1 Philco Jr. Superheterodyne Model 80 Restoration 03/10/2013

Philco Jr. Superheterodyne Model 80
Restoration
03/10/2013
Purchased radio on Craigslist for $50. It was actually receiving one AM station when I
arrived to pick up the unit and sounded pretty good. There may have been previous restoration to the
electronics for it to still be playing!
3/11/2013
Inspection: water damage to lower sections of cabinet, can see some discoloration of
the wood and warping of the veneer and under layer. Not too bad, may be able to inject some glue into
the areas where the wood splits and clamp. Chassis shows some rust. Original grill cloth I believe and in
decent shape with only one small tear in it. May be able to apply some tape or glue to the back side to
make a repair without having to find a replacement grill cloth?
In looking at the bottom of the cabinet and removing
the 3 screws that hold the chassis to the cabinet it
appears that someone has drilled an extra hole near
the back center and an additional one at the front right
(facing the front of the radio) to accommodate a
different chassis? Perhaps the original chassis was
damaged by the water and replaced?
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Took off the two Rosetta knobs. Large tuning know still has the tensioning spring, small on-off/vol is
missing the tensioning spring. Prior owner stuffed in some aluminum foil/plastic for tensioning.
Removed the 3 speaker mounting nuts and pulled the speaker off. Cone is not torn! Top mounting
nut came from the top Rosetta mounting screw seen in the front of the radio. The bottom two
speaker mounting nuts came off different screws than the Rosetta screws.
Removed the two remaining nuts holding the grill cloth on, these nuts are on the two lower Rosetta
screws seen in the front of the radio.
Numerous pics of chassis taken. Appears to still be original?
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Removed tubes including tube shield on one of the 37 tubes (philco globe). Other 37 tube
pulled the grid cap off while removing the grid cap connector. May be able to repair, have new
37 & a new 42 on order just in case.
Removed frequency dial via set screw on the shaft of the variable cap. This to protect against
damaging the dial during clean up. All I’ve read about the cleaning of these types of dials is
“
D
O
N
’
T
”
.
W
a
t
er apparently washes off the ink. I gave it a light dusting and called it done.
Removed the dial lamp shield (fits over the lamp and its socket) and the dial lamp so it doesn’t
get damaged in cleaning.
3/18/2013
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Began making a few preliminary measurements of resistors and coils.
Removed power cord. Attached to on-off pot and center lug of cap block #32 (part#3793R).
Also connected to center lug of cap block #32 is a white (yellowish) lead from power
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transformer. (see photo a couple pages back). RESTUFFED cap block #32 with Y2 .015uF cap
(between lead #1 and lead #2(center lead) on cap block) and a .015uF orange dip cap.
Unsoldering leads to electrolytic cap #35’s outer lug. This outer lug connects through resistor
#36 to ground and has the following leads connected to it: a) negative lead for cap#34, b) center
tap lead #4 on power transformer (even though the schematic incorrectly shows this going to
ground), c) wire to lug of cap block #27 closest to the mounting bolt this lug also has resistor #26
connected to it, d) center tap #9 of power transformer. NOTE: a) and c) are the same wire,
stripped in center for connection to cap #35 outer lug.
Unsoldered power xformer leads to rectifier filaments (leads 7 and 6). Lead 6 is also connected
to the positive side of cap #34.
Unsoldered power xformer leads to filaments of output tube. (this also unsoldered the leads
that take power to the 2nd detector tube filaments.)
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Note that on-off/volume control (Part #7439, a 20k pot with switch) seems to be a replacement
since the shaft is too small for the Philco knob. Potentiometer
slider does not work well, may need to replace if it does not
clean up.
Removed xformer from the chassis by unscrewing the 4 screws.
Cleaned it up w/ alcohol and mineral spirits and put a light coat
of auto wax on.
1. Unsoldered speaker from chassis (at the speaker). Labeled
leads as left, center and right as photographed.
2. Unsoldered dial light leads, labeled “upper light” for lead that
goes to lug on top of light connector. [REPLACED dial light
leads]
3. Unsoldered leads to tuning condenser so I could remove the
tuner. Labeled the leads front & back tuner. Front is closest to
front of chassis. Removed tuner by unscrewing 3 screws from bottom of chassis [REPLACED
tuning cap and resoldered front & back leads]
4. Had to remove the on-off/volume pot to get at the third tuner screw. Unsoldered the antenna
wire which went to the 20k ohm end of the pot, the gimmick wire went to the wiper of the pot,
and other end of the pot was soldered to ground. Deoxit on pot cleaned up the wiper although
there seems to be a bad spot about midway in the swing.
