuits. When these pins
are disconnected there is no High Voltage to the laser tube and therefore
no lasing is possible. Ifthe two pins are reconnected after a "Safety
Shutdown" the discharge will only restart if the red "Over Temperature"
light is out. If it is on, simply allow the fan in the laser head a few
minutes to cool the plasma tube to an acceptable temperature to allow a
restart.
Please note that pins 13 & 14 control the main Solid State Relay in the
Power Supply and carry < 25 rnA. However, these circuits are common
with AC line and require isolation from chassis or any ground. An
insulated switch or relay should be used to open or close these circuits.
Due caution should be exercised to avoid any bodily contact with these
circuits due to the possible shock hazard while the supply is energized.
11
-
. -~
1.4.5
Remote Control Box Via 9 Pin Connector
THE ROTARY SWITCH ON
POWER SUPPLY MUST
IN
THE "OPERATE" POSITION FOR REMOTE CONTROL
LASER. Any of several configurations of remote control are available
ACIREMOTE connector on the rear of
Model 100
using the 9
power supply. If the remote control will be located less than 15 feet
from the power supply, a simple remote rotary switch is possible as
shown in Fi gure 2A. If the remote control will be more than 15 feet, it is
recommended that switching be located near the power supply to reduce
EMI pickUp in the switch lines.
Pins 1 & 5 must be shorted to "OPERATE" the laser. Opening pins 1 &
5 will cause laser to "SHUTDOWN".
If pins 2 & 6 are shorted at the same time pins 1 & 5 are opened, the
laser will go into the "STANDBY" mode.
Remote control may be effected by connecting two mechanical relays
with normally open contacts, with one relay for each circuit (1-5 and 26).
Mechanical relays are available in
type packaging that will operate
from
logic levels. One type is Magnecraft PfN WI71 DIP-7.
The pin 1-5 circuit may be controlled with a solid state relay containing
an
and a light sensitive
This
require less than
100mA, AC. The triac should have at least a 200V rating (for 120V
line).
Both of the above circuits are at LINE POTENTIAL. They must be
isolated from ground and each other, or any other circuits.
Note:
If the Remote Control Cable is greater than 2 meters in length, install an
emission indicator light in the remote control box.
12
Customer
FIGURE 2A.
Supplied
Remote
For
123
Operat ion
~REHOVE FOR REMOTE OPERATION
'Qo
.. 6-~r=t:
I
I
2P 3T Switch
EXTERNAL
TEMP
FACTORY INS1ALLED JUMPER
° ~ a--==t
o~o
I-SHU1DOWN
2-0PERATE
3-STANOBY
I
I
I
I
I
I
~~~KOUT ~~~~~~_______
._________
OIALIGHT 521-9240 OR EDUIV.
('
.. Of--.- - - - - - - - ~----------------------
17 VAC NEUTRAL
CHASSIS GROUND
117 VAC HOT
!
In
~ y. .rot-------I· ;>-----------330
I
I
lAC LINE
ICORD
I
OHM
5
8
<;I
7
3
-'1
NOTE: FOR RADIATION SAFETY CONTROL PER BRH REGULATIONS SEE SECTION 4.4
FIGURE 2B.
REHOTE
CONTROL
OVER
ft
FROM LASER.
15
~f------------- 5
1
i-SHU1DOWN
2-0PERATE
3-STANDBY
2
3
°fo
L-Qf-------------
-------115
~'i)~--------- 6
VAC
}----------- 2
HO
AC LINE
N
FIGURE 2C.
FOR OPERATION OF
LASER FROM TTL
LEVELS.
0
ENERG I ZE 'S' .
SHU1DOWN: OPEN'S'.
STBY: OPEN B, ENERG I ZE C.
'A' IS COHMON.
~!.14
OPERA TE:
2
r---~~ HAGNECRAFl
W171DIP-7
C cr----------------------~
8
~~7-.-B-------------------
...
2
6
~L14
L-or-7_,_8_ _ ___
.------......
5
MAGNECRAFT
W171DIP-7
A
NOTE:
AMP PIN
606181-1 FEMALE SOCKETS USED IN 9-PIN PLUG.
13
14
SECTION 2.0
THEORY OF OPERATION
2.1
LASER HEAD THEORY
Omnichrome helium-cadmium lasers corne in four frame sizes: 39cm, 56cm,
74cm, and 112cm. All Omnichrome helium-cadmium laser heads are made up of
a plasma tube, resonator structure, head electronic printed wiring board, housing
and cable assembly. All models of plasma tubes are similar in both design and
theory of operation and all head electronics are identical excepting a few
component differences. The primary differences between various models of laser
heads are in the resonator structures and housings.
2.1.1
Plasma Tube Theory
A typical Omnichrome He-Cd laser is shown pictorially in Figure 3. The
main features of the plasma tube are identified in this picture.
Omnichrome helium-cadmium lasers are positive column metal vapor
discharge lasers using cadmium of natural isotopic abundance as the
optical gain medium and helium as the start gas and cadmium excitation
medium. Cadmium is stored in a reservoir near the anode end of the
plasma tube and heated by a combination of internal and external means
to be a temperature near 250 C producing a few milliTorr of cadmium
vapor pressure in the reservoir. The helium pressure in the plasma tube
is a few Torr. Cadmium vapor is ionized in the discharge capillary and
transferred
the reservoir to the cathode end of the capillary by
cataphoresis at the rate about 1 milligram per hour. Within the capillary
Penning ionization of the cadmium atoms by metastable helium atoms
produce the necessary population inversion to produce optical gain at
441.6 nrn or 325.0 nm.
The output power and optical noise of the He-Cd lasers is strongly
affected by plasma tube current, helium pressure and cadmium pressure.
Regulation circuits are provided in the power supply to ensure that an
three parameters remain constant during the lifetime of the laser.
Plasma tube ignition is provided by a voltage multiplier module within
the power supply. The main discharge circuit is a switching
15
ANODE MIRROR FLANGE(HIGH VOLTAGE)
DANGER
CA TAPHORET I C CONF I
CAPILLARY
""-"LA""'L'
1'-------
CADMIUM RESERVOIR
AND EXTERNAL HEATER
MAIN DISCHARGE CAPILLARY
PLASMA TUBE TEMPERATURE
SENSE DIODE
CATHODE(NORMAL + SPAHE)
~
HELIUM PRESSURE REGULATOR
_ _ _ _ _ WITH HIGH PRESSURE RESERVOIR
CADMIUM CONDENSER SECTION AND
REMELT HEATER
---------CATHODE CONNECTIONS(NORMAL + SPARE)
~iII!S~ _ _ _-CATHODE
FIGURE 5.
MIRROR FLANGE (OUTPUT END OF TUBE)
PLASMA TUBE SCHEMATIC
16
inventer type providing a regulated tube current of 100 mAo Switching
frequency is 20KHz.
Helium pressure within the plasma tube is regulated using a closed-loop
control system which maintains helium pressure within 1% of
set
values. Heat loss type sensors within the plasma tube are used to sense
both helium pressure changes and ambient temperature changes. These
sensory signals are then used to control the rate of flux of helium from a
side arm reservoir into the plasma tube. The time constant for this
circuit is of the order of one hour. Helium demand by the plasma tube is
indicated by the yellow "HE HTR" light on the front panel of the power
supply. HELIUM PRESSURE SHOULD NEVER BE ADJUSTED
USING THE POTENTIOMETER IN THE LASER HEAD.
Plasma tube voltage is a sensitive measure of the cadmium vapor
pressure within the discharge capillary of the plasma tube. Plasma tube
voltage is used in a closed loop feedback control system to regulate the
amount of heat provided to heater bands around the cadmium reservoir
near the anode of the plasma tube.
Power to the heater is commutated at the line frequency using a triac
control. The duty cycle of the cadmium heater is a maximum of about
-M% during laser tum-on, and about 40% during normal operation at
;, normal ambient temperature conditions (75°F). Adjustment of cadmium
pressure is performed using potentiometer in laser head. High tube
voltage corresponds to low cadmium pressure, low tube voltage
corresponds to high cadmium pressure. Time constant for this control is
about 30 seconds.
The normal operating sequence for the plasma tube is described with
reference to Fig. 3. When the power supply is switched on, power is
immediately supplied to the normal tube cathode (6.2VDC AT 1.8A) for
about 2 seconds. If the plasma tube is at or near room temperature as
sensed with the tube temperature sense diode (>.5V Across diode), the
main tube current circuit is energized providing up to 27KVDC to the
anode of the plasma tube. Ignition occurs immediately and a stable
discharge of 100mA is maintained from the anode through the
cataphoretic confinement and main discharge capillaries to the
normalcathode. If the plasma tube is off but remains too hot (.5V across
diode) due to recent operation of the plasma tube, the main discharge
circuit will be inhibited until the plasma tube temperature decreases to a
suitable value. If the plasma tube is operating and the temperature sense
17
diode voltage drop decreases below 0.2SV due to excessive ambient
temperature, air flow blockage, or fan failure, the main discharge circuit
will shut down.
all these cases where the tube
sense
diode indicates overternperature conditions for the plasma tube the
"OVERTEMP LOCKOUT" LED on the power supply will be lighted.
The tube anode voltage after ignition is typically about 1300 volts for
Series 39X and 2000 volts for Series 56X plasma tubes.
As soon as the 100mA discharge is established, power is supplied to the
cadmium reservoir heater (SVAC at 3A). The power to this heater is
controlled by a triac commutating circuit which regulates plasma tube
voltage. During initial warmup
circuit operates at the maximum
duty cycle about 80%.
