Eico ST-84 Manual

STEREO PREAMPLIFIER
MOD E L
ST84
INSTRUCTION
MANUAL
ELECTRONIC
3300
NORTHERN
INSTRUMENT
CO.
BLVD .,
L.
I.
CITY
I,
INC .
Y.
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TABLE
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OF CONTENTS
SEC T ION l. GE NERAL DESCRI P TION AND
SPE CI FI CATIO NS
1- 1. Gene ral De s cr iption
1- 2. Featur e s
1- 3. Spe ci fi cati ons
Page
2
2
3
SEC T ION II. ME CHANICAL INST AL LATION
2-1. Gene r a l. • • . . . • . • • . .. • . . . . . • . . . . .. • . . . . 3
2 - 2. Console Mounti ng
3
2-2(a). P r epa r a ti on 01 Unit
3
2- 2(b). P r epa r ati on 01 the Ca binet . • . . . • . . • •.. 3
2-2(c ). Mount ing the Unit . . • . •• . • • . .• . •• . .... 4
4- 16. Li st enin g to a Monophoni c Source
Conne cted to Tape 2, Aux. 2, o r to
AM
IO
4- 17. Li s tening to a Ster eo phoni c Sou rce
Conne cted to Tape 1 and 2, Aux. 1
an d 2, AM an d FM • . . • . . . • .• • . . . . . • . . 10
4- 18. Ma ki ng Re co r dings
,
10
SEC TION V. MAINT E NANCE
5- 1. Gen e r a l
10
5- 2. Tr ouble -Sh ooti ng Pro ce dur e s
10
5-3 . Transfor me r Te mpe ratur e . . . • . . . . , . . , .11
SEC TION VI. E ICO' S SERVICE POLICy • . . . • . . . . . 14
SECTION VII. PARTS LIST
20
SE CT ION III. E LEC T RIC AL INSTALLA TIO N
3- 1.
3-2 .
3-3.
3- 4.
3-5.
Input Conne ctions . . . . . .. . . . .. • •. . .. . • . . 4
Output Conne ctions . . . . .... . .. • .... . . . . . 5
Power Conne ctions
5
Hum Adju s t ment
6
Powe r Amp Lev el Adjustment •• . .• . . . .. .6
SEC TION IV. OPE RATION
4- 1. Pr eli mi nary
8
4- 2. SELECTO R Swit ch Ta ble
8
4- 3. MODE Swit ch T ab le • •.. ••.• • . • . . •. • •. . •8
4- 4. Le vel Con tro l
9
4- 5. Bal anc e Contro l.
9
4- 6. Lou dness Slide Swit ch
9
4- 7. Ba s s Contro l (CH. t and CH.2 )
9
4- 8. T r eble Control (CH. I a nd CH. 2)• . • •. • •. .•9
4-9. Lo Filler Sli de Switc h . •.. • • . •• . • • . • • . • •9
4- 10. Hi Fi lt er Sli de Switch
9
4-1 1. Ta pe Monito r Slide Swit ch .. . ... • • . . . . •10
4- 12. Tap e Equali z ation Sli de Swit ch
10
4-1 3. Listeni ng to Phonograph
10
4- 14. Li st enin g to T ape De ck . .. .. . . . •. . .. . • 10
4- 15. Li st e ning to a Monophonic Sourc e
Conne ct ed to Tape I, Aux. 1, or to
Monophoni c FM Br oadcas t
10
ELECTRONIC
INSTRUMENT
co .,
FIGURES
SECTION I. GE NERA L DESCRIPTION AND
SP EC I FIC AT IONS
Fi g. I - I. ST - 84 P hoto
, Fr ont
SE CT ION III. E LEC T RIC AL INST AL LATI ON
Fig. 3- 1. Rea r Pane l Conne cti on s
Fig. 3- 2. Input Level Contro l Connec tio n
Fig. 3-3. Power Amp Conne ction
5
7
7
SEC TION V. MAINTENANC E
Fig.
Fig .
Fig.
Fi g.
Fi g.
Fig.
5- I.
5- 2.
5-3.
5- 4.
5- 5.
5- 6.
T r ouble-Shooti ng Ch ar t . . . • • . . . ... • 11
Voltage and Re s is tanc e Chart
12
Tub e La yout (Top Ch a s si s View)
13
Bottom Cha ssi s View . • . . • . . . • • .. .. 13
ST -8 4 SWit ching Table s .. . • . . . ... • . 18
ST - 84 Sche mati c Dia gr am . . • . .. . .. 19
IN C.
33-00 NORTHERN BLVD., L. I .C .1, N. Y.
(O,ftIGH f C 19 1>1 H ICU O NI( I"'\U U""ENT ( O"""'.N 1'.
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PAGE 2
~ ST-84
SECTION L GENERAL DESCRIPTION AND
SPECIFICATIONS
1- 1. GENERAL DESCRIPTION
Th e EICO Model ST84 is a co mple te high fid elit y
stereoph oni c control ce nte r . It offe r s practically ev ery
cont ro l and switching facili ty anyon e co uld want in a
physical design adapt able to an y typ e of in stallation .
With it you can se le ct , pr eamplify and cont r ol accu-
I
be con nected. P ermits the use of bo th a tu rntable and
a record changer in the ins t allation . One pair presents
47K ohm loa d and th e other pair l OOK ohm load, to
cover most popular cartridges. RIA A equalization.
2. Prov ision for connecting stereo tape hea ds .
NARTB equ a li z atio n for 7-112 and 15, or 3-314 ips
tape spe eds.
3. Stere o mi crophone inputs .
rat el y, an y s te r eophonic sour ce, wheth er it be from
tap e, di s c s or broadcasts. Faciliti es ar e co mprehe ns ive, includ ing t wo mag ph one inputs, a s e ven position
mod e s el ector, tap e mon it or, a nd high and low frequ ency
filt ers . E very control fa cility is both us eful and ef f ective.
For a ll fun ctions of the preamp, a ll ty pes of di s tortion ar e down to 0.05% at all levels. Re gardless of
price, no pr eamp ca n off er audibly lower distorti on.
For all basic functions (ma g ph ono, tuner, tap e ), hum
and noise is down to 0.05% or better, of the average
program level.
Pre s ent-day low lev el audio tubes e mplo y coiled
hea t er co ns tr uc ti on and ar e far less susceptible to hum
than they were ye a rs ago, when a de filament supply
was the on ly answer fo r r eally low hum level. In the
ST84, the total of hum and nois e is .0005 of th e av erag e
program le ve l. If a dc filament supply were us ed ,
this figur e mi ght be redu ced to . 0003, hardly a signifi cant improvement. Furthermore, th er e is an un fortunate aspect t o a dc filament s upply that is not
ge ner a lly r e aliz ed. If a heater-cathode sho rt should
deve lop in one of th e tubes, hum will immediately be
evident with an a - c filament supply and th e tube can
ea s ily be spot t ed and replaced. If the same thing
happen s with a d-c fil amen t su pply , no hum wi ll be
evide nt ; howev er, th e ope r a ti ng bias of th e tub e will
be changed by the presence of th e d c filamen t voltage
at th e ca tho de and distortion will r esult, whi ch may
not be immediat ely r ealized and will obvious ly be
more difficult to track down. In the Model ST -8 4, an
a- c filament supp ly is us ed, biased to a d-e potential
to minimize s usc eptibility to a -c le aka ge,
The ST 84 is s e lf-powered, for better performance
and convenie nce . It uses a full-wave rectifi er tube
po wer su pply. It works in conjunction with any high
quality basic stereo power amplifi er, such as th e E ICO
HF86, HF 87 and HF89, or with any two high qua lity
pow er amplifiers such as th e EICO H F1 4, HF 22, HF30,
HF35, HF50 and HF60.
1-2. FEATURES
1. Provision for two stereo phono car tridges to
4. High leve l input pairs fo r multip lex adaptor,
preamplified and equa li zed tape, FM tuner , and AM
tuner.
5. Versatile Mode Se le ct or chooses ster eo and
stereo r ever s e functi ons. Positions for sum of channe l l and chan nel 2 inputs to channe l l output, and sum
of channel l and channel 2 inputs to channel 2 output,
used for stereo ba lancing. Positions fo r channe l 1
input to channel 1 and channel 2 outputs, chan ne l 2
input to channel l and channe l 2 outp uts, and for mono
records, th e sum of channel l and channel 2 to chan ne l 1 and chan ne l 2 ou tputs, all for versati le mono
playing.
6. Separate level a nd balance controls.
7. Switched high and lo w fr equency filter circuits
permit e li mina ti on of rumble problem or scratch and
di stortion when ne ed be .
80 Switched loudne s s compensation.
9. Tape monitor swit ch.
10. F e edback eq ualization, with fe edback around
both preamplifier stages. High overload point.
11. Three-stage independent bass and tr eb le control ci r cuit s in each channel. They are of th e variable
infle ction point, feedback type fo r exceptionall y low
distortion an d the most desirable control character i s tic s. Th ese controls do not affe ct the volu me or
interact with each other, and boost or cut at t he extremes of the audio r ange do not aff ect the mid -range.
12. Separate filament windings and hum balance
controls fo r each channe l permit an optimum hum
bala nce for ea ch channe l, r a th er than a compromise
for both channe ls.
13. Unused inputs grounded by SE LECTO R switch
to e liminate cross -talk, except for TAPE input s , since
some tape machines are adversely aff e cted if playback
outputs a re grounded during recording.
~ ST- 84
1-3. SPECIFICATIO NS
Fr equency Response: ± 0. 3db 5-2 5,000 cps at any level
up to 3V RMS out. (Measur ed
from high level inp uts with level
controls s et at maximum and
tone contr ols e lect rically fla t.)
Hum & Noise:
Mag Phono and Tape Head: - 65db at 10mv in.
Tun er, Ta pe, Aux.: - 75db at O.5V in.
Sensiti vit y (mini mu m Ik e input for I V out. ):
Mag Phonos : 1.6mv ; T ape Head:
tmv
Micr ophon e: 2.8mv
High Lev e l Input s (tune r, tap e, aux.) : 0.1 7V
l
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PAGE 3
easy interchanging of s ystem co mpone nts for co mpa r i s on. If antennas ar e strung ar ound th e back of th e
console in which th e preamplifier is installed, a r range
them s o th ey will not interfere with a ccess to the unit.
7. ACOUSTICAL ISOLATION: If pr ea mplifl er and
sp eaker a r e installed in the same ca bine t (not r eco mm end ed), pr ovi de suffici en t s eparation to minimize
m echanical speaker vibration r eaching th e preamplifier
whi ch may result in mi croph oni cs and howling. The
minimum separation is about on e foot . A baffle, usually
the preamplifier mounting sh elf, sh ould be present
between preamplifi er and speaker. In ext re me cases,
it ma y be necessary to mount th e preamplifier on spon ge
r ubber ~ads .
2- 2. CONSOL E MOUNTING
1M Dis tor ti on (60 and 7000 cps at 4: I ): 0. 04%at 2Vout.
2-2A. PREPARATION OF UNIT
Harmoni c Distortion (20-20,000 cps ): 0.05% at2V out.