5. Unsoldered the two grid caps for the 36 tubes going to the two coils, this so I could remove the
coil shields for cleaning and polishing. One of the grid wires was taped with old electrical tape
as part of a repair, this lead was clipped and will be replaced, may replace both grid cap leads.
6. Removed #34 capacitor. Removed lead from speaker that connected to + side of #34 as well as
a lead between + side of #34 and rectifier filament that also connects to lead 6 of power xformer
(this short wire is in the envelope with the cap#34 screws). Positive lug on cap#34 is colored
blue.
7. Removed cap#35. Was able to unscrew the center positive lug of cap #35 and leave the wires
on it. NOTE, outer lug is negative and is the case of the cap. Outer lug and case are insulated
from the chassis and ground with an insulating sleeve between the outer mounting bracket and
the case. Scanned the Philco label on this cap for use in case the clean up destroys the original
label (40mm x 16mm).
[RESTUFFED CAP 35 WITH 4uF and
REPLACED IT into chassis with two screws into chassis]
8. Resistor values
o #26 554k (spec=490k)
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o #22 244k (spec=240k)
o #20 11.4k (spec=10k)
o #19 1.4M (spec=1M)
o
9. RESTUFFED ALL BAKELITE CAP BLOCKS.
10. Replaced all wires, cap blocks, xformer, tuning capacitor etc. Upon trying to power up the radio
I heard absolutely nothing. Unplugged and started tracing wires to be sure I had wired things up
correctly. In doing the tracing I found that cap block 7762-B (which was discontinued and
according to Philco Service Bulletin No. 289 "Universal Bakelite Condensers is equivalent to
7762-OEU. 7762-OEU has 2 capacitors in the block wired with 0.001uF between lugs 1 & 3 and
0.015uF between lugs 1 & 2 and lug 1 is ungrounded. However, the bakelite block in this 80 Jr.
has lug 1 grounded and to match the schematic the 0.001uF is wired between lugs 1 & 2 and the
0.015uF is between lugs 2 & 3! When I made this change I began to get sound from the speaker
but there was a motorboat sound across the tuning span. I could hear one station (WAEB)
under the motorboating. After some discussion on the PhilcoPhorum I was checking voltages
and found that the motorboating disappeared when I would touch the plate of the Det-Osc.
This eventually lead to placing a 0.1uF cap across cap #10 (connected to the screen grid of the
2nd Detector tube. This eliminated the motorboat sound and I was able to tune in some
stations. I took that cap block apart and found had wired the block backwards, instead of the
caps being across lugs 1&2 and 1&3; I had them as 1&3 and 2&3. With this correction the set
played and after alignment seems to be working well. Voltages:
11. I did not mention the chassis. There are debates on-line about whether to paint a chassis or not.
The main argument against it is that the chassis was meant to have electrical contact with some
of the components (often ground) and that is difficult with paint. The main argument for is that
some chassis are so rusty that the only way to check the rusting is to prime and paint. With this
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chassis there was some rusting taking place and after watching Bob Andersen's youtube on
restoring his Model 60, I decided to take the rust off with naval jelly (and also with some wire
brushing with the dremel tool). Then primed with
rustoleum and painted with rustoleum aluminum. I used a
brush rather than trying to spray. Came out looking OK.
12. Began working on the cabinet. Took off the trim at the base of the cabinet, removed the
internal glue blocks and pulled the round cathedral top away from the front just enough to let
me inject glue into the sides where the veneer has bubbled. One small piece of veneer broke
away during this operation (on the back side of the front panel.
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13. Eventually I took the entire cabinet apart to try and fix the delaminating and bubbled veneer. I
was only partly successful, one side still has some bubbled veneer due to the cabinet having sat
in water at some point in its life.
14. Stripped old lacquer finish off with 50/50 acetone/lacquer thinner.
15. Tried bleaching the water stain with oxalic acid for about half an hour but there seemed to be
no change. Also bleached the center section with household bleach for about half an hour.
That did lighten it up some but the stain is still clearly visible. I think I'll just hope the toning
lacquer covers it up.
16. Sanded the entire cabinet lightly with 220 grit and then reassembled the cabinet.
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Replaced the grille cloth with one that is not like the original (reproductions of which are no
longer available) but it looks good. Used 3M 77 spray adhesive on the frame, stretched the grill
cloth on an embroidery hoop and glued it down. (Then realized I had forgotten to put the two
speaker mounting screws under the grille cloth so I had to pull it up and glue it back down.)
17. Sprayed on Deft Sanding Sealer (2x)
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Final Picture
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