As the temperature of the cadmium reservoir begins to increase, the
cadmium vapor pressures increases and is drawn into and down the main
discharge capillary toward the cadmium condenser section of the plasma
tube.
After about two minutes from startup the cadmium vapor pressure
increases enough to cause the plasma tube anode voltage to begin to
drop. Since anode voltage is a very sensitive measure of cadmium vapor
pressure in the capillary, it is used in the cadmium reservoir heater
regulation circuit to regulate cadmium vapor prcssurc. Within about five
minutes from startup the anode voltage stabilizes to its normal operating
56
value which is about 9S0V for Series 39 and 1650V for
tubes. After stabilization of the tube voltage the duty cycle of the
cadmium reservoir heater is in the 3 S to 40% range if the
IS
adequate.
Tube voltage regulation accuracy is usually within +2 or 3 volts. NOTE:
If AlC power to the laser is interrupted for more than about 40ms the
plasma tube will extinguish. Ifthis occurs while the tube is hot, the tube
will not immediately reignite. The tube temperaturesense diode inhibits
plasma tube ignition until the diode voltage drop increases above about
SOO mY.
The helium pressure regulator assembly is a side appendage to the
plasma tube. It contains thermistors used to directly measure the local
helium pressure, a high pressure helium reservoir, a temperature
dependant permeable membrane separating thecma tube from the
helium reservoir, and a heater to cause transfer of helium from the
18
reservoir into the plasma tube. The helium pressure regulator and its
control circuit operates totally independently from the remainder of the
plasma tube.
time constant for helium regulation are hours so that
nothing rapid is occurring with this device. CAUTION it is important
not to adjust the potentiometer
8 the laser head since
can cause
the plasma tube helium pressure to increase with a few hours. But the
pressure cannot be caused to decrease in so short a time.
2.1.2
Laser Head
Electronic~
Series 39X and 56X laser heads have a single printed wiring board and
iltcd wiring
harness assembly. Series 112X laser heads have two
boards and two harness assemblies since they are made up of two Series
56X plasma tubes.
The only component variation between laser head printed wiring boards
and cable assemblies is R19 on WB3. R19 is 21K for Series 39, 13,.3K
for Series 56X and 12.lK for Series 112. This resistor sets the plasma
tube anode voltage adjustment range of the potentiometer R2.
On the rear panel of each Series of laser heads is a set of test points
which allow the easy measurement of several key operating functions of
the laser head. The blue test point is chassis ground. The black test
point is circuit ground. Between these two test points can be measured
the tube current, It, where 100mA of tuhe current equals a 100mV
measurement. Between the black and red test point can be measured the
plasma
voltage, Vt. And
black and yellow test
can be measured the helium pressure regulator reference voltage, Vr.
Using the tube anode voltage and adjustment potentiometer, R2, a wide
range of laser head performance conditions can be adjusted. Be sure not
to adjust the helium pressure regulation potentiometer, RIg, by accident.
Maximum laser output is achieved at about 950V on Series 39 and
1650V on Series 56 and Series 112 laser heads. Variations in the optical
noise amplitude and spectrum can be obtained by adjustments on anode
voltage using R2.
2.2
POWER SUPPLY THEORY
In the Omnichrome He-Cd laser power supply, there are three separate control
loops: Tube current, Cd pressure, and He pressure.
19
2.2.1
Tube Current Loop
Tube CUlTent loop utilizes a Pulse Width
an S02524J as
the main element in the loop. This I.C. produces a variable pulse width
signal to control the Switching transistor, Q2.
Isolation of Q2 Base signal is necessary due to the different potentials
present. This is effected by the use of a fast optocoupler, a 6N 136, Q24,
which contains a LED, a photo diode, and a transistor. The signal out of
Q24 feeds an emitter-follower, Q23 and a pull-up resistor, Rl16, to
supply sufficient drive to saturate Q22.
Now, Q2, the Switching Transistor, has its Emitter returned to the
common of a +/- 9V Supply formed by CR40, C3, &1 C4. When Q 22 is
OFF the Base ofQ2 is pulled up toward +9V by RI13, 82 Ohms. When
Q22 is ON, the Base ofQ2 is pulled down toward -9V thru Rl14, 12
Ohms.
A divider is formed by Rl13, & Rl14 so that 02 Base does not reach its
Zener voltage value. By driving 02 Base negative, a faster, more
complete turn-off is realized.
The main H. V. Bridge, CRl, feeds two 1400 ufcapacitors, CIa & Clb,
and is current limited by a 1 Ohm resistor, R 1. The positive side of the
capacitors go directly to the center tap of the H. V. Transformerprimary,
T3, and the cathode of CR9. The negative side feeds the Emitter of 02,
with its Collector connected to the Anode ofCR9, a lN3893R, and one
end of the Inductor, Ll. When Q2 is ON, it 'charges' L 1. When Q2 is
OFF CR9 conducts, protecting 02 and completing L 1
Since
there is no significant filter capacitor after Ll, it operates as a current
source for the Inverter transistors, 03 & Q4, and is connected to Q3,4
Emitters, and returns to the circuit Common of US.
The Inverter transistors are driven by the S02524 I.C. thru Q8, which
drives U4, a Flip-Flop 1. e. (7474). This, then, delivers two 50<Yo
squarewave signals, 180 degrees out of phase, to the SG3627 I.e. which
supplies these signals, with current-limiting, to the transistor Bases. The
7474 and 3627 both use +SV supplied by U3, a 5 volt regulator I.C. The
3627 I.e. has two 2.7 Ohm resistors to limit the drive current to the
Inverters. R2S, 34 & C14, 17 cause the Bases of Q3,4 to go negative
during turn-off, insuring a fast, clean turn-off.
20
The Switcher, Q2, operates at 40 KHZ. The Inverters, Q3, & Q4 operate
may be
at 20 KHZ. The frequency is determined by C 11 and RIll,
checked
POWER SUPPLY CHECKOUT
T3 is a step-up transformer to develop the H.V. required by the Plasma
Tube. T3 feeds the H.V. Module which contains a diode bridge, a i1lter
capacitor, and a Start-Voltage multiplier to develop the very gh
voltage required to start the Plasma Tube.
When Tube is lit, current flows thru the tube and to the chassis thru the
filament circuit. From the chassis the current flows up thru R48. 10
Ohms, then thru the overcurrent circuit and back to the I-LV. Module, pin
5.
The I.e., ARl, contains four Op-Amps, one of which acts as the Tube
Current sense. U7 has a regulated +5V output at pin 16, which feeds a
divider, R39 & I R40, modified by R82. A reference voltage is derived,
l+I-.(nV, to feed ARl, pin 2. Pin 3' sees' the voltage drop across R48.
Thus, 1 if pin 3 is less than pin 2, the output at pin 1 goes low, near OV,
and supplies no current to Q9 thm R52, 1 390 Ohms. This allows U5, 1
SG2524, to tum ON the Switcher, Q2, tomaximum duty-cycle for
maximum current to the Inverters. This supplies full current to the
Plasma Tube.
If pin 3 of ARl is more positive than pin 2, then pin 1 will go high,
causing maximum drive to Q9, reducing the Switcher duty-cycle to
mll1l1TIum.
the voltage
across
is
I I
the
circuit will balance and maintain this condition. (100 mA) This, then,
describes the Tube Current Control Loop.
2.2.2.
Cd Pressure Control Loop (Tube Voltage)
Now, with a stable Tube current flowing, the Tube voltage, may be used
to indicate the relative Cd pressure. More Cd means a lower Tube
voltage and less Cd means a higher Tube voltage.
At pin 1&7 of the H.V. Module appears the tube voltage, measured just
before the Start Multiplier. This start Multiplier has a constant 10 to
15V drop and for practical reasons can be ignored. Pins 7&1 are
connected to a 10 Meg, H.V. resistor and thru R19 to Circuit Ground.
The voltage across R19 represents a fraction of the Tube voltage. It is
applied to the second section of ARl, 1 pin 10, acting as a voltage
follower to avoid loading of R19 signal.
21
In the laser head on WB3, is another +5V regulator, Ul, supplying a
. constant 5V reference to a divider formed by Rl, 2, & 3. R2 allows
adjustment ofthe voltage applied to pin 12 of ARl on WBl, which
results in setting the Tube voltage to an optimum value. (Actually sets
Cd Pressure).
C23, R53, C26, R57, & C27, act as a lead-lag network to compensate for
the Thermal Lag in the Tube and Cd Htr assembly. U7, another SG2524
is again used as a Pulse Width Modulator. but this time at 120 HZ.
The AC applied to CR19 is sampled by two diodes. CR20 and CR21.
They deliver a full-wave signal to Q 12 which tums-ofT only at the crossover points of the wavefonTI. R45 and C44 help remove any RF that
migbt affect circuit operation. R4! insures tbat the transistor Base will
reach ground potential at tbe cross-over points. R44 cbarges e21 when
Q 12 is OFF. CR24 allows a full cbarge of C2l. CIU5 supplies a
negative pulse to pin 3 of U7 each time Q12 conducts. Tbis serves to
synchronize the 2524 to tbe line frequency.
If tbe signal at pin 10, ARI (Tube voltage) is higber tban tbe Ref signal
from WB3, R2, then pin 14 of ARI will go low and increase tbe Cd Htr
duty-cycle. This will cause the Tube voltage to begin to drop. When the
Tube voltage, at pin 10 equals the Ref voltage at pin 12 then the circuit
will balance and maintain a constant Tube voltage (Constant CSD
Pressure). It should be noted that the thermal response is slow and 2 to 3
minutes will be required for a stable Tube voltage, after IU is adjusted.