Tone Control Range: At 10kc: 15db boo st, 15db cut ;
At 50 cps : 15db boost, 15db cut
Equali zati on: Phono - RlAA; Tape Head - NARTB for
15 ips and 7-1/2 ips, 3-3/4 ips
Output to Tape Recorder Impedan ce: Sa me as sour ce
(tuner, etc. ) feeding pr eamp
Output to Main Amplifier Impeda nce : 8,000 oh ms
1. Turn unit ove r and loos en th e fr ont an d r ear
pairs of s crews (4 in all) tha t fasten the bottom plate
to th e s id e pi eces. Th en tur n th e unit ba ck right side
up.
2. Re move th e 4 s cr ews, two on each side, t ha t
fasten th e cove r to th e side pi eces. Remov e th e cov er
a nd s et aside.
3. On the top side of th e cha s s i s , loos en a ll 4
screws (2 on each s id e) that fast en th e chas s i s to th e
side pi eces.
Tub es: 5- 12AX7/ECC83; 1- 6X4
Siz e: 5- 1/2" hi gh, 15-7/ 8" wid e, 8-3/4" deep
Weight: 8-1/2 lbs,
SECTION II. MECHANICAL INSTALLATION
2- 1. GENERAL
1. Mount hori zont ally on a we ll -braced sh elf .
The stock thi ckn ess of th e wood pan el may not exceed
3/4".
2. Do not r emove fee t for mountin g. Air must be
allow ed to ente r through the perfor a ti ons in the botto m
plat e to avoid ove r heating.
3. Any sh elf abov e the unit must be spaced away
at lea s t 2 in ches. All ow at lea st a I- inch space on each
side of th e unit.
4. Leave th e ba ck of th e cabine t e s senti all y open.
5. EASY ACCESS TO CONTROLS: Mount th e pre amp lifier at a height whi ch will permit eas y ma nipu la tion of the co ntro ls .
6. ACCESSIBILITY TO PARTS: Tubes ar e th e
most fr equ ently r eplaced it ems in electronic equip me nt.
If the preamplifier is installed in a conso le, sufficient
space sh ou ld be a llot ed to r each and r emove any tube
in the unit. Fu r th ermor e, input an d output terminal s
of the preamplifi er should be ac cessible to permit
4. Push both s id e pi eces ba ck as far as they will
go. The s crews that have been loos ened will move
fr om the fr ont to th e r ear ends of th e slot s in th e cha s sis a nd th e bottom plate. Th en r e-tight enall th e s crews
that have been loosen ed . Check to s eethatall th e tubes
are prope rly seated in th eir sockets and th en r epla ce
and r e-fa st en the cove r to th e s id e ext r us ions .
5. Deta ch all th e knobs from th e cont r oi shafts
and th en r emove t he 4 s crews, (2 previously conce ale d
by knobs and 2 in th e r ecessed ar ea) that fasten th e
panel to th e chas si s . Wt the panel out over th e co ntrol shafts and set it as ide . Th e unit is now prepared
for ca bi ne t insta Hatt on,
2-2B. P RE PARATI ON OF THE CABINET
1. Two templates a re provided, one fo r th e ca binet
sh elf and th e oth e r for the cabi net pan e l, The sh elf
te mp late is used to locate exactl y t wo holes th at a re
to be drill ed in th e sh elf. The panel templa te is us ed
to locate exact ly the r- equ lred r ectangula r cut - out. The
two t emplat es mu st be us ed t ogether a s indi cated, a s
the r e i s a n exa ct r el ationship be tween the locati ons of
the s helf hoi es an d pane l cut -out .
2. To use th e sh elf te mplat e, cut it or fold it back
exactly a long the dashed line that corresponds to the
panel thi ckn ess. Remove th e sh elf fr om th e cabinet
and lin e up th is da sh ed lin e on the te mpl at e with th e
front edge of the sh elf, positionin g it al so a long the
edge to l ea ve at least i - inch cl earance on each s id e.
Tape the t e mplate in position an d use a center pun ch
to mark th e ce nte r s of th e two hol es to be drilled. If
mm ST- S4 I
PAGE 4
th e s he lf can not be r e moved, place th e t e mplate in a
s imilar manner on the to p si de of the shelf if th ere is
r oom to drill from th e top side, or on th e und erside
of sh elf if ther e is only r oom to dri ll from th e und er side. If th e t e mpla t e is us ed on t he unders ide of the
s he lf, mark th e r ear edge of the sh elf a t the pot nts
where th e ext ended heavy lin e s on th e templ at e hit the
r ea r shelf edge. Afte r th e hol es ar e ce nt er - punc he d,
r emove the t emplate and drill carefuliy th r ough th e
punched cente r s to a diamet er of 1/4". If the sh elf
has be en removed for th e drilling operati on, now r emount it. Finally, r eplace th e shelf-templat e in exa ctl y
its former po sition on the to p -side of th e s helf an d tap e
i t down.
If the shelf te mplat e has been us ed on th e
und er side of a stationary sh elf , now pla ce it on th e
top -side of the sh elf using the marks on th e r ear edge
of the sh e lf previous ly mad e, (In th e la tt er case,
accu racy may be impr oved by cutting th etwo ho les out
of th e sh ell -template with a r a zor blade an d then li ning
up th e hol es in th e sh ell-template with the hol es in
the sh elf ).
3.. To use th e pan el t e mp late, cut it or fold it
ba ck exactl y along th e da sh ed line. This dashed lin e
co r re sponds to the junction of th e top s ide of th e cabinet
s he lf and the int erior side of th e wood panel. Positi on
the pane l template ag ai n st th e inte r ior side of th e wood
pane l so that the dash ed lin e r ests against the s he lf
and the two heavy vertical lin es in the panel templat e
meet with the two heavy horizontal lin es in th e sh elf
t e mplates . Tape th e pa ne l template down a nd us e a
ce nte r - punc h to mak e th e ce nte r s of th e four 3/ 8" hol es
in the four co r ne rs of th e r ecta ngul ar cut -out s hown
on th e te mplat e. Now r emove both te mplates and drill
ca refull y th rough ea ch of th e four punched cent ers to
a hol e diamet er of 3/S" . On the fr ont side of th e wood
pane l s cribe a r ectangl e ext e r na ll y tangential to th e
four drilled holes. Check th e height and width of th e
r ec ta ng le again st th e pan el te mplate dimens ions. Th ese
dim ensions sh ould not be exceede d. Now ca refull y cut
out th e r ectangle with a sabre saw, using a s ma ll blad e
to s ta r t accur at ely in th e 3/8" holes. Aft e r t he cut ti ng
ope r a tion, an y r ough sp ots or excess mat er ial a long
th e edge s of th e cut -out may be r emoved wit h a fil e.
Finally, br ush or blowout a ll chips and sawdus t.
2-2 C. MOUNTING THE UNIT
1. Ins e r t t he unit f ro m the r ear of the ca binet,
ca refully gui ding the co nt ro ls th rough the pan e l cut out. Cente r the unit in the cut -out an d r e- mount th e
pan e l with th e four s crews pr evious ly r e moved.
2. From th e r ea r of th e ca binet, pull th e ampli fi er
to war d you gently , until th e fr ont panel is flush a gains t
th e wood panel.
3. Now place 5/S" flat washers against th e hea ds
of th e two No.8 x 1- 3/4" scr ews provided a nd ins e rt
th em fr om th e bottom side of th e s he lf into th e t wo
hol es dri lled prevtously . It may be neces s ar y to s hift
th e uni t s ligh tly to th e left or r ight in or der to afford
cl ea r access for th e s cr ews. When both s cr ews ha ve
cau ght, tighte n th em to s ecur e the un it to t he she lf.
4. Repla ce th e knob s previ ou sly r emoved on th e
cont ro l shafts.
SEC TION
nr, E LEC T RICAL INSTALLATION
3- 1. INP UT CONNECTIONS
Chan nels I and 2 ha ve 7 inputs eac h.
Th e cha nne l l inputs a r e ide ntified by th e suffi x
" 1" and are as fo ll ows :
CH.I Low Lev el Inputs
CH. I High Le vel Inputs
PHONO A I
PHONO B I
MlC I
TAPE HEAD I
FM
AUX. I
TAPE I
The cha nne l 2 inputs a r e id enti fi ed by th e suffix
" 2" an d ar e as follows:
CH. 2 Low Level Input s
CH.2 High Lev el Inputs
PHONO A 2
PHONO B 2
MIC 2
TAPE HEAD 2
AM
AUX. 2
TAPE 2
All hi gh le vel inputs provid e th e same ga in a nd
flat fr equ en cy r esponse. Low level inputs provide
mu ch hi gher ga in and th e prescribed gain- fr equ en cy
cha racteristics of RIAA for phono and NARTB for tape
hea d.
Monophoni c s ource s , s uch a s FM tuner, AM tun er,
or monophonic phono ca rtr idge, a r e plu gged into Channel I inp uts. Stereophonic sources, s uch as ste r eo
phono ca r t r idge , s te r eo ta pe heads, or FM, Mult ip l ex
(MX) adapt or, a r e plugged in as follows : left chan ne l
into channel l inputs; right channe l into channel 2 inputs.
Selling th e SELECTOR s wit ch to FM-AM an d the
MODE switch to STEREO or REVERSE take s care of
feeding two normally monophoni c channel 1 inputs
(F M tun er and AM tun er ) one to Channel I and th e
othe r to cha nne l 2 for FM-AM simul cast stereo.
I. PHONO: The PH. A Input jacks 1 and 2 and
th e PH. B input jacks I and 2 permit th e use of two
magn etic ca r t r idge s in your syste m. One ca r t r idge
can b e a ste r eo ty pe an d the othe r monophoni c or both
ca n be s t ereo.. One ca r t r idge ca n be in a turnta bl e,
an d th e other in a r ecord changer or an ine xpe nsi ve
phono for children's use. A monophoni c ca rtr idge is
plugg ed into th e chann e l l inp ut only.
When playi ng a monophoni c r ecord with a st e r eo
ca r tr idge , s et the MODE s wit ch to th e MONO 1-2 posi tion, spe cifi cally int ended fo r thi s purpos e. In th e
MONO 1- 2 position, the c han nel I and 2 inputs are
fu ll y blen ded inte rna lly, an d th e bl end is fed to both
amplifi ers . The purpose here is to ca nce l extraneou s
verti ca l noi s e component s in the ca r tridge out put.
When playing a monophoni c r ecord with a monophoni c ca r t r idge , s et th e MODE switch to MONO 1, th e
normal monophonic position at whic h the chan ne l 1
input is fed to both amplUiers.
~ ST- 84
Th e loa d pr e s ent ed to the cartridge by th e PHONO
A in put s is lOOK ohms. Th e load presente d to the ca rt r id ge by the P HONO Binputs is 47K ohms. Th e choi ce
of load i mp edan ce permit s acco moda tion of mos t popul ar ca r t r idges. Most popular car tridg e s, in cluding
a ll Shure a nd the Pi ck er in g 38 t A require 47K oh m
load. Th e Pi ck er in g 3a OA, ho wev er , r e quir es lOOK
oh m load.