The triac on WB2 is the actual controller of the Cd HiI' current. Each
time the AC waveform feeding the triac crosses zero, the triac turns
OFF. How soon it is triggered ON during each half-cycle is dependent
on U7 and the difference between Tube V arid the Cd refV. A resistor
divider of R51 & R54 clamp pin 9 of U7 thru CR26, limiting the
maximum Cd Htr duty-cycle to approx. 80%. This is necessary to insure
reliable triac triggering.
C31 is charged by R67 during the off-time of Q15, with CR28 providing
a full charge each time. When Q15 conducts, C31 delivers a negative
pulse to the triac, Q 1 on WB2 thru CR29 & CR30. These diodes reduce
the peak amplitude and tend to reduce RF contribution to the triggering
of the triac. At turn-on of the system, the Tube voltage is always high,
since no Cd is present. This turns ON the Cd Htr to maximum (~80%)
and continues until the Tube voltage drops to the set value.
22
2.2.3.
He Pressure Control Loop
Inside the Plasma Tube are mounted four thermistors. Two for control
and two for spares. One thermistor is used mainly to sense
and the other to sense temperature. These thermistors are nominally
5000 Ohms at 25 degrees C. In the circuit, one thermistor is operated at
approx. 30 mA, causing it to heat up considerably, lowering its
resistance, since it has a negative temperature characteristic.
The other is operated at about 3mA, with very little heating effect. Both
thermistors sense temperature, but the 30mA unit also senses He density
by heat-loss. The thermistors are connected in a bridge configuration,
with a voltage comparator, an LM311, with one input looking directly at
the 30mA thermistor thm R8. The other input 'sees' the 3mA thermistor
ihm RIO and a network formed by R6, R7 & R9 (to compensate for
difference in thermistor voltages).
In effect, bolh thermistors respond to temperature, but one responds to
He pressure, as well. In this manner we can control He pressure over a
useable range of temperatures.
To balance the thermistors at a given He pressure, the voltage applied to
the thermistors from U2 on WB , can be varied by R 18 over a range of
S.OV to lO.2V. Since the 3mA thermistor is not materially heated, it
responds in a positive manner to the applied voltage. The 30mA
thermistor, however, follows immediately in a positive manner, but then
in a negative manner as the thermistor
up (negative
characteristic). This takes a minute or two to stabilize. By carefully
setting RlS, a good balance can be obtained at a given He pressure. The
output of the 311, ARl, WB3, 1 drives Q 1 & Q2 which drive the
Htr
triac, Q2, on WB2.
2.2.4.
Line Fault Relay
In the event of a brief Line Power loss, the danger of Power Supply
failure is great. The line Fault Relay helps to prevent this failure mode.
Without the Line Fault circuit, suppose a line drop-out of a few seconds
occurred. The Tube goes out in about 60mSec, leaving approximately
80 Volts on the main capacitors. The low voltages will go to zero.
When the power returns, the low voltage will stmi to rise, taking about a
100 mSec or more to reach the safe operating range. This means that we
are powering up the main circuit with 80V still on the Switcher and
23
Inverter transistors. Q2, 3, & 4 are not being fully turned-on during this
period, and the safe operating area of the devices are being exceeded!
Now, with the Line
relay circuit in place,
relay will drop out
SSR and puls a 10 Ohm
after about 40 mSec. This disconnects the
resistor across the main capacitors. Also, the filament delaycap, C9 is
discharged. CIon the Line Fault board is discharged. When the line
voltage returns, a delay of about 112 to 1 Sec before the Line Fault relay
pulls in. This allows the main caps to completely discharge before
allowing supply to come ON. After the delay, the relay pulls in enabling
the H.V. SSR and the filament delay, of 2 to 4 Seconds. The H.V. SSR
cannot be energized till after the filament delay. This insures that the
low voltages will be up and the transistor drive is at full power. U4
holds off Q27 during filament delay, thus inhibiting K2, FI.V. SSR.
Failure of the Power Supply due to Line dropout is virtually eliminated.
2.2.5.
Shutdown Timer
The Plasma Tube has internal mirrors that would be damaged if Cd is
allowed to collect on them. In the Anode end of the Tube is the usual
confinement section to prevent the flow of Cd toward the Anode mirror.
However, this is only true while the Tube is ON. If the power is cut-off,
(plug-pull) then a small quantity may get on the mirror. Repeated 'hot'
shutdowns of this kind can seriously shorten the useful life of the Tube.
A timer I.C., CD4060BE, is employed to avoid the problem. Plugging in
ON the toggle
the line cord energizes the Line Fault relay,
switch applies AC to WB 1, 1 4. This charges up C35 to approximately
to
applied to pin 16
22V. VR2 regulates at lOY. CR37 allows
ofU2, Q3, 21, 28, 29, pin 12 reset), and Q4 thru RI08 allowing enabling
of Cd control circuitry. In the reset mode, U2, pins 1&3 are 'low',
turning OFF Q3&I28. This lets Q21 &129 to turn ON and energize K2,
the low voltage SSR. Power is also applied to Q25 collector. Q25 is
dependent on Q26, 27, & U4 before any drive can be supplied to K2,
tLV.SSR. Q25 will be turned ON when the filament delay is finished.
The Laser is operating and the toggle switch is turned OFF. C35
discharges, CR37 decouples, reset is removed and the Timer starts
counting Line pulses (60 HZ). Q4 turns OFF, removing power from Cd
controller circuit and the Tube current is reduced to ~82 rnA.
The Timer will run for 2'16" before pin 1, U2 will go 'high', turning ON
Q3, turning OFF Q21 and removing power from Q25. This turnsOFF
24
K2, H.V.SSR and the Tube goes out. Timer continues to count to 2'51"
when pin 3 goes 'high' where Q28 goes ON and Q29 goes OFF,
removing drive from K2, L.V.SSR. At this point, all power is
, and
the
system is shut down.
The above sequence allows the
to be cut-off, the Tube current
reduced to 82mA, and time for the Cd to leave the Tube bore prior to the
Tube cut-ofT. This reduces the chance of any CD getting on the mirrors.
2.2.6.
Cd Inhibit Circuit
Q14 senses the presence of Tube current in ordcr to enable to Cd
controller, U7. This prevents Cd build-up in the Tube in case it docs not
lite. The Cd htr is also inhibited during the shutdown sequence.
2.2.7.
Temperature Lockout Circuit
A diode, CR2, is mounted directly on the Tube body to sense
temperature. The voltage drop of this diode is about .6V at 25 C, and
drops with an increased temperature. The diode is fed with
approximately 1 mA from U7, pin 16 (+5V Ref) ihru R72. This voltage
is sensed at ARl, pin 5. A voltage divider, R70, R76, applies W.53V to
ARI, pin 6. As long as the diode voltage is below .53V, the output of
ARI, pin 7 will go 'low', ~~O V, cause Q17 and Ql1 to turn ON. Q17
sends an overtemp signal to 13, pin 3, and Qll resets Q4, removing
drive from Q27 and turning OFF K2, H.V.SSR. This condition
is cool enough
a safe restart.
When the Tube lites, Q16 senses the Tube current and parallels R76 with
R73, changing the Temp Ref to .25V. This allows the Tube to run hotter
than it can safely start. Say the Tube is operating, the temp diode is at
.3 8V, and there is a brief power interrupt. The Tube goes out. Q 16
turns OFF, raising the Ref to .53V again. Now the povver resumes, hut
an oveliemp condition will exist because the diode voltage is less than
.53V. When the Tube has cooled to a safe temperature, it will
automatically start.
If the fan were to fail or the air circulation in the head were blocked the
diode would heat up until the diode voltage goes below .25V. This will
again trigger the overtemp condition In this manner, the Tube is not
allowed to start hot nor allowed to overheat to a dangerous level.
25
2.2.8.
Overcurrent Lockout
The return from the
Module, pin 5, goes thru
and R12,
1.
The R8, R9 combination allow approximately 114 mA to flow before
turning ON Q4 an Q7, triggering the regenerative switch, Q5 and Q6
which locks-up, resetting U4, WBl, again turning II.V. and the Tube
OFF. The circuit will remain in the Locked-up mode until the AC cord
is removed for about 3 Sec, after which the circuit resets automatically.
lfthe overcurrent still exists, then it will lock-up again.
2.2.9.
Filament Voltage Regulator
Ulan
is the filament regulator. The filament voltage, at \VB 1,
19, may be set with R2 on WB 1. The nominal setting is 5.55V. It is
measured against Chassis ground. This insures Low-Noise operation
over the full line-voltage range.
2.2.10.
StandbyMode
Standby is initiated by opening the jumper from J3, 1 to 5, and
connecting D, 2 to 6. Opening 1-5 turns the Cd Htr off and reduces the
Tube current to 82 rnA. This also starts the Shutdown Timer. However,
connecting 13, 2 to 6, inhibits the Timer and allows the Laser to run in
Standby for an extended pcriod oftimc. This can extend the lifetime or
the Tube by not using Cadmium during Standby. The Timer counts the
line frequency and this signal appears across RI07, a 16V half-wave
pulse. Shorting 13, 2 to 6, shorts Rl 07, thus the Timer does not count.
In the newer model of Power Supplies, a rotary switch replaces the
toggle switch with, SHUTDOWN, OPERATE, and STANDBY
positions. Of course, you may still operate the Laser System remotely
by extending Pins 1 & 5 and 2 & 6, of D. lfthe remote operation is
used, then the Toggle (or the rotary) switch is put in the RUN or
OPERATE position, and control is by the remote 'box'.
26
SECTION 3.0
GUIDE TO TROUBLE SHOOTING AND
FOR
OMNICHROME
As shipped from the factory, your Omnichrome helium-cadmium laser should provide
peak performance with no adjuslment or alignment. Should there occur any problem
during the life orihe laser system, the following guide should be of help in identifying
the problem and its solution.
Before beginning a potentially lengthy trouble shooting procedure:
I.
Is there A.C. to
2.
Is there any blockage or restriction of cooling air flow to the laser head or power
supply?
3.
Is the red power supply overtelTlperature lockout status light "on"?
4.
Is there anything blocking the laser beam?
5.
Did you wait 5-10 minutes from initial turn-on?
6.
Is the laser status light on in the head?
7.
Are the cables firmly mated at the rear of the power supply?
8.
Is the red overcurrent status light "on"?
9.
Is emergency keyswitch "on" (horizontal position)? lfnot, turn keyswitch "on".
laser system?
Three categories of trouble shooting are described below:
1.
Laser system will not start, no laser output or system shuts off.
2.
Low laser output power.
3.
Laser output power fluctuates.
Note: THE KEY SWITCH ON THE FRONT PANEL OF THE POWER SUPPLY IS
NOT TO BE USED FOR NORMAL SHUTDOWN OF THE LASER. THIS KEY
SWITCH IS FOR EMERGENCY TURN-OFF ONLY. USE THE ROTARY SWITCH
FOR NORMAL OPERATION OF THE LASER.
27
SUMMARY OF HE-CD LASER
MALFUNCTION INDICATORS
INDICATOR
NORMAL CONDlTION
POWER SUPPLY INDICATORS
GREEN "POWER ON" STATUS LIGHT (FRONT PANEL)
-"ON" INDICATES AC POWER TO POWER SUPPL Y.
-"OFF" INDICATES NOT AC POWER TO POWER SUPPLY.
- CHECK AC LINE OR MAIN PIS FUSE.
ON
ON
YELLOW "Cd HEATER" STATUS LIGHT (FRONT PANEL)
- "ON" INDICATES CD HEATER ON AND DISCHARGE ON.
- "OFF" INDICATES NO DISCHARGE OR CD HEATER CIRCUIT
MALFUNCTION (SEE SECTION 2.2.2).
YELLOW "He HEATER" STATUS LIGHT (FRONT PANEL)
- "ON" INDICATES TUBE ASKING FOR HELIUM.
- NORMALLY "ON" FOR 1ST 5 TO 15 MINUTES OF OPERATION.
- NORMALLY "OFF" DURING LONG TERM OPERATION.
- IF "ON" FOR MANY HOURS SEE SECTION 2.2.3.
ON OR OFF
RED "TEMP LOCKOUT" STATUS LIGHT (FRONT PANEL)
- "ON" INDICATES PLASMA TUBE IS TOO HOT TO START.
- IF "ON" LEAVE LASER OPERATING. IT WILL COOL DOWN AND
RESTART.
- TYPICALL Y CAUSED BY AC LINE INTERRUPTION OR NO COOLING.
- SEE SECTION 2.2.7
OFF
RED "OVERCURRENT LOCKOUT" STATUS LIGHT (CAN BE SEEN
INSIDE PIS THRU AIR INLET LOUVRES).
- "ON" INDICATES TUBE CURRENT TOO HIGH. IF "ON", UNPLUG AC
LINE TO PIS, WAIT 3 SEC AND RESTART.
- SEE SECTION 2.2.8
OFF
POWER SUPPLY COOLING FAN (REAR PANEL)
- "OFF" INDICATES OVERTEMP LOCKOUT CONDlTION OR HIGH
VOLTAGE CIRCUIT FAILURE IN PIS.
- SEE SECTION 2.2.1.
ON
LASER HEAD INDICATORS
RED INDICATOR LIGHT (FRONT PANEL)
- "ON" INDICATES AIC POWER TO LASER IIEAD
ON
LASER PLASMA TUBE DISCHARGE (INSIDE HEAD)
- "ON" INDICATES ll1GlI VOLTAGE CIRCUIT FUNCTIONS
-IF "OFF", ClIECK IF "OVERTEMP LOCKOUT" STATUS LIGHT IS "ON",
OR HIGH VOLTAGE CIRCUIT HAS MALFUNCTIONED
- SEE SECTION 2.2.1.
ON
LASER HEAD FAN
- "ON" INDICATES LOW VOLTAGE CIRCUIT ENERGIZED.
-IF "OFF", PIS LOW VOLTAGE SECTION MALFUNCTION.
ON
28
LASER HEAD TEST POINT MEASUREMENTS
USE A HIGH Il'viPEDANCE, NON GROUNDED, DIGITAL VOLTMETER
TEST POINTS
------------------------------------------------------ -~----------------------------------------------
BLACK TO BLUE
1.O±.05
- MEASUIU~S PLASMA TUBE DISCHARGE CURRENT (1 VDC=l OOmA)
- SHOULD BE STEADY WITHIN 10mV.
BLACK TO RED
-FOR 39X, 1.2±.1 VDC
-FOR 56X, 1.8±. J VDC
-FOR 74X, 2.6±.lVDC
-FOR 112X,1.8±.lVDC
lOOnV)
- MEASUIUiS PLASMA TUBE VOLTAGE (1
- VOLTAGE SHOULD BE STEADY WITHIN lOmV,MAX.
- IF LARGE VARIATIONS (>30mV) OCCUR WITH PERJOD
IN RANGE OF 30 SECONDS, CHANGE TUBE VOLTAGE UPWARD
USING "Vt ADJ" POT ON LOWER REAR OF LASER HEAD.
BLACK TO YELLOW
9.S±.7VDC
- MEASURES HELIUM PRESSURE REGULATION SET POINT.
- SHOULD BE STEADY WITHIN LESS THAN lOmV.
- THIS VOLTAGE IS FACTORY ADJUSTED ONLY USING THE
"VR ADJ" POTENTIOMETER ON LOWER REAR OF LASER HEAD.
29
CAUTION
DO NOT ATTEMPT TO MAKE ANY ELECTRONIC MEASUREMENTS WITHOUT
READING THE FOLLOWING:
1.
There are potentially lethal voltages inside the power supply
Exercise extreme caution if covers are removed.
laser head.
2.
' Before starting laser to perform fault diagnosis - install a line isolation
transformer since circuits are at line potential. Component failures can otherwise
occur during probe testing.
3.
If an oscilloscope is to be used - isolate the oscilloscope from the line and ensure
that personnel do not touch scope cabinet during test.
4.
The highest voltages accessible inside the Power Supply arc at the terminals of
the two parallel 10K ceramic resistors located in front orthe exhaust f~m.
5.
Only a limited number oftest points can be probed during operating ofthe PIS
without damaging components. Low Voltage circuits should be tested only aiter
removing push-on terminals to "high voltage" bridge rectifier adjacent to large
filter capacitor. Be certain that those push-on terminals don't touch the chassis or
any other paxis during testing since 115 V power is present.
REFER TO DIAGNOSTIC FLOW CHART
LASER WILL NOT
NO LASER OUTPUT
LASER SHUTS OFF
3.1
When the laser system is turned "on", did the laser plasma tuhe discharge light?
i.e. [s there a neon-sign-type sidelight emanating from the side of the glass laser
tube when viewed from the laser head air inlet or exhaust apertures.
3.1.1.
If tube discharge is "off" 1, go to Paragraph 2.0
3.1.2
If tube discharge is "on", 1 go to Paragraph 6.0
30
UNIT WILL NOT START
NO LASER OUTPUT
LASER SHUTS OFF
lAM)
TU& OISOIAFGE IS
I
I IIC
OFF
OFF
00
I
I
1. QiEO( PIC PWR TO PWR SUPPLY
:2. QiEO( IoIAIN PWR SUPF'L Y FUSE
UK niX CM-I I D1fOJ1E
FOR INSTRUCTIONS.
OFF
I
OVERCURRENT Loc::KOUT
LIGHT IS
I
PO'I/ER SUPf'LY
COOLlI«> FAN
OFF
l
(JoIN IOIRCME
I
1
ON
I
t
PHOt£ OR TELfX
I
OFF
J
I
OVERTEMP Loo<.OU
Pi"IUi't:
w
I
I CD HEA1&R llGHT
j
STATUS LIGHT IS
LIGHT IS
I
I
00
UNPLUG Ale CORD FROM
WALL. WAlT ::I SECOH)S.
PLUG BAa< IN.
PHOt£ OR TELEX
::.MI I OIRCME •
1. OlEO( HEAD CABLE CONr-ECTOR
(STRAIGHTEN &NT PINS)
PHOt£ OR TELEX OMNIOlRCME
FOR INSTRUCTIONS.
II
1.
I
REM01& CONTROl FOR
STAI'a3Y MODE.
PHOf£ OR 1'VX (JoINIOfl'DE
FOR INSTRUCTIONS.
Q1E0(
00
I
1 • ALLOI'I SYSTEM TO RUN
(WAlT 10-1'5 MIN.)
PHOt£ OR TELEX
OMNIOIRCME •
Note:
When contecting Omnichrome. r
stage of this flow chart.
I
IS
j
ON
I
1. Q1E0( lASE R BENoi
FOR ElLoc::KAGE.
2. VIEW DlSOlAFGE
lHFIOI.JGH AI R INI..ET!
OR OUTLET. OBSERVE
DlSD1ARGE COLOR
CP.lN< OR BUIE)
PHOf£ OR 1& LEX
j
CMi I OIfOJ1E
3.2.
Check status ofthe green power supply Power-On status light for "on" or "off'.