If the Wea ther s C501- Dcart r idge is used, co nnect
a l aOK ohm r esistor in s e ries with it, fo ll owed by a
33K ohm re s i stor in shunt a cross the preamplifier
input. Plug into PHO NO A inputs . This net work avoids
overloading th e pr ea mplifi er whe n this cartr idge is
I
PAGE 5
Multiplex adaptor. Any a dapto r wi ll pr ovide a left
cha nne l output a nd a right chan ne l output. Th e left
channe l output is co nne cted to AUX. 1 a nd th e r ight
cha nne l outp ut to AUX. 2. The co nnecti ons d escribed
in 3 a bove sh all be made a lso.
6. TAPE : T he TAPE I and TAPE 2 input jacks
permit s th e conne ction of a tape ma chine co m ple t e with
pla yb a ck preamplifi ers . If th e ma chine provides s tereo
pla yba ck , co nnect th e upp er tra ck out put to TAPE 1,
an d the lo wer track outp ut to TAPE 2. If th e ma chine
is of the monophoni c typ e, co nnect th e out put to TAPE L
use d.
3-2. OUTPUT CONNE CTIONS
2. TAPE HEAD: Th e TAP E HEAD I & TAPE
HEAD 2 inp ut jacks permit th e connection of a t ape
deck ha vin g no pl ayba ck p r ea mplifier s to th e un it. T he
tap e head s hould be of the conventiona l high imped an ce ,
high outp ut ty pe normally s u pplied in de ck s wit hout
pl ayba ck elect ronics. If t he head i s of the stereo ty pe,
con nect th e upp er track out pu t to TAPE HEAD 1 and
the iower t r a ck output to T APE HEAD 2. If the head
is of th e mon ophonic type , con nect t he output to TAPE
HEAD L Th e load pre s ented to t he tape head by each
inp ut is 1 me goh m.
I. OUTP UTS TO TAPE RECORDER: Th e TAPE
O UT CH.l a nd CH.2 ja cks per mit fe eding th e ch annell
and channel 2 s ig na ls t o a ster eo tape r ecorder. With
monoph oni c sour c e co nnected to a channel l input, th e
TAPE OUT CR. I jack i s use d for f e eding out to a
monaur al tape recor de r . Low- capa cit y s hie lded audio
cables wit h RCA-typ e ph on o conn e cto r s a t the end ma y
be us e d in len gths up to 20 ft. to conne ct eac h jack to
the tape reco r der input s . Th e s ho r test pos sible lengths
s hou ld a lways be us ed. Note t hat any inputs chosen by
the SE LE CT OR switch fe ed out throug h th e se jacks .
Outp ut s a r e not af fec ted by ba lanc e, level, t one co nt ro ls
or fil ters.
3. MIC: Th e MIC 1 & MIC 2 input jacks pe rmit th e
co nnection of a single or s t ereo pa i r o f dynami c, cerami c, or cry s t a l m ic ropho nes to your un it . If you have
dyn a mi c mi cr oph on e s that can be connecte d fo r eithe r
low or high output i m pe dance , us e the hig h output i m ped an ce co nnection. For a ste r eo pa ir of mi croph on e s ,
con nect the left microphone to MIC 1 a nd the right
mi crop hon e to MIC 2. If a s ing le m icr oph on e is u s ed,
con nec t it t o MIC 1 o r :MIC 2 and us e MODE switch
setli ng MONO I or MONO 2 acco rdingly. Th e load
pre s ente d to the mi croph on e by each mi c input i s 1
megoh m.
2. SIGNAL CONNEC T IONS T O MAIN POWER
AMPLIFIERS: Th e PREAMP O UT CH. I an d CH.2 ja ck s
a r e e ach conne ct ed to the in put of a ba si c po we r a mpli fi e r . Th e two basic a mpli fi ers ma y be s eparate or
combined on one chassis. Low capacity s hie lde d aud io
cables with RCA- typ e pho no co nnecto rs at t he ends
s houl d be us ed in length s to 10 fe et norma ll y. If th e
cable capacity is as low as 25mmfd per foot, len gth s
up to 40 f eet ma y be use d if ne c e s s a r y. Howe ve r , the
s hortest pos sibl e cable length should a lways be us ed.
4. T UNE RS: For FM- AM s i mulcast tun er -s or
separate FM & AM tune rs, con nec t th e r egul a r F M
audio outpu t to the FM inpu t ja ck and t he AM output to
th e AM in pu t j a ck. Fo r FM Multiplex stereo tuners ,
including AM f a cilitie s or not, con nect th e left cha nne l
out put to the FM input jack and th e ri ght chan ne l outpu t
to the AM inpu t jack . If you have a non- s imulca s t
FM-AM tune r , such as the E ICO HFT- 92, connect th e
r egul ar au dio output to th e FM input. ja ck an d u s e the
MODE s witc h sett ing MONO 1 for mono tuner li s t ening. If th e AM in put jack i s us ed, the n the MONO 2
s etting is co r rect.
5. FM MULTIP LE X ADAP TOR: Th e AUX. I a nd
AUX. 2 inp ut ja ck s per mit the conne cti on of an FM
II1YAC
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3-3. PO WER CONNECT IONS
The po wer co r ds of the ba s ic power a mp li fie rs ,
th e turnt a bl e, a nd the tune r ma y be insert e d in th e
con ve nienc e outlet s p rovided on the r ear chass is apron.
The r ec eptacle marked 117 VAC is intende d fo r us e
pri ma r il y with a r ecord chang er or turntable and pr ovide s 117VAC r egardl es s of whethe r the po wer sw it ch of
the prea mp lifie r i s turned on or off in o r de r to p r ot e ct
th e r ecor d changer or tu r ntable m e ch a ni sm. The r e ce pta cle ma rked 117V AC SWIT CHED i s " li ve " or " de ad"
dep ending on whether th e pr eamplifi er power swit ch is
turne d on or off a nd i s inte nde d pri m arily for us e wit h
the basi c po wer amp lifiers . T he r e commend ed m eth od
is to plu g the line co r d of one ba si c power a mplif ier
rn rn
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AutZ •
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Figu r e 3-1. Re ar Panel Conn e ctions
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CHAUIEL I
~ ST - 84
PAGE 6
into the 117VAC SWITCHED r e c eptacle of th e ST 84 and
the line co rd of the othe r ba s ic power amplifier into ei the r convenience r e cepta cl e on th e fi rst powe r
a mplifie r . Tuners and othe r devices whi ch may be
turn ed on an d off wit h th e preampli fi e r power s wit ch
sh ould be plugged in to the re maini ng r e c epta cl es on th e
basic power a mplifiers.
3- 4. HUM ADJ USTMENT
1. AC LINE CORD ORIENTATION: ' Aft er checking th e preamplifier for proper ope ration make th e
following contr ol s ettings which ho ld throughout th e
proce s s of hum adjustment: SE LE CTOR swit ch at
PHONO B, MODE s witc h a t STEREO, th e BA LANCE
control a t 0, t he LE VE L cont ro l at 0, all swi t che s
down (off) , both BASS cont r ols at 0, both TREBLE co ntr ols a t - 5. Th e pre amplifier sh ould be conne ct ed to
the two basi c power a mplifiers whic h must in turn be
connec te d to the t wo sp eaker syste ms. The two sp eaker
sy st em must be in phase and placed near one anoth er
(or this adjustment . Conne ct the line cords of th e two
basi c powe r amplifi ers a s r e commended in POWER
CONNECT IONS ab ove . Plug the preamplifier lin e co r d
int o a Il7VAC wall outlet. Tou ch one end of a length
of hook- up wir e to th e pr eamp chassis and chec k for
a s pa rk when th e oth e r end i s tou ch ed t o a n unpainted
cha s s i s poin t on both po wer amplifi er s . If a spark
occu r s in e it he r case, r eve r se th e prong position of
the line cor d plug for that power amplifi er . Now place
your ear close to both louds peaker s a nd listen to the
hum le vel. Re vers e th e prong position of th e pre a mplifie r line co r d plu g in th e wall outlet an d listen
agai n. Choose th e pron g position giving the leas t hum.
With th e SELECTOR switch, s ele ct a parti cu lar
pie ce oC equipment, an d det ermin e th e inser ti on posi ti on oC its AC li ne co r d plug that r e s ult s in lea s t hum.
Repea t this Cor e ve ry piece of equip me nt us ed with
th e pr ea mplifie r .
2. HUM BALANCE: Separat e filamen t winding s
an d hu m - balance co ntrols ar e provided Cor th e two
cha nne ls , so that an opti mu m hum balan ce s ett ing can
be found for each cha nne l, rathe r than a co mpro mise
s etting for both cha nne ls . Conne ct th e phon ogr aph and
lea ve it s hut - off with th e ton e arm at r est. Set the
SELECTOR to th e PH. A o r P H. B position dep ending
on whi ch inputs are used. Set th e MODE switch at
MONO I, BALANCE at 0, LEVELat 10, BASS 1&2 at
0, TREBLE I & 2 at
(a mplifier tu rn ed on) . Set all
s lide sw itches at "off" (do wn). Adjust the cha nne l I
hu m -balance cont rol (R-57 ) with a sc r e wdr ive r until
the hu m hea r d fr om th e cha nne l 1 speaker is ata mini mum. No w se t th e MODE s witch at MONO 2 and adjust
the channel 2 hum -balan ce con trol (R- 58) until th e hum
heard Cram the cha nne l 2 s peaker is at a minimu m.
See fi gu re 5-3 for th e loc ations of R57 and R58.
°
3. GRO UNDING: The ca use of phonog r aph hu m
ma y be a met al pick-up a r m not grounded to the ca ble
I
shiel d (t ry a goo d s ing le ground connec tion to th e ca ble
sh ield fr om tu rnta ble fr ame, pi ck-up arm, and cartr idge ca s e ), dir ect hum pi ck-up by t he magn eti c ca r t ridge fr om the r e cord pl a yer mot or (try using a r ubber
ma t on th e tu r ntabl e to inc reas e th e s eparation of the
pi ck-up f r om th e moto r ), or pi ck-up Cra m a power
tran sfo rmer or other m agn etic fi eld in the vicinit y (try
movin g phonograph away from suspe ct ed s ource).
Che ck a l so that th e ph ono input cable shielding is
grounde d to th e amplifi er chassi s at one point only,
through th e s kir t of th e input connector where it plugs
into th e a mplifi er . Finally, try a goo d building g r ound,
su ch as a connection from a co ld wat er pipe t e rminated
und er a ny sc rew head on the r ear apr on or bot tom plate
of th e preamplifi er. Do not co nn e ct su ch a ground
wi re to othe r components in th e sys te m. H possible,
let eac h 'channe l be conn ected to the amplifier usin g a
s eparat e s hi elded cable to th e a mplif ie r input. It is
also desirable that th e ground leads on bo th cables not
be conne cted together a t a ny po int - not ev en at th e
car tr idg e . Howe ver, wit h s o me car t r idges , it will not
be possible to do thi s . In thi s ca se, just di sre gar d this
last instr uction.
3- 5. POWER AMP LEVE L ADJUSTMENT
To permit simultaneous acco mo da tion of ve ry low
output pi ck-ups and co m pa r a ti ve ly low s ensitivity power
amplifi ers, the ST84 is design ed with high gain. As a
consequen ce, it i s r equired tha t sho rted RCA -typ e
phon o plu gs be insert ed into a ll unused low input jacks.