3.2.1.
3.2.2.
3.3.
3.4.
If the Power-On status light is "off', continue.
3.2.1.1
Check AlC power to power supply - wall outlet, AIC cable
and connector; must be 104 to 128 Volts, Low Voltage will
not energize K 1, WB4.
3.2.1.2.
Check remote control circuits and interlocks.
3.2.1.3.
Check main fuse if Power Supply on back panel.
3.2.1.4.
Check Klan WB4 and associated AIC control circuits.
lfthe AIC status light is "on", and keyswitch is "on" (horizontal
position), go to Paragraph 3.0; otherwise turn keyswitch "on" .
Check status of the red power supply TEMP LOCKOUT light for "on" or "ofT'.
3.3.1.
If the TEMP LOCKOUT light is "off', go to Paragraph 4.0.
3.3.2.
If the TEMP LOCKOUT light is "on", continue.
3.3.2.2.
Check fan on laser head for correct operation. Check AIC
connector on fan . Fan should show a modest but steady
flow of air in the range of IOta 20 CFM.
3.2.2.3.
Does the ambient temperature exceed 100 F (38 C)?
Excessive ambient temperature can cause plasma tube
overtemperature circuit to activate.
3.3.2.4.
Wait for IOta 15 minutes with laser system turned on. AIC
power interruption will cause TEMP LOCKOUT which will
recover most rapidly with system (and head fan) turned on.
System will re-start and re-regulate automatically.
Check status of fan in laser head for "on" or "ofT'.
3.4.1.
If head fan is "off" this indicates a malfunction in the low voltage circuit
in the power supply. Check circuit associated with K2 on back panel of
PIS and U2 ofWBl.
32
3.4.2.
3.5.
If head fan is "on", go to Paragraph 5.
Check status of fan in power supply.
3.5.1.
If PIS fan is "off', continue.
3.5.1.0.
Check to see ifOVERCURRENT light is "on".
(Visible through louvers PIS cover). If
OVERCURRENT light is "on", unplug AC cable,
wait 3 seconds and plug back in. If
OVERCURRENT light comes "on" again, then an
overcurrent condition exists. Check 1 amp fuse (F8;
with connectors to left, it is the last fuse to the right,
next to blank position).
any rate, a blown tuse
results in an overcurrent condition. Overcurrent can
also be caused by a faulty or "weak" Q9 optocollplcr.
And, finally, a shorted Q2, MJ 10007 Transistor.
3.5.1.1.
Check low and high voltage connectors at rear of
power supply. IfH.V. Connector has an internal arcover, overcurrent light will come "on". If so
repotting is required. Interlock circuit in each
connector will inhibit high voltage circuit and PIS
ran. Look for bent, pushed back or arc damaged pins
and repair. Make sure BV plug has all ic)Ur red "0"
rings and is tightly mated to receptacle in PIS. Sec
that keyswitch is "on" (horizontal position).
3.5.1.2.
Check for correct laser head/power supply
combination. Series 39X, 56X, and 112X laser
heads can be used with any Modell 00 or Model
lOOA power supply. Series 74X laser heads can be
used only with a Modell OOB power supply.
3.5.1.3.
Check for failed components or fuses in the PIS. If
fuses are blown this indicates one or more failed
components in PIS. Fuses in circuit are to limit
damage due to failure toreplacement components.
Identity of blown fuses will approximately indicate
failed components. If main fuse is blown, there is
probably a major fault or short in the power supply.
If transistor base fuses on Q2, Q3, and Q4 are blown,
33
replace standard package of parts including: All
three power transistors (Q2, Q3 & Q4), two
2N2222's, the 6N 136, the SG3627, and the SN7474.
3.5.2.
3.6.
If PIS fan is "on", continue.
3.5.2.1.
Check PIS function using an alternate laser head if
available.
3.5.2.2.
Observe laser head and PIS for sound and/or visual
indications or arcing or smoking.
3.5.2.3.
Check BV connector for bent, pushed back or arc damaged
pins. Repair and remate firmly .
3.5.2.4.
Check Plasma Tube Voltage between outside terminal of
ballast resistors (R7i and R8) and chassis ground
(39~ 1,3K v, 56 ~2K v, these are cold tube voltages).
3.5.2.5.
Check Plasma Tube filament cold resistance, should be 0.9
+ 0.1 Ohm from ~ to Pin 12 on low voltage laser head
connector (P 1). If open circuit, change Plasma Tube
connection to alternate filament. Inside laser head cover
adjacent to output end of plasma tube. Common terminal
for "Normal" and "Spare" Cathode is marked with Black.
Open filament may indicate plasma tube is "up to air", IE,
has cracked glassware.
3.5.2.6.
Remove and inspect Plasma Tube for cracks or leaks, see
separate procedure.
3.5 .2.7
Install a new Plasma Tube per separate procedure.
-
Check status of yellow power supply Cd HTR light for "on" or "011".
3.6.1.
If Cd HTR is off, continue.
3.6.1.1.
Check remote control circuit to ensure unit is not in standby
mode and that external standby circuit is properly
implemented.
34
3.6.2.
3.6.1.2.
Is Cd HTR light blinking? Observe light for 2 to 3 minute
period to note changes and regularity of light intensity level
and ensure that light is truly ofI.
3.6.1.3.
Check Cd
triac (Q 1 on
(See Section 2.2.2 and 5.15).
3.6.1.4.
Check continuity of heater circuit in laser head. Heater
10
resistance should be 1.75 + 0.2 OHM 1rom Pin 8 to
of PI (Low voltage head cable, 16pin).
3.6.1.5.
Check 10M OHM tube voltage sampling resistor fiom PI, 4
to P2, 4 (High voltage 4 pin cable).
associated circuitry.
If Cd HTR light is "on", continue.
3.6.2.1.
Check optical system for beam blockage.
3.6.2.2.
Check Plasma Tube sidelight color by observing through
head fan aperture or air inlet aperture. A pink sidelight
color is normal. Blue sidelight color indicates shorted or
other problem with triac control circuit (Q 1 on WB2).
Check triac and associated circuitry and 10M resistor in
HV cable.
3.6.2.3.
Is Cd HTR light blinking? Observe light for 2 to 3 minutes
to note changes and regularity of light intensity level.
3.6.2.4.
For Series 39X remove top cover and manually deform the
(cathode) mirror flange all
to see if
output beam can be achieved. DO NOT TOUCH ANODE
MIRROR FLANGE AT AIR EXHAUST END OF LASER
I-lEAD. LETHAL HIGH VOLTAGES ARE PRESENT.
For Series 56X and 112X laser heads, see later section on
resonator alignment.
3.7.
Laser Output Power is low.
In order of increasing difficulty, perform the following:
35
3.7.1.
Check records on laser system. Is the laser output low compared to a
previous measurement using the same radiometer and measurement
technique?
3.7.2.
Review measurement equipment and technique. Is the radiometer
calibration current? Is the beam diameter too large or small at the
detector surface for an accurate measurement?
small beam can cause
overload of detector.
3.7.3.
Check for dirty or obstructed optical elements between the laser and
radiometer.
3.7.4.
Check for low NC line voltage. The line voltage should nominally be
greater than 104 VAC.
3.7.5.
Check the Jaser head cooling air now for blockage either at air inlet or
outlet.
3.7.SA. Check for loose plasma tube in laser head by gently shaking. Ifloose
perform procedures described later in Section 4.
3.7.6.
Check ambient temperature. Normal range is between 50 F and 100 F
(10 C to 40 C). Ambient temperature range is exceeded when Cd BTR
duty cycle reaches its limits of 20% (ambient too high) or 80% (ambient
too low).
3.7.7.
Check plasma tube discharge current (J 00 mA nominal). Read voltage
between black and blue test points on the back panel ofthe laser head.
Use a non-grounded digital multi meter . Measurement should be 1.0+/0.02 V (lVIlOOmA). Usual fault condition is Q9 failure causing greater
than 1.2V (or l20mA). Overcurrent LED inside power supply will come
on if tube current exceeds 112mA.
3.7.8.
Check plasma tube operating voltage to ensure operation within normal
range. Measure this voltage between the black and red test points on the
back panel of the laser head. Series 39X laser heads should read about
.9SVDC. Series S6X heads should read about 1.6VDC. If voltage is
outside of this range, check either the triac control circuit (Q 1 or WB2),
or the plasma tube reference voltage circuit (Terminal 9 of WB3 and
associated reference resistors R19 of WB3 and 10M reference resistor in
the head cable between terminalS ofWB3 and Pin 4 ofP2).
36
3.7.9.
I,
Adjust cadmium pressure adjustment potentiometer R2 on WB3
(accessible on rear panel of all 39X and 56X laser heads and on the side
of 112X laser heads. Pots are labeled Vt ADJ. Clockwise produces
increased plasma tube voltage which relates to decreased cadmium
pressure. Counterclockwise produces decreased tube voltage (increased
cadmium pressure). WAIT. CIRCUIT IS SLOW AND CAN TAKE 3060 SECONDS TO RESPOND. Note if laser output can
increased
with this adjustment.
3.7.10. Check plasma tube resonator alignment. See Section 4.0.
3.7.11. If none ofthe above procedures is adequate to bring the laser output
power up to an acceptable level, internal damage within the laser plasma
tube may be excessive. If this occurs within the warranty period, return
the laser head to Omnichrome where the plasma tube will be replaced at
no charge.
3.8.
Laser output power fluctuates or optical noise is excessive. In order of increasing
difficulty, perform the following:
3.8.1.
Monitor laser output and note frequency of output power fluctuation.