Anoth er co ns eque nce of t he hi gh ga in, i s th at the
input le vel cont r ol s of the as soci a te d po wer a mplifie rs
mu s t be adjusted co r rectly. Adjustment is mad e by
ju st tur ning th e input level c ont r ols o n the powe r a mpli fie rs to mini mu m . Usi ng a ster eo pick-up co nne ct ed
nor ma ll y to you r preamp, pl ay a monoph on i c or ch est ra l
r e cor ding. Tu rn the ST 84 BALANCE cont rol to and
th e LE VE L cont r ol t o max imum. Set th e MODE s witch
to ST EREO and turn upthe inputleve lcontrols of power
a mp lifi er un ti l a vo lume as loud as you will eve r r e quire is r e a ch ed. Now yo u can adju s t th e LEV EL control s of th e preamp until th e desired listening le ve l is
obtained.
°
All E ICO s ingle and dua l pow er ampli fi ers ar e
now provided with input level contr ols . Som e po we r
amplifi ers of other man ufa cture do not ha ve level
cont ro ls . You ma y wish to provide l eve l co nt rols in
the latt er case if you ar e not using a low output pi ckup
an d low -effic ie ncy loudspeak ers. This may be don e by
mounting apai r of 500K ohm a ud io oot s in a small meta l
utili ty cabi net 4" x 4" x 2" (Bud Model CU8 83) an d c onnecti ng it between th e ST 84 prea mp out put s a nd th e
power a mplifier inputs. T he length of lead fr o m th e
pots to th e power amp lifie rs s hou ld be a s s mall as
possible. A sche mati c diagram of the connecti ons
fro m one preamp output to one po we r a mp lifi er inpu t
is shown be low.
~ ST- 84
TO ST- 84
OUTPUT
PAGE 7
TO
PWRAMP
I NPUT
,,
,
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500K OHM POTENTIOMETER
(VI EWED FROM SHAFT END)
Figure 3-2 . Input Level Con trol Conne ction
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TO POWER
AMP I
NOTE :DISCONNECT SHIELD
ON PLUG IF POWER AMPS
ARE ON SAME CHASSIS .
TO POWER
AMP 2
Figure 3- 3. Power Amp Connec tio n
mm:J
PAGE 8
I
ST- 84
SECT ION IV. OPERATION
as follows : LEVEL cont ro ls 1 & 2 at 0, BASS controls
1 & 2 a t 0, TREBLE co ntrols 1 & 2 at 0, LOUDNESS
compensation swit ch at OFF. Turn the syste m on by
s etting the POWER switch at ON. P lea s e not e that in
the instructions that fo llow, it is assume d that a st er eo
pickup and/or a st er eo tape head is being e mployed
in the sy st e m.
4-1. PRE LIMINARY
Be s ure all tubes are fi r mly s ea ted in their s ockets
and that the tube shields a re maki ng good contact with
their bas es. As initi al adjust ments , set these control s
4-2 . SELECTOR Swtt ch : Us ed to s elect any input or paIr of inputs a s follows :
POSITION
SOURCE
INP UTS
COMMENTS
TAPE/ AUX.
Pr e-am plifi ed tape
TAPE 1 & TAPE 2
MX/ AUX.
FM Mul tiplex Stereo
MX 1 and MX 2
FM-AM
FM tune r & AM tun er
FM &AM
TAPE HD.
Ster eo tape head in dec k
wit hout pr eamplifi er s
TAPE HD. 1 & TAPE
HD.2
PHONO A
Stereo mag . phone
cartridge
PH. A 1 & PH. A 2
Set MODE Sw at MONO 1-2 to
play mono rec or d
PHONO B
Ster eo mag. phono
ca rtridge
PH. B 1 & PH. B 2
Set MODE Swat MONO 1- 2 to
play mono r e cord
MIC
Micr ophones
MIC 1 & MIC 2
FM only with MODE sw, at
MONO I, AM on ly with MODE sw
at MONO 2.
4- 3. MODE Swit ch: Us ed to s elect mod e of ope r ation
POSITION
OPERATION
COMMENTS
CH. l plus CH.2 inpu ts blend ed out CH.l
speake r
For chec king left side of st e reo reproduction
BAL 2
CH.l plus CH.2 inputs ble nde d out CH.2
s peaker
For checking r ight s i de of st er eo reproduction
STEREO
CH.l inpu t out CH. 1 speake r
CH.2 input out CH. 2 speaker
Should normally giv e left s id e of pr ogram out
of left speaker , and r ight side of program out
of ri ght speaker .
REVERSE
CH. l input out CH.2 sp eaker
CH.2 input out CH.l speaker
Use if l eft s ide of program is co ming out of
r ight speake r when s et a t STEREO.
MONO 1
CH.l input out CH.l & 2 s peakers
Us e for mono li s tening when sour ce is pla yed
into CH.l inputs, except when playing mono
re cords . With stereo ca rtr idge.
MONO 2
CH.2 input out CH.l & CH.2 s peak ers
Use for mono listeni ng when sou rce is played
into CH.2 inputs, except when playing mono
re co rds . With st er eo ca rtr idge.
MONO 1- 2
CH.l plu s CH.2 inputs bl end ed out
CH. l & 2 speakers
Use d only when pla ying mono reco rd (with
ster eo cartr idge ).
BAL 1
~ ST- 841
4-4. LEVEL CONTROL
Use d to adjust th e listening level in both cha nne l s .
(Th e BALANCE cont rol is ad justed af t er s et ting the
LEVEL cont ro l. ) Substantial chang e s in LEVEL control s etting may r equire r e-setting the BALANCE
cont ro l. Adjust th e output level controls in stereo hi gh
level s our ce s (where present) to match th e sound level
obta ined on phono, if possible . If any of th e high l ev el
PAG E9
that clockwise r otation fr om th e mid-point (0 ) of eithe r
control in cr eases (boosts) bass r esponse ; th e minus
sign on th e left side indicates that co unter- clockwise
rotation from the mid-point decreas es (cuts ) bass
r espon s e. Th ere is no int eraction with th e TRE BLE
cont r ol. Start all adjustments with thi s co nt rol s et a t
th e mid-point (0), which is called th e "fl at " position
since bass respons e is neither cut nor boo sted at this
position.
sour ce s canno t provide high enough output t o m at ch
phono, s i mply s et th i s sour ce to maximum output .
4-8. TREBLE CONTROL CH. 1, TREBLE CONTROL
CH. 2 (CONCENTRIC)
4-5. BALANCE CONTROL
Use d to a chieve equal left and right side program
level s in s tereo. Eff e ctive in mono to ce nter th e ap par ent source bet we en the speakers. Neither channel
amplifier is favored (as to ga in ) at th e zero setting
(mid- rotati on).
As the contr ol is turned clo ckwise
fr om ze r o, th e cha nne l 2 (right) speak er is made louder
an d th e channe l l (left) speaker i s mad e softe r , while
th e ove r a ll l evel r emain s ab out th e same. As th e con trol is tu rned counter - clockwise from z ero, th e chan ne l
I (le ft) speaker i s made louder and th e channe l 2 (right)
s peake r is made s oft er, while the overall level r emains
about the s ame .
If audible balan c e is not achi eved at th e 0 s etting
of th e control, * the indication is th at th e s our ces fe edin g th e a mplifi e r ar e not equal. If th e s ource s have
th eir own level cont r ols , such as FM o r AM tuners or
Multiplex ada ptors, the n th ese level controls should be
set at equa l out put by successiv e ly setti ng the MODE
s wit ch at MONO 1 a nd MONO 2 while ad justing th e
s ource level con t r ols for equa l output in both positions.
Onc e the sour c e le vels have be en adjust ed, balance ca n
be a chieved by switc hing the MODE sele cto r f r o m BAL
1 and BAL 2 while a dju sting th e BALANCE con trol for
equal output fr om both channe l s at th e desired lev el.
If one s peake r is a little more effic ient than th e
othe r, or one power a mpli fi er i s more s ensitive th an
th e other, cut down the ga in at th e mor e eff icient s yst em
us ing th e level cont r ol on th at power amplifi er.
*Wit h the pow er amp le vel controls set as in 3- 5 and
th e LEVEL cont rol s et for a normal listening level .
4-6. LOUDNESS SLIDE SWITCH
A cha racte r i sti c of human hearing is that sensiti vity to bass tones diminishe s more rapidly, as th e
listening le vel i s lo wered, than s ensitivity to middle
and hi gh frequ en cy to ne s . Many people find the audible
lo ss of bass at low listening leve ls unsatisfying. Setting th e LO UDNESS slide sw itch to ON provides a co mpensating a mo unt of bass boos t a t low listening l evels.
Do not leave the LOUDNESS switch a t ON when li st en ing a t normal volu me , sinc e th e amount of bass bo ost
provid ed wi ll usually be exce ssiv e and unmusi cal.
Some people pr efer not to use loudness compensa ti on
at all, because it does not cor re spond to any natural
li st en ing condition at a li ve performance.
4-7 . BASS CONTROL CH. 1, BASS CONTROL CH. 2
(CONCENTRIC)
Th e plus sign on the right side of th e dial indi cates
Th e plus sign on th e right s id e of th e dialindi cates
that clockwise r otation from th e mid-point (0) of eithe r
control incr-eases (boo sts) tr eble r esponse ; the minus
sign indicat es that counter - cloc kwi se rot ation fr om
the mid-point decrease s (cuts) tr eble r espons e. Th ere
isno intera ction with th e BASS control. Start a ll adjustments with this control set at the mid-point (0), whi ch
is called th e "fl at" position since tr eble is neither cut
nor boosted at this position.
Th e a m pli fie r ON-OFF power switch is gan ged
with th e CH. 2 TREBLE cont ro l. Note the word " O F F "
on the panel just beyond full-counter-clockwise rotati on . Th e plain circle s ymbol preceding it indicates
that the power switch is ga nge d with th e CH. 2 cont ro l.
Turn the amplifier off by turnin g th e CH.2 TREBLE
control b eyond full counte r - clockwi se rotation until
th e power switch cli cks to OFF. Turn th e amplifier
on by turning th e CH.2 TREBLE cont rol cl ockwis e
(r om OFF and setti ng it a t th e mid-point (0) or so me
cus to mary setting of t he CH.2 TREBLE co nt rol you
may us e .
4-9. LO FILTER SLIDE SWITCH
Set to ON when it is de sired to cut low fr equency
r esponse below 100 cps becau s e of r umble in a phonogr a ph or ev en in broadcast program material. Phonograph rumble i s usually at about 29 cps and may we ll
not be dire ctly audibl e. Sometimes it can be at a much
low er fr equency, whic h i s definit el y not dire ctly audible.
Howev er, the eff ect of rumble can be heard eve n if th e
rumble it s elf i s not. It manif est s it s elf by using up
a mplifi e r po wer a t low fr equen ci e s a nd can even overload the a mpli fi er . If, at normal listening levels on
phonogr aph, s etting th e LO FILTER to ON definitely
r e sults i n "cleaner", le ss-distort ed sound, th e indicati on is that your phonograph s uffe r s from excessive
rumble. Whether it is wor th doin g any thing ab out it,
depends on th e installati on . If you have inexp ensi ve
s peake r syste ms th at do not produc e substantial undi storted sound belo w 80 cy cles, you may just as well
live with th e rumble and e li mina t e its bad effect s by
using the WW filter. If you have made a conside rable
in vestment in speakers, partly in order to obt ai n full,
und istorted response below 80 cycles, you may not
wan t to forego full ba ss r esponse. In the latt er case s ,
ha ve th e phonograph examined by a qualified servi ce
man to see if th e rumble is cause d by a defect that
can be r e me die d.