Very low frequency power output fluctuations in the order of 2 to 10
cycles per minute indicate instability in the cadmium pressure control
circuit. Moderate frequency fluctuations in the 10Hz to 50
frequency range are due to random plasma noise in the plasma tube.
High frequency fluctuations in the 250 KHz to 350 KHz range are due to
a plasma wave resonance in the plasma tube.
3.8.2.
lfthe laser output fluctuations are very low frequency 2-10 CPM this
can usually
eliminated by one of two procedures.
3.8.2.1.
Change the plasma tube voltage by + 10-20 volts using Vt
ADJ pot and monitoring voltage at the Vt test point on the
rear panel of the laser head. Note that test points measure
IV per 1000V of tube voltage. Wait 10-15 minutes
between each voltage change to see if output stabilizes. If
this procedure fails, continue.
3.8.2.2.
Put laser in standby mode for 10-20 hours, then return to
normal operation and monitor output stability. Repeat this
procedure, if necessary.
37
3.9.
3.8.3.
Iflaser output fluctuations are excessive in the moderate to high
frequency range (10 Hz to 350 KHz), this can normally be corrected by
adjusting cadmium vapor pressure (tube voltage). Low optical noise
generally occurs in a narrow range of tube voltage, so perform
adjustment carefully.
3.8.4.
If none of the above procedures is adequate, there may be a fault with
the helium pressure regulator which caused excessive helium pressure
within the plasma tube, or cathode damage has occurred. Change
cathode connectors on the plasma tube from the normal to 5pare cathode.
The common terminal for the normal and spare cathode is marked with
black.
Laser beam is distorted
The output beam from the laser exhibils excessive scatter or the beam pattern is
not uniform, the likely cause is contamination of the output laser mirror, by dust,
oil vapor or other foreign materials.
Cleaning of the output mirror is best done with acetone although alcohol is
sometimes adequate.
3.9.1.
Series 39X, 56X, and 74X optics cleaning:
Open the output aperture slide on the front of the laser head. Clean
exposed output mirror surface with "Q" tip or optical tissue and
acetone.
3.9.2.
Series 112 Optics cleaning:
Warning: The series 112 laser mirrors are
glass-to-metal
sealed into an anode assembly on each end ofthe laser. This metal
flange which can be seen as an annulus around the laser mirror is
operated near 2000 VOLTS. CLEAN OPTICS ONLY WITH
OPTICAL TISSUES OR Q-TIPS USING ACETONE OR
ALCOHOL AND ONLY USING A DIELECTRIC TISSUE
HOLDER. A Q- Tip is adequate for output laser mirror cleaning.
If laser output is only about 20 mW at 442 nm, check to see ifboth
power supplies are turned on. If both are on, check to see if both
discharge capillaries are lit by observing thru cooling fan.
38
Items 5.2.1,1, and 3 above can quickly be ascertained to a more
extensive field or factory evaluation. If any problems occur
beyond those described above, contact your nearest Omnichrome
representative for instructions.
39
40
SECTION 4.0
LASER HEAD TEST, ALIGNI'AENT & ADJUSTMENT
4.1
STATIC CONTINUITY TESTS
Every laser head has a 16 pin low voltage cable terminated by connector PI and a
4 pin high voltage cable terminated by connector P2. Inspect these connectors for
burned or pushed-back pins. Then perform the static continuity and resistance
measurements on a disconnected laser head using a high impedance ohmeter as
described in Table 1.
These measurements will not ensure proper operation of a laser head but will ensure that
no malfunction within the laser head can cause damage to a power supply.
Pl
pi
o
TADlEI
lASER HEAD CONNECTOR CONTINUITY AND RESISTANCE VALUES
ITEM
I.
2.
3.
4.
5.
6.
7.
B.
9.
10.
II.
12.
13.
14 .
15 .
16.
17.
18 .
19.
20.
21.
22.
MEASUREMENT POINTS
TO
FROM
1'1,4
1'1 , 1
1'1,4
1'1,2
PI,4
1'1 ,6
PI,S
1'1,8
1'1 ,8
1'1,11
PI,I3
PI , I 5
1'1,3
1'1,7
1'1 ,8
1'1,11
1'1,15
1'1,16
1'1,13
*-h
,I
P24
~
!I
PI,4
1,9
1'1 , 10
1'1,12
PI,14
PI,16
PI,4
PI ,4
1'1,4
1'1,4
1'1,4
1'1,4
1'1,4
.w.
:in:
..W1'1,4
PI,4
OHMS
Diode Test
3 to 5 K
20-21K FOR 39X
12-I3K FOR 56X
10K
FOR 74X
II-12K FOR 112X
5K
2.8
1.8
0.9
OJ
325
OlON 200
OLON 200
OL ON 200
01. ON 200
OL ON 200
OLON 200
OLON 200
<.3
OLON 200
OLON 200
OLON 200
IOMEG±5%
OLON 200
P I is the 16 pin low voltage connector. P2 is 4 pin HV connector.
41
COMMENT
(Forward Conduction)
HELIUM RESER VOIR HEATER
CAO RESERVOIR HEATER
CA THODE FILAMENT
HEAD FAN COIL
IS VTOGNO
CASE TO CKT GNO
IITRS TOGNO
I'lL TOGNO '
FAN TO GND
FAN TOGNO
INTERLOCK TO GNO
4.2
RESONATOR ALIGNMENT
Omnichrome He-Cd lasers have three resonator types. The Series 39X lasers
utilize the plasma tube itself to maintain alignment of the laser mirrors, similar to
state-of-the-art He-Ne lasers. Series 56X lasers use a 24 annealed Invar welded
structure. Series 112X lasers use a 48" annealed lnvar welded structure. The
procedure for the alignment of each type of resonator differ substantially.
If the laser output is zero or low and resonator alignment is suspected, first check
to ensure that:
1. Sufficient time has elapsed for the plasma tube to warm up.
2. No electronics problem exists such as tube anode voltage regulation.
3. Turn off the laser and remove safety key. Shine a nashlight into the helium
regulator assembly. Look into the output laser mirror and down the discharge
capillary to see if condensed cadmium in the condenser section of the plasma
tube has built up enough to internally block the laser beam. If so, remove the
blockage using the condenser remelt timer on the back panel of the head.
4. Inspect laser mirrors for internal deposits or films which are visible from
scattered light from the discharge. If so, remove films using procedure in
Section 4.3.
If the plasma tube appears to operating normally continue.
4.2.1.
Series 39X Resonator Alignment
Series 39X laser resonators are integral with the glass
tubes and
use adjustable flanges on the ends of the plasma tube for mirror
ali gnment.
Remove the front panel of the laser head by removing the screws which
hold the panel on the bottom of the laser head and the screws on each
side. If the laser output is lower than expected, manually deform the
output mirror flange all directions while monitoring laser output by
axially pushing with a finger around the edge of the 1.75 inch diameter
mirror flange. If one position causes laser power to increase, adjust the
appropriate set screw to maximize laser output. If laser power is not
adequately recovered by this process, check to see if the beam is
centered in the output laser mirror. If not, anode mirror adjustment may
42
be necessary. DANGER: THE ANODE LASER MIRROR
OPERA TES A T VOLTAGES OVER 1000 VOLTS. EXTREME CARE
MUST BE EXERCISED WHEN ADJUSTING
To adjust anode laser mitTor first remove the remote cooling cover plate
on the back end of the laser head. Do not leave cover plate off for a long
period of time since this will cause overheating of the plasma tube.
adjust laser mirror use a 1116 inch Allen wrench with well insulated
handle and shank. After removing cover plate, adjust laser mirror in
direction to cause laser beam to center in output mirror. This will cause
output to drop until the output mirror is readjusted for maximum output.
This process is repeated until best output of the plasma tube is achieved.
If the output remains low, recheck the introductory items of Section 4.2.
If no laser output occurs the procedure may require the use of an
autocollimator. Before this, perform the simple check of manually
deforming the output mirror flange to see if laser output can be
produced. DANGER HIGH VOLTAGE. If so, continue optimization
process described above. If not, refer to procedures in Section 4.3.
4.2.2.
Series 56X laser resonators are annealed lnvar welded structures. The
plasma tube is suspended in the invar resonator, held only at the mirror
flange ends which allow [or mirror alignment. All adjustment of the
resonator is performed using any of six nuts on each end of the three
invar rods.
Remove the front panel of the laser head by removing the appropriate
Also remove
screws on
sides and bottom of the laser
remote cooling cover plate on the back paneL
Inside you will see three nuts (3/8 inch) on each end of the laser
resonator. For each ofthese six visible nuts on the front and back of the
laser, there is a mating back up nut not visible on the inside.
If the laser output is lower than expected, manually deform the resonator
by pushing inward along the rod axis on each of the sixnuts. If one
location causes output to increase, adjust the appropriate nut to achieve
maximum output. "Walk" the resonator at anode and cathode ends until
maximum output is achieved.
43
If the resonator is badly out of alignment, it may be necessary to remove
the laser head housing to provide better access for alignment.
1.
2.
3.
4.
5.
Tum laser" off' .
Remove top cover of laser head by removing screws on
sides of
the laser head.
Remove the bottom cover by removing six nuts inside laser head
which hold resonator base plate in bottom cover.
Remove base plate assembly with back panel and plasma
tube/resonator assembly attached.
Tum laser "on" and repeat previous resonator alignment
procedures.
deforming resonator to see if laser output can be produced. If so,
continue optimization process described above. If not, refer to Section
4.3.
4.2.3.
Series 112X laser resonators are annealled lnvar welded structures. The
plasma tube is suspended in the invar resonator, held at each end and
also supported radially in the center. All adj ustmcnt of the resonator is
performed using any of the six nuts on each end of the resonator and
three radial set screws at the center of the resonator. The purpose of the
center set screws is to align the two separate sections of the laser
discharge capillary. The purpose of the 12 nuts on the ends of the
resonator is to align the laser mirrors with respect to the discharge
capillary and each other.
Remove the end covers from both ends of the laser head (3 screws on
each end). Exposed on each end ofthe laser head will be a 112 inch
thick ceramic plate to which the laser mirrors are mounted. These plates
are supported by three Invar rods clamped by six nuts.
If the laser output is lower than expected, manually deform the resonator
by pushing inward along the rod axis on each of the sixrods. If one
location causes output to increase, adjust the appropriate nut to achieve
maximum output. On Series 112 laser heads it is also necessary to
adjust the "center" of the laser. At the laser center the plasma tube is
supported by a set screw located directly under the hub of the cooling
44
fan. Two additional set screws are located 120 in either direction around
the head housing from the fan centerline. The screws located at 120 can
be accessed through holes in the housing.
CAUTION:
Use a 3/32
Allen wrench insulated with heat
except
for the tip for adjusting the 120 set screws. No high voltage is present
near these adjustment screws although access is through a low voltage
printed circuit board and contact can cause the plasma tube to
extinguish. Adjust these three "center" screws for maximum output.
r
deforming the resonator to see if laser output can be produced.
so,
continue the optimization process described above.
not, refer to
Section 4.3.
4.3
PROCEDURES FOR NO LASER OUTPUT
This section describes procedures to be used if no laser output occurs and all
electronics have been checked to be working properly.
No laser output can only result from one or more of four factors: Resonator
mirror misalignment, mirror damage, condenser blockage, or cadmium reservoir
depletion. If the plasma tube has been operated less than about 4000 hours
cadmium reservoir depletion is an unlikely occurrence.
Before attempting major realignment of the resonator mirrors check for
damage or condenser blockage. With the plasma tube "on" examine the output
surface. Films or
and rear mirror for films or particulate material on the
particulate material usually deposit in a circular pattern centered on the laser
mirror and are visible as a fog or high light scatter area dissimilar from the
remainder of the laser mirror. These films can usually be removed using a 500
Watt heat gun, but this procedure is performed with the plasma tube removed
from the resonator.
45
46
SECTION 5
POWER SUPPLY TEST AND ADJUSTMENT
REVISIOND
5.1.
PROCEDURE ESTABLISHES THE STEP BY
INSTRUCTIONS
ELECTRlCAL CHECKOUT OF THE SUPPLY, REVISION
5.2. EQUIPMENT
5.2.1.
Multimeter with clip-on test leads.
5.2.2.
H.V. test meter with 0-2V & 0-2KV ranges, with test leads.
5.2.3.
Oscilloscope with lOX probes.
5.2.4.
Resistive Load Box for preliminary checkout.
5.2.5.
8 Amp Variac and 500 Watt isolation transformer (before variac).
5.3. PRE-TEST
5.3.1.
Blowout the entire chassis with compressed air; look for any bits of
wire or solder left in the supply.
5.3.2.
Inspect for loose or missing hardware. Replace or tighten any found.
5.3.3.
Bend the 50 Watt, 10K resistors up into the air flow and see that none of
the wiring is touching the resistors.
5.3
Insert the required I.e.'s in their respective
optocouplers:
0UVJl''-'hl
use
tested
5.3.4.1.
Q4, 9, 26 = 50 to 1.00 Gain (4N25)
5.3.4.2.
= .25 to .65 Gain (6N136)
Q24
(add resistor between pins 5 & 7 to adjust gain: clip off pin
7 before installing I.e.)
5.3.4.3.
Insert fuses:
F1
F2,3,4
F5,8
F6,7,9
47
8.0ASB
= 3/8A
= 1.OA
=8.0A
=
5.4.
5.5
5.3.4.4.
Insert MJI 0007's with thermal compund and attach to heat
sinks with #6 x 5/8 sheet metal screws.
5.3.4.5.
For model 100 or 156, install following
Q23
= 2N2222
Q22
= 2N3020
U4
= 7474N
U6
= 3627J
AC LINE CHECK
5.4.1.
Continuity:
13, 7 to FI, 1
FI, 1 to K2, 1
FI, 1 to Kl, 1
FI, 1 to rotary Switch, SIA, Wiper
FI, 1 to PWB4-1, 1
5.4.2.
Switched AC Checks:
Kl, 2 to FANI (org) & CRt, (I-IV. Bridge)
K2, 2 to Ti, 2
K2, 4 to ,1
5.4.3.
Resistance Checks:
Cl(+) to Cl(-) + 10 Ohms
C19(+) to C19(-) = "aL"
C5(+) to C5(-) = "OL"
C8(+) to C8(-) = 3.56K+/-.25K(20K scale)
C9(+) to C9(-) = <.3 Ohm
C4(+) to C4(-) = "aL"
C3(+) to C3(-) = 190 to 225 Ohms (2K scale)
AC CHECKOUT
5.5.1.
Disconnect spade terminals from CRl, H.V. Bridge.
5.5.2.
Hook-up, AC, L.V., & H.V. connectors (from resistive load box) & use
adaptor if testing a Model 156 supply.
5.5.3.
Tum rotaryswitch to "Shutdown" position & plug AC cord into Variac
(KEY "ON").
48
5.5
With Variac at "0", turn Variac "ON".
5.5.5.
Connect Multi-meter (20V scale) across the 100u, 16 or 25V
PWB4-1
note voltage as Variac is
5.5.6.
With Variac at "10", meter should read approx. 1.8v. Ifnot, turn down
Variac & recheck connections.
5.5.7.
Record voltage reading when relay actuates (K3, <8v).
5.5.8.
Record voltage reading when relay drops-out (> l.5v).
5.5.9.
With Variac at "100", turn "ON"
out or "plug-pull".
"OFF" 10
on
a
5.5.9.1. Note 1/2 sec delay in K3, when turned "ON", & immediate response
when turned "OFF".
5 .6. CONTINUITY CHECK, K3 RELAY
5.6.1.
5.6.2.
Multimeter across Cl. (200 Ohm scale)
5.6.1.1.
Relay "OFF"
5.6.1.2.
Relay "ON" = "OL It
=
10 Ohms
Meter across C9.
5.6.2.1.
Relay "OFF"
5.6.2.2.
Relay "ON"
=
=
<.3 Ohm
"OL"
5.7. LOW VOLTAGE CHECKOUT
5.7.1.
Turn "OFF" Variac (rotary switch, "SHUTDOWN", and AC cord still
connected to Variac).
5.7.2.
With Variac at "100", turn "ON" Variac, then turn the Rotaryswitch to
"OPERATE".
0'
f
5.7.2.1.
Green "Power" Light should be bright and steady.
49
5.7.2.2.
If the Fan in power supply comes "ON", continue test. If
not, tum "OFF" Variac IMMEDIATELY, and check for
faulty components or solder bridges on WB 1. Also, look
folded-over "legs" on LC.'s.
5.7.2.3.
sink to circuit
Check U3, 5V regulator, for clearance of
board. Should be <1132". Lower U3 by heating all three
'legs' at once. After lowering, add a little fresh solder 10
each connection. Check [or no solder bridges.
5.7.3.
With Muitimeter, measure the following:
C 19 = 17 to 21 v (check polarity of capacitors).
C5 = IS to 20v
C8 = 5 +1-.lSv
C3 = 9 to 13v
C4 = 9 to 13v
5.7.4.
If all voltages check out, continue test.
5.8. FILAMENT VOLTAGE CALIBRATION
5.8.1.
Connect Meter (20v scale), (-) to PWB 1, 19.
5.8.1.l.
Adjust R2, on PWBl, to obtain 5.55v.
5.8.1.2.
See that all three I.c.s, on WB2, are tight against chassis
with thermal compound of both sides of mica washers. Use
2-56X1I4 screw with shoulder-washer & nut to secure the
I.C.s firmly to the chassis.
5.9. SWITCHING TIME CALIBRATION
5.9.1.
Using floating scope ground, connect probe ground
to PWBl,9 and
probe tip to top side ofRl18 (lOv/div, Su Sec/div, source: ChI) (be
certain the 'V AR' knob is clockwise to stop).
5.9.2.
The resulting waveform should have a period of24 to 2S uSee. (must
not exceed 25 uSec). See scope photo # 1.
5.9.3.
The period may be adjusted by RIll on PWBl.
50
5.10. CHECKING INVERTER DRIVE
5.10.1.
Using same probe ground (PWBl,9) place probe
side of fuses) (2v/div, 10 uSec/div).
on F3, then F4 (left
5.10.2. The waveforms should look like scope photo #2, and have a (+) peak
over l.5v, but <2.0v.
5.10.3. If peak level falls below 1.5v or over 2.0, Q3 or Q4 may be faulty.
5.] 1 CHECKING SWITCHER DRIVE
5.11.1.
Connect scope probe ground wire to PWBl, 13, touch probe tip to right
side of F2; waveforms should look like scope photo #3.
5.12. FULL POWER CHECK
5.12.1. Disconnect power cord from Variac, turn "OFF" Variac and reduce to
"0".
5.12.2. Connect power cord, with rotaryswitch in "SHUTDOWN", to AC Line
outlet (no isolation).
5.12.3.
Connect "cheater" cord to H.V. Bridge and plug into Variac.
5.12.4. Connect 2KV meier to chassis ground and outside end of 10K, SOW
resistors (+).