4-10. HI FILTER SLIDE SWITCH
Set to ON when it is desired to cut hi gh frequ ency
PAG E IO
~ ST -84
r es pons e above 5000 cps . Useful for minimi zing e xtra neou s noi s e when list enin g to narrow range AM
broadcasting, for list ening to noi sy or worn re cords,
and for r educi ng the annoyance of exces s ive distortion
from any sourc e.
4-11. TAPE MONITOR SUDE SWITCH
Useful with co mple te tape machin e s (including
re co rd and playback e lec tronic s ) that provi de off - thetape monitor ing faciliti es whil e re cording. In this
s itua tio n, s etting th e TAPE MONITOR sUde s witch to
ON permits you to hear the program being r e cord ed
directly fr om the tape.
I
4-17. USTENING TO A STEREOPHONIC SOURCE
CONNE CT E D TO TAPE I AND 2, AUX I AND
2, AM AND FM
Set th e SELECTOR to TAPE, MX!AUX, or FM-AM
r espe ctively. Set th e MODE swi t ch at STEREO or
REVERSE.
4-18. MAKING RECORDINGS
Tape r e cordings may be made by connec ting the
r e corder to th e T AP E OUTPUT jacks. P lease note
that r ec ordings cannot be made on tape de cks unless
those de cks are equipped with the e le ctro nic s requir ed
for re cord ing.
4-1 2. TAPE EQUA LI ZAT ION SLIDE SWIT CH
Adjust s the equa li za ti on at the TAPE HD. pos ition
of the SE LECT OR s wit ch a c co r ding to th e NARTB
standard for the 7- 1/2 (and IS ) ips tape s peeds an d
3- 3/ 4 ips tape speeds.
4-1 3. USTE NING TO PHO NOGRAPH
Set th e SELE CTOR switch t o PHONO (A or B) if
you have a magneti c cartr idge, or a ce ra mic /c rystal
cartr idge with adaptor s interpos ed betwe en the ca rt ri dg e ou tputs and th e MAG. PHONO I a nd 2 inputs.
(The RIAA equa lizatton provid ed a tth e PHONO position
is no w the int ernational standard in the r e cording in dustry for both monophonic and stereophoni c re cords
and is also a ver y good co mpro mise for the most i mportant of the older monophoni c r e cord ing characte r isuc s . ) Set the SELECTOR s wit ch t o th e appropriate
AUX if you ar e us ing a st er eo phonic ce ra mic/cry st al
ca rtr idge conne cted to the AUX or TAP E pair of inputs .
To play a s te reophonic re cor d, s et the MODE switch
to ST EREO or REVERSE for ste reo listening. To play
a monophoni c rec ord, the proc edure is exac tly the
sa me, only the MODE switch r emains s et at the MONO
1.2 pos ttton, pr oviding th e identical signalin both channel s with mixing of the inputs for vertica l rumble
cancellatton.
4-14. LISTENING TO TAPE DECK (di re ct con nection
to tap e hea d)
Set t he SELECTOR to TAPE . NARTBtape equa li - ·
za tion is provided in both channe ls for the tape s pee d
sel e ct ed with ihe TA PE switch on th e fr ont pan el.
One position is for 7-1 /2 ips tapes and the othe r for
3-3/ 4 ips tapes. The s e equali zations are the indus try
standa rd for pre-r e cor ded s te reophonic and monophonic tapes.
4-1 5. LIST ENING TO A MONOPHO NIC SOURCE CONNEC TE D TO TAPE I , AUX I, OR TO MONOPHONIC FM BROADCAST
Set th e SE LE CTOR to TAPE, MX! AUXor FM-AM
r e spe cti vely a nd the MODE s witch to MONO I.
4-1 6. LISTENING TO A MONOPHONIC SOURCE CONNE CT E D TO TAPE 2, AUX 2, OR TO AM
Set th e SE LECT OR to TAPE, MX!AUX, o r FM-AM
r e spe cti vel y and th e MODE switch to MONO 2.
SECTION V. MAINTENANCE
5- 1. GENERAL
Your prea mplif i er shoul d require little . s er vi ce
except fo r nor mal tube r eplacem ent. We re commend
no substitutions for the tube type s used in thi s amplifi er except as s tated. All the tube types used ar e
distributed natio nally , but r epl acem ents can be obtained
dir e ctly fr om EICO if de sired.
To faci litate s ervt ctng.remedtaj and tr ouble -shooting procedur es have be en provided in the TROUBLE
SHOOTING CHART tha t follo ws. VO LTAGE and RESISTANCE CHARTS are a lso provi ded as a n ai d to
locating defe cti ve co mponents .
5- 2. TROUBLE-SHOOTING PROCEDURES
Set the SELECTOR swit ch at PHONO A o r B,
whic hev e r is appro priat e, and the MODE s witch at
ST EREO o r REVERSE . P la y a known hi gh qua li ty s te r eo
re cording on the phonograph. If ther e is no output to
one or both s peake rs, or if the output is low or audibly
distort ed, pro ceed to the checks for those sy mpto ms .
If the re i s e xce s s ive hum in the output, dis conne ct the
appropri ate phono input cable fro m the preamp lifi er
and shor t the phono input jac k at the chas s i s. If the
hum disappears, the trouble is not in the amplifi er but
in the phonograph or in the connection to the amplifier.
In each ca se, chec k for the tr ouble in the preamplifi er
channel which seems defe ctive. If both channel s are
def e ctiv e, check the power suppl y..
The caus e of phonograph hum may be a metal pickup arm or motor not gro unded to the preamplifier
chas s i s (run these ground leads dir ectly to the pre amplifier chas s is , not to the oute r bra id conductors
of th e ph ono input cable s ), di r ect hum pi ck-up by the
magneti c cartr idge fro m the r ecord playe r motor (try
using a rubber mat on the turntable to incr ease the
s eparation of the pic k-u p fr o m the motor ), or pick - up
from a powe r transfor me r or other magentic field in
the vi ci nity (try moving phonogr aph away fro m suspe ct ed sour c e). Ch e ck a ls o that th e phon o input ca ble
s hie lding i s grounded to the a mplif i er chass is at one
poi nt only, through the skirt of the input co nne ctor
wher e it plugs into the amplifier . Finally, tr y a goo d
building ground s uch as a co nnection from a co ld wat er
pipe terminated under speaker terminal "G" on the
~ ST- 84
am plifi er . Do not conne ct such a ground wir e to othe r
co mponents in the s yst em. If possible , le t eac h channe l be co nnec te d to the amplifie r us ing a s eparate
shi elded cable to the amplifier Input , It is also desirabl e that the ground leads on both cabl es not be co nnected together at any point - not even at the car tr idge .
However J with som e car tr idge s , it will not be possible
to do this. In this case, just disr egar d thi s last in struction.
Excessive hum on othe r inputs may be checked in
a s imilar manner . Dis conne ct the input cable in que stion
and short the parti cular input jack to the chas s is. If
the hum disappears, the trouble i s exte rnal to the pre amplifier . Note that on all inputs , the braid of the input
cable s hould co nnec t to the preamplifi er only through
the skirt of the input connector. The caus e and remedi e s
for the following s ymptoms ar e the n based on the as sumption that che cks made in the manner des c ribed
above have eli minate d the pos sibility of the trouble
being exte r nal to the preamplifier .
IT the trouble is no output or low output, chec k AC
si gnal volt ages and DC ope rati ng vo ltage s starting at
the input and wor k st ep-by - st ep toward the output in
eac h amplifi er. Set the LEVEL contro ls to maximum
I
PAGE 11
(10), th e BASS and TREBLE cont ro ls to th e ir mi d-point s
(0), the SELECTOR switch to PHONO an d the MODE
s wit ch to ST EREO or REVERSE. Us e a 1000 cycl e
s inewave s ignal, such as supplied by the EICO 377 Sine
& Squar e Wave Audio Gene rator. In additi on, us e a
precision 100: 1 att enuator to pe rm it obtaining a le vel
of 0.0032 volt f ed into the a ppropr iate PHONO A o r B
input fr om an audio gene rat or output of 0. 32 volts,
which can eas ily be measu red on the lowest AC volts
range of your VTVM (also i mproves s ignal to hum from
ge ne r a to r ). Us e a ht gh input t mpedanc e VTVM for a ll
AC s ignal voltage measure ments; a VTVM or 20, 000
ohm/V YOM for DC volts measur e ments .
IT the trouble i s an e xces s ive ly di stor ted output,
try tube r ep lacem ent, s ignal tra cing, or proc eed dir e ctly
to voltag e and resistanc e mea su rem ents.
5- 3. TRANSFORMER TEMPERATURE
The transformer used in thi s unit run at a temp eratur e less than 1950F despite the fa ct that t he safety
limit t s a t a mu ch higher 22 10F. Alt hou gh 1950 is cool
for a transformer, it is ve ry hot to the touch. Tr ansformers which seem too hot when touched with the
hand, are usually good and ar e ac tuall y not ove rheating.
Fi g. 5-1. TROUBLE SHOOTING CHART
SYMPTOM
Pr eamplifie r caus es power line
fus e to blow.
CAUSE
REMEDY
Line co rd, J Ig, J20, primary or high
voltage s e co ndary Windings of Tl incor rectly wired.
Repair
Pri./h. v , s e c. windings of T1 s horte d.
Repla c e
Open lead fr om 6V (gree n leads)
winding of T I.
6V windin g (gre en lea ds ) of Tl open.
Re pair
Open lea d fr om 6V (brown leads )
wind in g of TI.
6V windi ng (br own lead s ) of Tl o pen.
Repai r
a) No voltage
Defe cti ve V6
C31A shor ted inter nally or exte rna lly.
Conne ction to ce nte r -t ap of high voltage
winding of Tl is open.
Repl a c e
Re pla c e (or r epair )
Re pair
b) Low voltage
C3 1A O.K. but C31B or C31C short ed .
C31A open or no co nnec tion
Excess iv e cur re nt dra in in amplif ier
Repl a ce
Repla ce (or r epair)
Repair
c ) High voltage
Tube s VI- V5 defe ctive or ove r - bia sed
and not drawing normal cur re nt.
Open R59, R60, R61 or R62
Rep a ir (or r epla c e)
Short ed ,pot to chas s is thro ugh mounting
s cr ews
Mount s cre w head for
pot bel ow chas s i s and
not on top s urface of
chass is .
VI, V3, V5, V6 an d pil ot tube
filame nt not li t.
V2, V4 tube filaments not lit.
Replac e
Repl ab e
DC voltage at V6 cal hode (pin 7)
is inco rrect as s pe ci fi ed below.
Fil am ents not at DC potenti al hum
Repla ce
mmJ
PAGE 12
ST-84
I
Fig. 5-2 . VOLTAGE & RESISTANCE CHART
T UBE
VI
(ECC 83/ 12AX'7 )
V2
(ECC83/ 12AX7)
V3,V4
(both EC C83 /
12AX7)
V5
(ECC83/ 12AX'7)
V6
6X4
PIN
*
OPERATING VOLTS
(DC UNLES S NOTED)
SIGNAL VOLTS
(Ike) at 2V O UT
OHMS
(UNIT DISCONNECTE D
FRO M P OWER)
I
2
3
4&5
6
7
8
9
. 38
113
. 025
0
.014
0. 83
rn. (12VDC; 6VAC to pin 9)
. 025
41
. 0032
0
.0038
0. 5
51K
1. 5M
1150
I
2
3
4&5
6
7
8
9
' . 082
50
.026
0
0
1.83
fil. (12VDC ; 6VAC to pin 9)
. 026
78
0
0
0.45
51K
1.5M
1150
I
2
3
4&5
6
7
8
9
3.2
0.47
0.32
ru, (12VDC; 6VAC t o pin 9)
0.47
140
0. 19
0
0. 19
1. 15
iiI.
IIIK
470K
2. 2K
I
2
3
4&5
6
7
8
9
2
140
0. 13
0.4
0.050
I. 25
ru, (12VDC ; 6VAC to pin 9)
2
140
0. 13
0.4
0.050
1. 25
iiI.
44K
260K
IK
I
2
3&4
5
6
7
265 VAC'
341K
113K
2300
ru,
355K
113K
2300
fil.
180
0
1.5
ru,
(12VDC; 6VAC betwe en pins 3 & 4)
265 VAC'
345
23 1K
125K
2.2K
44K
260K
IK
400 - 90 0
-
-
400 -900
over 30K
• = 60 cy cles
All r e s istance measurem ents, except fro m pin 7 of V6 (6X4 re ctifier) are mad e with pin 7 of V6
grounded. All voltage and r esistance measur em ents ar e meas ur ed to chas si s with controls s et as
fo llows: SELECTOR Swit ch to P HONO A, MODE swi tc h to MONO I , BALANCE contr ol at 0, LEVEL
cont ro l a t 10, BASS I & 2 and TREB LE I & 2 co nt ro ls a ll at 0, a ll slide switch es down to off position.
For voltage measurem ents as they appear in this chart, fe ed 0.0032 volts (3.2mv) Ike signal into the
PHONO A l input only , sh orting out the PHONO A2 input. Voltage measurement s are mad e wit h a VTVM.
Oper ating lin e voltag e at which voltage measurem ents are made is 117VAC, 60 cps . NOTE: ALL VOLTAGE & RESISTANCE VALUES MAY NORMALLY BE ± 20%.
~ ST - 84
12AX7
12AX7
V5
v3
1
PWR TRANS
TI
V6
6X4
V4
-~
I ZA X7
R5 8
CHAN.2
HUM SAL
...... , ,
R57
CHAN.I
HUM SAL
Figur e 5- 3. Tube Layout (Top Chassi s Vi ew)
12AX 7
HUM SAL
CHAN.I
12AX7
J2AX 7
VI
R57
V3
V5
C 31
•
V2
12AX7
R58
CHAN. 2
V4
V6
12AX 7
6X4
HUM SA L
Fig-ure 5- 4. Bott om Chass is Vie w
FI
IA .FUSE
_
PAGE 14
mm.J
SEC TION VI. EI CO'S SERVICE POUCY
If you are expe r ie ncing troubl e that you cannot
diagnose yours elf, you a re invit ed to a vail yourseU of
th e EICO Se r vi ce Consultation Depa r t ment. The con sultant handling your inqui ry will make eve ry effor t to
diagnos e the ca sue of you r parti cular difficulty based
on th e informati on that ~ pr ovi de. Plea se be as
thorough as pos sib le. In clude th e following infor mati on
about your unit:
a) Hav e you made a thorough check of th e wiring,
checking also for cold so lder joints, or acci dental shorting between parts, or to chassis?
(Check to see whet he r a ba r e wire or lead ext ends fa r enough to be s horted whe n th e bottom
plat e is put on).
b) Have you checked that th e proper tube or trans i sto r is in each socket, and a lso making pr oper
contact in the s ocket ? Ar e all sh ields firmly
in pl ace?
c ) Does th e t r oub le occ ur at one time or one
operati ng sit uation, but not at another time or
oper ati ng s ituation? Be as s pecifi c as possibl e
in this r espect.
d) If the unit is of the t ype that invol ves alignm ent
or cali br ati on, be as sp ec ific as possible as
to wha t you ha ve done or not don e wit h regard
to these r equirements . If th e unit incorpora tes
tu ned cir cuit s stat ed to be facto ry pr e-aligned,
did you cha nge any s ettings ? If so, what align m ent proced ur e did you us e ?
e ) Ha ve you obse rved an y pecu larityabout a part ?
If a pa rt appears cha r red or oth er wise damaged
by e xces s ive h ea t, pl ease s a y so. If you th ink
you have damaged a pa rti cular part in th e
as s e mbly or wiring, please say so. In co njunction with th e s ymptoms, th e consu lt ant ma y
be ab le to det er mi ne wheth er such a part is
lik e ly to be defecti ve.
/) Ha ve you gone through an y trou ble-shooting
pr ocedu r e tha t may be provid ed ? If your manual
includes a table of conta cts made at each switch
positi on, ha ve you chec ked out th e swit ch es
a cco r dingly (if the t rouble is such that doing
thi s would be appropri at e )? Hav e you been able
to make checks of th e ope r a ti ng voltages and /or
r es is tan ce s , if th i s is a ppr opr ia te , and your
man ua l provides a t able of voltages an d resist a nces ? What a r e the r esults of these chec ks ?
Als o, ha ve you taken an y ot her troubl e -shooting
approache s ? What hav e been th e r esults ?
g) If this is high fidelity eq uipme nt, please s ta te
th e typ e (magnetic, ce r a mic , cr ys ta l ) of phono
car t r idge you ar e using an d/or th e make and
mode l numbe r . Sta te th e mak e and model of
your r ecord changer, or turntable a nd ton e a r m.
Ar e the s peakers in th e same cabine t with
you r e lect r oni c equipme nt? 'If so, des cribe the
cabinet and th e pl ace me nt of the components .
Plea se s tate th e make and model of your sp eaker s .
ST-84
I
In addition, li st a ny code numbers in r ed und er th e
words INST RUCT ION MANUAL on the cove r of th e
book pr ovid ed with your unit. If th e r e a re no r ed code
numbe r s , st at e this specifically. If th e unit bears a
s erial numb er, i t Is es senti a l th at you include this also.
PARTS REPLACEMENT
If it appea rs that a co mponen t is defective, and
you desir e a r ep lace me ntfro m EICO, address your cor r esponden ce to our Customer Service Department.
If you a re claimi ng the r ight to a no- charge r epl ace ment unde r the te r ms and conditi ons of th e war ranty, it is r equi r ed th at you s ha ll ha ve s e nt in the
r egi s tr a ti on card within 10 days of th e da te of pur chas e,
and that you s en d back th e def ective part tr an spo r ta ti on
prepaid. EICO will make th e necessary r eplacement
a t no cha rge for parts eli gib le und er th e -t e r m s and
conditions of th e war r anty. In r et ur ning tube s , pack
th em ver y ca refully to av oid br eak ag e in shipment.
Br oken tubes will not be r eplaced. P lea s e r ead th e
war ranty on th e subj ect of pa r ts eligible for repla ceme nt.
Furth er info r ma tion r equired on a pa r t r etur ned
to the factor y for a no- charge r ep la ce me nt under the
terms an d conditi ons of the war ranty i s a s follows :
a ) Model numb er an d s e ri al numb er, if. a ny, of
unit. Als o any cod e numbers in r ed under th e
words INSTRUCTION MANUAL on the cove r of
th e book s upplied wit h the uni t.
b) Stock numbe r and description of part as gi ve n
on th e parts Its t. If the part is not li sted (of
itself) in th e pa rts list, it means that th e part
is int egral with a sub- assembly. If th e subassembly is not s ealed, and the def ective part
is definite ly identified a nd ea s ily replaceable
(not more than two connec tions ), you ma y r eques t r eplace ment for th e particular par t. If
th e sub -asse mbly i s s eal ed, or if the def ecti ve
pa r t is not defi nite ly id entifi ed or is not eas ily
r ep lacea ble (more tha n two connections ), then
r emove the s ub -asse mbly a nd r etur n it t o EICO
(less any tube s ) for r epa ir or replace me nt, if
your uni t is in wa r rant ee. If your unit is out
of war rant ee, you ar e gen erall y ad vi s ed to
or de r a r eplac e me nt sub- as s embly.
c) De s c ribe as co mpletely a s pos sible th e na ture
of th e def ect, or your r eason for r equir ing
r eplace ment.
FACTOR Y REPAIR SE RVICE
EI CO maintains a Fact or y Re pa ir Service Depa r tment for in - wa r r anty or out -of- wa r r an ty r epair of
EICO equi pme nt. It is intended to ser ve th os e custo mers
who ar e not ad equate ly fa mi liar with ele ct r oni cs to
mak e use of th e EICO Ser vi ce Consultation faci li ties , or
whose diffi cnlfies ca nnot be s olv ed by cor r es ponde nce.
For a ll out - of -warranty units, th er e is a minimum
la bo r and handling fee. For th e Model ST - 84, thi s fee
is $ 10.00. Charges for components r eplaced a r e additi onal to t he minimum fe e.
For in -warranty completed ki t uni ts , ther e i s a
mini mu m labor a nd handling fee. For th e Model ST -84,
thi s fee i s $10. 00. Th ere i s no cha rge for a r epla ced
defective par t provided that the terms a nd co nditions
of th e war ranty for no cha rge r eplacement ar e not
vio laied in th e judgement of EICO.
For in- wa r r ant y factor y-wir ed uni ts, th ere is no
labor an d hand lin g fee if the unit co mpli es with th e
te r ms an d co nditions of the warr an t y in the judge m en t
of EICO. Howev er, if the t er ms an d conditi ons of th e
war r an ty ar e vi olat ed, then t her e will be cha rged to
custome r a minimum labor and ha ndli ng fee plus th e
co s t of parts r epla ced.
In all cases , th e unit mus t be s ent to th e factory
transportati on prepaid, and the unit will be r etur ned
to th e cus to me r t ransport ati on co llect.
Th e s ervices r e nde red for the minimum labor an d
han dling fee are th e cor re ction of any minor wir ing
e r r or s (not exte nsive cor rections or r e- wir ing), the
lab or invol ved in r eplacing defecti ve parts, and any
adjus t me nts , a li gn me nt, or cali bration pr o cedures th a t
would normally be performed on a fa ct ory- Wired unit.
Units not wired accor ding to instructions, or modified
in an y wa y, or showing e vide nc e of th e use of acid co r e
s old er, wi ll not be s ervi ced a nd wi ll be r eturned to th e
cus tomer for thwith.
Units r equ ir ing extensi ve co r r ections or r e- wiring
will in cu r an additional labor charge which will be s e t
by EICO. Th e cus to me r wi ll be inf ormed of this s it u ation an d written authorization from th e custo m er will
be r equir ed befor e th e work i s done.
Pleas e not e: min i mum labor an d handl ing fees are
subject to r evision at a ny time.