5.12.5. Connect 20v lead to (-) end ofC19.
5.12.6. Connect scope probe ground wire to PWB 1, 9 and probe tip to post #2
on Chassis (SOv/div, 10 uSee/div, set trace to next to bottom graticule
line).
5.12.7. Turn rotaryswitch to "OPERATE". Supply fan will come on.
5.12.8. Turn "ON" Variac and slowly increase, watching scope trace and
voltmeter (20v scale). See scope photo #4. If any oscillations or
instabilities occur, QUICKLY turn down the Variac. Otherwise,
continue.
51
5.12.9. At "80" on Variac, the voltmeter should read LOOv +/- .02v,
(l00=/-2rnA) and the scope trace should be about 280v and peaked out,
for a Model 139; at "60" on Variac, <250v, for a Model 100 or 156.
5.12.9.1. Any further increase in Variac setting should not
the scope
display or the voltage across R48 as displayed by the voltmeter.
the voltage continues to rise and reaches 1.10v, turn down the
Variac to "0". Ifthe reading is <.98v or >1.02v but <l.lOv, then
trim by adding resistors at R42 or R43 until the reading is in
tolerance (use decade box to determine value).
5.12.9.2.
Ifthe voltage remains at 1.00v+/-.02v, then increase Variac to
"1 00" (full 115V line setting).
5.12.9.3. Record voltmeter reading, then turn "OFF" rotaryswitch
momentarily. The reading should be .83v+/-.03v. Record reading.
DO NOT LEAVE ROTARYSWITCH "OFF" FOR MORE THAN
ONE MINUTE, while Variac is connected to CRl,
Bridge.
5.12.9.4. If operation checks out, then "snap" Variac "OFF", noting that
voltmeter goes to "0". Then, "snap" Variac back "ON" and note
that the voltmeter returns to the original reading.
5.12.9.5. Turn "OFF" Variac and unplug "cheater" cord from Variac. Turn
down Variac to "0".
5.12.10. Thermal Lockout Trip Points
5.12.10.1. Unplug AC cord from supply. Remove scope probe.
5.12.10.2. Disconnect "cheater" cord from H.V. Bridge. Reconnect spade
lugs to H.V. Bridge.
5.12.10.3. Connect multimeter, (-) to negative end ofC19; (+) to bottom of
R76.
5.12.10.4. ReconnectAC cord. Turn "ON" rotaryswitch.
5.12.10.5. Tube current should be lOO+/-2mA. Read multimeter on 2V scale
and record reading at "R
" on checkout sheet (should be
.25v+/-.003v).
52
5.12.10.6.
5.12.11.
5.12.12.
Tum Keyswitch "OFF" and record meter reading at
"S:
"on checkout sheet (should be .51-.54v). Turn
Keyswitch back "ON" and check: "KEYS WITCH
_ _ _ _" on checkout sheet. Remove AC
supply.
Overcurrent Check
5.12.11.1.
Connect decade box to R39 (both sides) with box set at
29000 Ohms.
5.12.l1.2.
ReconnectAC cord to supply. Tube current should be
approx. 108 rnA (1.08v). Slowly reduce the box resistance,
1K at a time, until tube goes out and red LED on the
Overcurrent board lights. Record highest tube current
observed, at: "O.c.
mA" on checkout sheet.
Should be J 14 to 116 mAo If not, change value of 68 Ohm
resistor on WB4-1 board; higher value = lower current, and
lower value = higher current.
He Hir Check
5.12.12.1.
Tum "ON" He Htr switch, located on Load Box. Both,
Load Box He Htr LED and power supply lIe Htr LED's
must light. Check step # 14 on checkout sheet this is so.
5.13. FINAL POWER SUPPLY CHECK
5.13.1.
Unplug AC cord and turn rotaryswitch to "SHUTDOWN" (OFF).
5.13.1.1.
Disconnect "cheater" cord from CRl, H.V. Bridge and
reconnect spade terminals to the H.V. Bridge.
5.13.2. Check and be certain that all switches (except Keyswitch) are "OFF" and
the Variac is at "0".
5.13.2.1.
Disconnect resistive load box from supply.
5.13.2.2.
Connect correct test "head" to supply.
5.13.3. Disconnect scope probe from PWB 1,9 and post #2 on chassis.
53
5.13.3.1.
Connect scope probe ground to RFI filter bracket.
5.13.3.2.
Connect probe tip to
1,22. This will allow viewing of
Cd heater waveform (duty cycle). (2mSecldiv,10v/div,Line
sync).
5.13.4. Connect the multi meter (-) to minus end of C 19 and (+) to top end of
R7i2 (Temp diode voltage). Use 2v scale.
5.13.5. H.V. meter is still connected: negative to RFI bracket, (+)2KV to
outside end of 10K, 50W resistors, and (+) 20v to minus end ofC19.
Now, by switching meter between 20v and 2KV, the tube current and
tube voltage may be observed respectively. Place air baffle over the
three heat sinks.
5.13.6. With rotaryswitch "OFF", plug AC cord into line outlet.
5.13.7. Rotaryswitch to "OPERATE": Tube lights in 2-4 seconds.
5.13.7.1.
Tube voltage should be near 1200v, for a 139, and around
2KV for a 100 or 156. Tube current should be 100+/-2mA
(1.00+/-.02v on meter). Cd light should come "ON". See
scope photo #5.
5.13.8. Tum rotaryswitch "OFF" momentarily. The voltmeter should read
0.82v+/-.03v (82+/-3mA). Cd light should go "OFF".
5.13.8.1.
Tum rotaryswitch "ON". Cd light will come "ON".
5.14. HE CONTROL
5.14.1. Test "Head" is set to cause the He Htr to come "ON" after a few minutes,
then go "OFF" as the tube comes up to temp.
5.15. CD CONTROL
S.15.1. Allow tube voltage to stabilize at 925-99Sv for a 139,1 and about 15501650v for 100 or 156. Will take 5-6 minutes.
S.IS.2. Diode voltage (temperature) should start at about .6v and will be in the
.35 to .42v range when tube is stabilized.
54
5.15.3. Tube voltage should be stable, with <2 volt variation.
70-80% at
5.15.4. Observe scope trace of Cd Htr duty cycle. Should be
start, and about 50% for a 139 and
35% for a 100 or 1
#6.
reasonably
stabilizing. See scope
steady.
5.15.4.1.
If waveform is steady with only an occasional "jump"
continue with test.
5.16. THERMAL LOCKOUT & SHUTDOWN TIMER CHECK
5.16.1.
Tum rotaryswitch "OFF". Cd light should go "OFF", 1 green power
light will remain "ON".
5.16.2. After 2 min, ] 6 sec. the tube should go out, and the red LED (temp
lockout) will come "ON".
5.16.3. At 2 min. 51 sec. all lights should go "OFF".
5.16.4. Tum rotaryswitch back "ON". Green and red LED's should come "ON".
5.16.5. After several minutes, red LED should go "OFF". Cd
"ON", and tube lights again.
should come
5.16.6. Complete checkout sheet and attach proper labels to the power supply.
See that proper SIN & Model # are on the checkout sheet. Place
checkout sheet in proper folder.
5.16.7. Apply RTV to terminals, 1,2,3,4,&7 of
Module, and to
Connector. Install red air baff1e over three heat sinks before placing
cover on supply (one screw only). Put rotaryswitch in "SHUTDOWN"
before placing on shelf.
55
56
SECTION 6
LASER MALFUNCTION REPORT
DATE,_ _ _ _ _ NAME,_ _ _ _ _ _ _ _TELEPHONE
OWNER INFORMATION:
COMPANY NAME,_ _ _ _ _ _ _ _ _ DIVISION
ADDRESS
CITY_ _ _ _ _ _ STATE,_ _ _ _ _ _ZIP CODE
------LASER SYSTEM INFORMATION:
LASER HEAD
POWER
SUPPLY
MODEL NUMBER
SERIAL NUMBER
MALFUNCTION INFORMATION:
1. TOTAL OPERATING HOURS: ESTIMATED
TIME METER- - 2. PLEASE CHECK OFF ALL APPROPRIATE MALFUNCTION SYMPTOMS
BELOW:
_ _ Cl - LASER SYSTEM WILL NOT START UP
_ _ C2 - LASER SYSTEM SHUTS ITSELF OFF
_ _ C3 - LASER TUBE WILL NOT LIGHT
_ _ C4 - NO LASER OUTPUT
___ C5 - LASER HEAD ARCING OR EMITS SMELL
_ _ C6 - POWER SUPPLY ARCING OR EMITS SMELL
_ _ C7 - LOW LASER OUTPUT (POWER:
mW)
_ _ C8 - OUTPUT POWER FLUCTUATES (TIME PERIOD, MINUTES PER
CYCLE
).
_ _ C9 - HIGH OPTICAL NOISE: RMS%
P-P%
57
3. DESCRIBE MALFUNCTION: SOUND, VISUAL, SMELL, ETC.
4. DESCRIBE OPERATING ENVIRONMENT: VIBRATION, SHOCK,
TEMPERATURE
5. DESCRIBE CONDITIONS PIUOR TO MALFUNCTION: UGIITS DIMMING,
ETC.
6. LIST ANY COMPONENTS OTHER THAN LASER SYSTEM WHICH
MALFUNCTIONED PRIOR TO OR SIMUL TANEOUSL Y WITH LASER
7. HAS TIllS LASER HEAD REQUIRED PRIOR SERVICE?
8. HAS THIS POWER SUPPLY REQUIRED PRIOR SERVICE?
58
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Omnichrome HeCd Laser Manual

Transcription

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