LOCAL REPAIR FACILITIES
Out - of-warranty repa ir work ma y al so be performed by authori zed ser vice sta ti on s as we ll as th e
EICO fa ct or y. A li st of authorized s er vice stations is
pr-ovide d wit h th is man ua l. Th e r ost er of stations ma y
cha nge fr om time to ti me, an d if cons ide r a ble time ha s
e la p s ed si nc e you purchased your unit, you ar e advis ed
to co ntactthe s tation you choose before s ending the unit
to them fo r r epai r . Us e of a local s e r vi ce station will
oft en r esu lt in fa s te r s ervice, a nd, usually, lowe r
t ransportation cos ts.
It is necessary that you comply with the Shipping
Instructions th at follow when s ending in a unit for
s e rvi ce.
SHIP P ING INST RUCT IONS
You a re s t rong ly advi s ed to r etain th e or igina l
shipping ca r to n a nd inse r ts in th e case th a t r e-shipmen t
~ ST -84
I
PAGE 15
is requir ed for s er vi ce or an y othe r purpose. The carton .~t:~8~;~8~::8~I:S:::S~::S~t;8~:~-="~t~s;l:at;8:::S;t:8:1is:.
(11• • •• , . _. • • ' . • • • .- . • • • • , - ,. •• -[I]
ma y be collaps ed, for s to r a ge in as small a space as ,..;.
~
THE E ICO WARRANTY ~
.....
possible . In very many ca s es, th e same carton is used 'j'
~
~
for kit and fa ctory- wir e d units s o that the kit carton
The E lectronic Ins t r u me nt Company, Inc., her e- :.,:
will se rve for r e-shipment of the completed kit.
(I) aft er r efer r ed to as EICO, warrants that, for a period (I)
:.;.: of 90 days fr om the date of purchase, any E ICO kit will ~
(:I:
To submit a unit for service, either t o th e fa ctory J!l4 be free of defects in par t s, and that an y E ICO factor y- ~L
or an author ized ser vice s ta ti on, * fill out co mple te ly ~v, wir ed unit wi ll be fr ee of defects in parts and work - fr'
the Ser vi ce Work Order form provided wit h the manual. ~~4 manahip. For an E ICO kit, E ICO I sobligation is li mit e d ~~.l
Pack the unit ve ry ca r efull y, pref erably in th e or igina l lil' to those parts whi ch ar e returned transportation pre- lilt
s hipping ca rton with th e original inser t s .
:.;.~ paid to the factor y without fu r th er da mage , and in the :.,:
(I) judgement of E ICO ar e either originally defective or (I)
If thi s is not possible, us e a strong ove r s ize c ar ton, ;tZt: have be co me defe ctive in nor mal us e. For an E ICO
preferably wood, a l.lowin g at le a s t 3 inches of r e s ilient
factory -wired unit , E ICO' s obli gati on is limited to ~mt
packin g mat erial su ch as shredded paper or exce ls io r , -r)' thos e part s, s ec ti ons , or the enti re unit which is re - ~~)'
to be inserted between all sides of the unit and the .~t turn ed t ransportation prepaid to the factory without ~4
car-t on , Seal th e ca r ton with strong gummed paper tape
furth er damag e, and in th e judgement of EICO are e it he r '(i)'
or strong twin e, or both. Include th e Servi ce Work :~ originally def e ctive or ha ve b ec ome defective in norma l :-:*:
Order in th e carton and in additi on, attach a tag to th e ro UH.
00
instrument on which is pri nted your name and address
Th e warrant y does not app ly to any parts da mag ed
and brief referen ce to the t r ouble exper ience d. Affix
"FRAGILE " or "HANDLE WITH CARE " la be ls to at ~: in the cou rse of handling, ass embling, or wiring by the :ru:
least four sides of th e ca r to n, or print th ese words ~m. custo mer J or damaged due to abnormal usage or in
lar ge and cl ear with a bright co lor crayon. Ship by li)' vio lati on of inst ructions or r easonable practice, or lilt
W fur th er damaged to a consequential degr ee in r eturn .~
prepaid Railway E xpress or parcel post to:
ship ment. Furthermore, th e for egoing warranty is ~ ..
Electronic Ins t r u me nt Co., Inc .
'''
('I'' made only to the or ig ina l cus to me r , and is and shall ~(Tl'
be in li eu of all ot he r warranti es, whether expre s s ed
33-00 Nor ther n Blvd"
~: or implied, and of a ll ot her ob li gations or liabi litie s :00:
Lon g Is land City 1, Ne w York
Att ention: Servic e Depa r t ment
~lI.4 on the part of EICO, an d in no event shall EICO be li able W
!J: for any anticipat ed profits, consequential damage s,
Incl ude you r name and address on the out s ide of 'r~I~' los s of tim e, or ot her losses incur r e d by the cus to me r '(-I','
the carton. Return shipment will be made tr ans po r ta - ~ ;J in connection with th e pur chase or op eration of E ICO
W products or components the r eof.
W
ti on charge s co llect. Note that a carri er cannot be lilt
lilt
held liable for damages in tr ansit, if packing, IN HIS W
~
OPINION, is in suffici ent.
lilt
The regi stration card, which acc ompani es ea ch
'"4 E ICO kit or factor y-wired unit , mu st be filled in a nd '44
*Autho r ized s er vi c e stations a r e for out- of -warrant y
r et urned to the company wit hin 10 day s aft er th e dat e
u nit s only, un less th e s ta ti on is sp e cifically noted on :0;.: of purchase. This war rant y appli es only to registered :->:
.f!),
th e List of Authorized Servic e Stations to be auth ori zed J!l. units,
fo r othe r work.
:~:
I
J!l
til'
:*:
til'
:m
m:
,,'J!l
·1
m
J..
m:
lit
liJ
liJ
. 'X
'S':'S':'S:l'S';'=';'S'X
'S':I=';'=';'S'X
'S';'-: ,~IS,:,SIIil
.:;<B-J
PAGE 16
ST - 84
I
SE CTION VII. PARTS LIST
SYM.#
STOCK*
AM'T.
C1, 2, 3, 4, 5, 6
C7,8
C9, 10
CII, 12
C 13, 14
C1 5, 16
C17 , 18
C 19, 20
C21, 22
C23, 24
C2 5, 26
C27 , 28
C29, 30
C3 1
C32
C33
C3 4
FI
22 5 17
22538
22 536
22 522
22520
22580
22 53 4
22517
20039
22 532
20057
22563
20039
24020
230 16
23028
20043
9 1002
92000
50020
6
2
2
2
2
2
2
2
2
2
2
2
2
I
I
I
I
I
I
2
capacito r , di s c, . 025mf d (25K or 25,000mmf) GMV
capacito r , di s c, 400mmf, 10%
capacitor, di s c, 25mmf, 10%
capac ito r , di s c, 330mmf , 10%
capacitor, di s c, .00 12mfd (1.2K or 1200mmf ), 10%
capac ito r, di s c, .2mfd, lOV
capacitor, di s c, 68mmf, 10%
capac itor, dis c, . 025mfd (25K or 2 5,000mmf) GMV
ca pacitor , molded , .1 mfd, 400V, 10%
capaci tor, di s c, .0015mf d (1. 5K or 1500mmf ), 10%
capac ito r , mo ld ed, . 47mf d, 200V
capacitor, di s c, .01mfd (10K or 10, 000m mf) 25V, 10%
capacitor , mo lded, . 1I1]fd, 400V, 10%
capac itor, elec., 2 x 20mfd, 400V + 2 x 40mfd, 350V
ca pac ito r , elec., 30mfd, 400V
capac itor, elec. , 10mfd, 150V
capa ci tor , mold ed , . 03mfd, 600V
fu s e, I Amp
pilot li ght bulb, #47
ja ck, input, quadr upl e
500 18
2
ja ck, input, tr ip le
500 11
500 16
2975 1
29753
10428
10410
11526
10424
10407
10455
11512
11533
1152 3
11520
10435
1040 8
11532
10421
18068
18069
104 13
10417
10423
10431
10426
10410
18071
18096
10426
19016
10449
10400
10444
1045 1
10410
60 100
60 101
620 12
62014
620 12
2
2
2
I
2
2
4
2
2
2
2
2
2
2
4
2
2
2
I
I
2
2
4
2
2
2
I
I
2
2
2
I
I
I
I
I
I
2
I
2
I
I
2
3
jack, input , dual
AC receptacle
print ed ci rcuit, 7 lead s
pr int ed cir cuit, 5 lead s
r e si stor, 47K, 1/2W, 10% (ye llow, vio le t,orange ,silver)
r es i s tor , l OOK, 1/2W, 10% (brown. black.ye llow.eflver -)
r e s i stor,200K, 1/2W, 5% (r ed,b la ck, yell ow,gold)
r es i s tor, 22K, 1/2 W, 10% (red,red,o range,silver)
r es i s tor, 1M, 1/ 2W, 10% (brown.bla ck.gr ee n.sftve r ]
r esisto r , L 5M, 1/2W, 10% (brown. gr-een. gr-een . atlver-)
r es i s tor, 2400 , 1/2W, 5% (r ed ,yellow,red ,gold)
r e si stor, 1200, 1/2 W, 5% (brown.r-ed .r-ed .gold)
r es i stor, 68K, 1/2W, 5% (blue,gr ay ,o range, go ld)
r es ist or, 40K, 1/2W, 5% (yellow,b lack,orange,go ld)
resistor , 150K, 1/2 W, 10% (brown,g reen ,y e llow,silver)
r esi s tor, 680K, 1/2W, 10% (b lue,grey,yello w,silver)
resistor , 4M, 1/2W, 5% (ye llow,b lack,gree n,go ld)
r esi stor, 6800 oh m, 1/2 W, 10% (blue,gray,red, s il ver )
pot en ti om e ter, 7 50K, dual
pote ntiometer, 250K, dua l
r e s i st or, 2.71(, 1/2W, 10% (r ed , vio let, red, s ilver ) )
r e si s tor,220K, l / ZW, 10% (r ed,red ,yello w,silver )
r esi stor, 2200 oh m, i/ zw, 10% (red, red,red,s ilver)
r e s istor, 470K, l / ZW, 10% (yellow,violet, yell ow, si lver )
r es i s tor , 33K, l / ZW, 10% (orange,or ange,orange,silver)
resistor, l OOK, 1/Zw, 10% (br -own.bla ck .yel low. ai lver )
poten ti om et er, 1M, concentric
pot enti o met er, 500K, concentric , w/S PST sw itch and cover
r e s istor, 33K, 1/2W, 10% (oran gc, oran ge,or an ge, s il ver )
potenti ometer , 100 ohm, WW
r es i st or, 5600 oh m, 1/ 2W, 10% (gr een. b lue .z-ed.ailve r )
res istor, 10K, i/ zw, 10% (brown. black.o r ange.st tver ]
r es i s tor, 1Z0K, l /ZW, 10% (br own. r-ed.yellow.a flver-)
r esistor, 27K, i/ zw, 10% (r ed , viol et,or an ge, s il ver )
r esi st or, l OOK, l /Z W, 10% (br-own.black.yel low. at lve r -)
switch, ro ta ry, 4 section
sw it ch, rotary, 1 section
switch, slide, DPDT
switch, slide, 4P DT
switch, s li de, DPDT
switch, SPS T mount ed on R53 - 54
tr ansfo rmer, power
terminal s tr ip , 1 pos t left
te r- mina l s t rip, 1 post right
II
J1 ,2, 3, 4;
J 5, 6,7, 8
J 9, 10, 11; 12,
J1 3, 14
J1 5, 16; 17, 18
J1 9, 20
P C1,2
PC3
RI , 2
R3, 4
R5,6 J 7 , 8
R9, 10
Rl1, 12
R1 3,14
R15,1 6
R17, 18
R 19,20
R21, 22
R23,24,25, 26
R27,28
R29,30
R31, 32
R33-3 4
R35- 36
R 37, 38
R39, 40
R41,4 2,4 3,44
R45, 46
R47,48
R49, 50
R51- 52
R53- 54- S8
R55,56
R57, 58
R59, 60
R6 1
R62
R6 3
R64
SI
S2
83, 4
S5
86, 7
S8
TI
TBl,2
TB3, 4,5
3003 4
54000
5400 1
DESCRIPTION
m I m ) /ST- 84
SECTIO N Vll
P ARTS LIST
I
(Cont ' d.)
SYM. '
STO CK'
AM'T.
TB6,7 , 8, 9,1 0
TB 11
TB 12, 13
T B14
T B15, 16
T B17
Vl,2 ,3,4,5
V6
X Fl
XU
XVl,2
XV3,4,5
XV6
54003
54006
54008
540 11
54014
54015
9003 4
90036
97800
977 12
97027
97025
97024
40000
4000 1
40007
40016
41008
41035
41047
41086
41090
4109 1
4 1096
41097
41099
41100
42000
4200 1
42002
42005
42007
42029
42055
43000
46011
500 12
50019
5002 1
530 47
530 48
53049
57000
58300
58303
58 408
58 410
584 12
58414
5850 1
80 119
81920
8 1175
8 1326
8 1327
8 1328
8 1329
8 1935
82 101
8953 7
89627
97300
977 17
66 107
66360
5
1
2
1
2
1
5
1
1
1
2
3
1
30
6
52
1
1
5
7
29
40
12
2
2
12
2
6
6
29
1
52
1
2
1
4
2
2
2
2
2
4
1
lengt h
lengt h
length
length
length
length
length
1
2
1
1
1
1
1
2
1
1
1
2
1
1
1
DESCRIPTION
terminal strip, 2 post
te rmina l st rip, 3 post 2 right
terminal strip, 4 post
termina l st rip, 1 post, dual upright
te r minal strip, 3 post 2 left
terminal strip, 3 post 2 left, with ground
tu be, 12AX7/ EC C83/ 7025
tu be, 6X4
fus eholder
pilot li ght ass embly
so cket, 9 pin mini atur e with shi eld support
s ock et, 9 pin miniature
s ocket, 7 pin miniatur e
nut, hex, No. 6- 32
nut, hex, 3/8" -32
nut, hex, No. 4-4 0
nut, hex, 1/ 2" for fusehold er
s cre w, No. 6- 32 x 1/ 2, binding head
s cr ew, No. 6, s elf tapping
s crew, No.8 x 5/ 16, self tapping
s crew, No. 6-32 x 5/ 16, binding head
s crew , No. 4- 40 x 5/ 16, bin ding head
s cre w, No. 4- 40 x 1/4, fl at head
screw, No. 4-40 x 3/ 8, binding head , brass
s crew, No. 6-32 x 5/ 16, binding he ad, brow n oxide
s crew, No. 8-32 x 3/8, se lf thr eading, brown oxide
s crew, No. 8-32 x l 3/ 4"
washer, lock, 3/8"
washer , fl at, 3/ 8"
wash er , lo ck, No.6
wash er , fla t, No. 6
wash er, lock, No. 4
wash er, rubber, 1/2 " fo r fuseho lder
washer, 5/8 ;' 0 .0.
lug, ground, No.6
(DOt, plas ti c
insulator for 500 11 (dual ja ck)
ins u la to r for 500 18 (t ri ple jack)
insulat or for 50020 (quadruple jack)
knob, concentric , inner
knob, co ncentric , oute r
knob, dual
lin e cor d
s paghe tti, sma ll
spagh etti, lar ge
cable , 1 conducto r, bla ck
cable , 4 conductor
cable , 3 co nductor
cable , 1 co nducto r, grey
wir e
pane1, (r ant
cable c lamp, metal
cable c la mp, plastic
chas s is
pane l, rear
hood
bottom pla te
brac ket , side
st ra in r e li ef
s hiel d, pilot bu lb
gl ue capsu le
s hie ld fo r 9 pin s oc ket
j ew e l, pilot bulb
manual of instructi on (wir ed )
m anu a l of instru cti on (kit)
PAGE 17
VI!!I!:l.
SERVICE WORK ORDER
Serial No.
Model No.
---------
Date
--------
Indicate red code numbers (if any) under words "INSTRUCTION MANUAL" on cover of
manual
-----
Check one: Purchased as kit
D
Purchased factory-wired
D
Name
-----------------------
Address
----------------------
Item (s) Returned: (specify any separately purchased accessories included in shipment,
or any detachable parts normally supplied that are omitted)
IU
Z
...
Q
IU
TroulJles and/or Repairs Required
----------------------
l-
ce
~
...o
~
IU
IL
e
Z
o
...ce
ce
Check one: Repair Unit & Bill
D
Send Quote Before Service
~
IU
Check one: Warranty Privileges Claimed
I-
Yes
0
No
D
D
If Warranty Privileges Are Claimed, Please Supply Information Required Below
•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
WARRANTY REPAffi REQUIRED INFORMATION
Date of Purchase
- - - - - - - Date Registration Card Mailed - - - - - - - Date Completed (if kit)
Sales Slip (or facsimile thereof) enclosed
Distributor
Address
I.E. 1368
Yes
_
0
No
0
--------------------------
--------------------------~
Electronic Instrument Co., Inc., 33-00 Northern Blvd., hI.C. 1, N.Y.
;;:
f,1
~
,
co
SECTION
TAPE/AUX
MX/AUX
FM-AM
TAPE HD.
PHONOA
PHONO B
MIC
N.C.
2-5,7- 12
4-5, 8-12
4-5, 9-12
5-6, 10- 12
1-7-8-9 10-12
1-8 -9 -10
1-7 -9-10
1-7-8-10
1-7-8-9
9-12
3- 10- 12
3- 4- 12
3-4-12
3-6 -12
2- 8-9
2-8-9
2-8 -9
2-8-9
INPUT
A,G
4- 5
N.C.
SELECTOR
B,H
1-7- 8- 910-12
1-7-8-910-12
SWITCH SI
:0;
~
...
"
C, E
7-12
D, F
2-3-8-9
8-12
2-3 -8
2-8-9
<en
•
P'
on
,
>-l
cc
•
...
~
g:
~.
>-l
~
r0-
O>
SECTION
MODE
SELECTOR
SWITCH S2
BAL.l
BAL.2
STEREO
REVERSE
MONO 1
MONO 2
MONO 1-2
on
,
>-l
...
co
A
2-6
N.C.
2-6
N.C.
N.C.
6-8
6-8
B
6-8
2-3-8
3-8
2-3
6-8
2-3-6
3-6
2-3-6
1) Entries are numbers of thos e switch co ntac ts which ar e connected togeth e r by the r otors at the particular position.
NC means no connec tion.
2) On s chematic diagram, all s witch wafe r s in the maximum counte r - cloc kwi se position (TAPE / AUX and BAL. 1) as
s e en from the front or shaft end.
E:iImJ
ST-84
1
PAGE 19
CII
330MtE
7-1~2
r -- -:-ll~S3A - ~
I
I
I
I ~~~i
O
X
R21
40 K
5%
RI9
6 SK
5%
0
~7
JI5
4 TAPEI
I
2
6
•
-
, ~?~"k1 3
~Pol2
5% MtE
-,
R32
RI7
1200
5%
r --
750K I.'
I
TAPE
MONITOR
SW
JI6 I
TAPE
OUTPUTI
11 0 12~'
2
0
10.
3
~ 04
~
o °5
o
7
+T
6
I
r - + --
-
I 4Ji~MF
II
12
I
0
0
2
9° / '
"---{ 0
0
7
I
I
I
00::
04
5
6
R2
47 K
J6
PHR2NO '---~----6-t-- ---'
R4
lOOK
J5 ...
__'
TAPE
10 °
9°
RIB
1200
5%
~~~
RI6
24 00
5%
5%
12
0
K
2
0
..r-..
'~
'---------;;a7
8 0
7
06
r:I --i- f--+ - ::lI
I
I
~
Ii.
HEAD
2
2" 3
PCI
6
t---'~
7
r--..L.
0 .1
400V
~~
!::B
JI7
~ CH. I
~ OUTPUT
r----'
I I
,...... 21
__--"t-t----'-1
7j
'
R53
500K
TREBLE
TI
5
I
,
I
3f--
I
I
I r - - -J
I
I
I
I
~J20 S;-
I
EUJ
$
JI9
I II
:Ji
C34 -r-
0.03 .
I
I
III~~~~~---'
R52
1M
BASS
I
I I
I
I I
I
I I
V5 B
12AX7/E CCB3
y
C30
0.1
R56
400V
33K
1
2
I I
I L __
I ,.
WHITEi"'o.",~--+-~~
BRN
v
I
R54
500K
TREBLE
. F igur e 5-6. ST -84 Sche matic Diag r a m
J
RUMBLE
FILTER
SW
I
I
I
I
SCRATCH
I
I
/
I
I
.b S7B
/
J
250 K
I
I
I
C24
V4
.0015
j"
12AX7/ECCB3
3
I
3
I
I
L ____ ..J
?
JI8
CH.2
OUTPUT
B
R42
22 00
R46
4701<
R48
33K
0C26
:£. f
2~
C28
0 .01
25V
2
Y C29
R55
33K
R51
1M
BASS
c> °5
I
1
7
12AX7/ECCB3
.J6fli 04
C23
.0015
R50 y C22
R40
C20
0.1
lOOK
220K 0.025
I 400V
6!::-1f-+-----,
V5 A
I
I
R43
2200
y
~
II
R47
33K
I
r.'~R=36::-1
I
I
~
9S7A
/
I
CIB
R41
2200
I
sw
IJ}
750K
\
2.7 K I
I lCI5
1.0.2
I lOY LEVEL
I
CONTROL
I
2~5V
IS6A
LOUONESS
UlL.....<_:lJ tl
R34 10-
1000S~
I
R37 \
I
C27
0.01
V
On.:
U. -,
I~~F
I
I S4 B
- t + +-f--;I+
-
R6~
2ooK .5%
C21
0 .1
400
7
\
B
CAONLANCE
TROL
I
I
R24
I50K
R35
250K
CI7
I+
I S5A
I
lOOK
,
I R331-
6 .8 K
C25
0.47
R49
lOOK
1
B
y
OUTPUT
S4A
~-jr
I
RI
471<
R3
." I
~/\~
, 4
~ T\ 05
I
Rl5
2400
5%
II
10L QI.. ....-<
°",3
3-3/4
I MXI
hik
I
R31
6.8K
R27
680K
R25
I50 K
R44
2200
S6B
t
ANOTHER
PER FO R MAN C E
PROVEN
PROOUCT