Roberts 1640 User manual

SERVICE
MANUAL
1B40-1B50-1BBDD-1B70
TAPE RECORDERS
~ ·
_;. ,, ~·· IMJ
$2.50

MODELS 1640, 1650, 1 6600, 1 670.
!KEYED TO ILLUSTRATION AT RIGHT!
1.
Supp ly Re el Hol der
2. Suppl y Reel
3. l e ft Chan n el Spco~cr
(Not in 1660D. Ou t board In 1670)
4. Tope Guide Roller
5. Automa ti c Shut- Off l ever
6. Drive Cop1tan S tora ge Post
7. I
ndex Count er
8. Editing Guide
9. Ta ke - up R eel Ho ld er
I0. Toke- up Reel
I I . Right
((ronne l S peak er
(Not in 1660D. Ou tb oa rd in 1 670)
12. Drive Capst an
13. Pi nc h Wheel
14. Pau>e leve r
15 . R ewi~d / Fasl Fo rwar d Co ntro l
16.
Stop / Storl Co n1 ro l
17. l e
ft Channel Miaophonc Inpu t,
18. Ri ght Cha nn el Microphone I npu t
19. l e
ft Channel Volume C on trol
20. le ft C hann el VU Meter
(Oual Purpose Me t er on Madel 1640)
21. Modl!l 1 640 : le ft / Rig hi VU Me ier S wit ch
Model. 1650 an d 1 670 : Mo nilor - Norma i· Mul e
Speqkcr Switch
Mod el 1660D: R/ l - NOI'I!IOI • l / R Channe l Tr ansfer
Sw it ch
22 . Right Channe l VU Meter
(N ot in Mo d el 1 640 )
23 . Ri gh t Channel Vo lume Control
24. L ef t Channe l Play/ Record Sw it ch
25. Right Ch anne l Ploy/ Record Sw it ch
26.
Ton e Control
27 . Power Switch
28 . Record I ndicator li gh t
29 . Power Cord Conn ectio n
30 . St ereo He adphone J ock ( 1650 & 16 70 J
31. Right Hum Ad justment
32. l eft Hum Adjustmen t
33. R ight ChoM cl Preornp Ou tp ut ( 164 0, 1650 , 1670 I
34. l C! ft Chonnel Pr,omp Outpu t ( 164 0, 1650 , 1 670)
35 . Right Channe l Phono/ R od io Inp ut
36. l ei I C hann el PhonofRadio In put
37 . Ri ghi Cha nn el Speaker Output (I 6 40 . 1650, 1670)
38. Left Channel Sp eake r Output ( 1640, 1650 , 1670)
39 . Right Channel Tw eeter Oulpul ( 1650, 1670)
4 0. Loll C hann el TwDet cr Ou t put (16 50, 1 670)
4 1. R ig hi Cho nnol High Levol Ou t put II660D on l y)
4 2. l ei I Cllonnol Hi gh Level Ou tp ut ( 1660D o nl y)
43. Ri ghi Channel Low Level Output ( 1 660 0 onl y)
44 . l ell C honn al l ow level Ou tp ut ( 1660D onl y)
IDENTIFICATION
CHART
Ll V)- --"'~- - -,
{ll) l-- -- - -=-==='-'

FUNCTIONS OF CONTROLS
Power Switch:
Moving Lhe power switch to the ·' ON " posilion applies
power to the motor and amplifier. In the " OFF " position,
power is cut off to the entire unit .
Volume:
A separate volume control is provided for each channel.
The volume control varies the playback vol ume, and the
record level when making a recording.
Tone:
The tone control setting determines the [re guency r e-
sponse of both amplifiers. Tone controls do nut. work during
record.
VU Meters:
The VU Meters are used to monitor the record level
when recording, and to balance stereo play. Meter indication
sho uld be between - 3 and -7 for best recording results.
Record Switches :
To operate, depress either or both record switches, then
t urn the stop / start conh·ol to "start. .. This holds the record
switch in record mode .
When the stop / start control is retu rned to " stop, " the
record switch automatically snaps back to play mode_
Channel Transfer Switch: (1660 -D )
This switd1 inte rnally tr ansfers the output of one chan-
nel over to the input of the other channel. A microphone
or radio / phono addition is added to the transfer receiv-
ing channel during recording.
The process may be r epeated back and forth between
c
hann els to make a multiple recording.
Tape Lifter:
The tape lifter is under the head cover and is operated
by the stop / start control. When the stop / start control is in
stop mode , the lifter pushes the tape away from the h eads
to pr event excessive wear du ring the fast rewind and fru;t
forward oper ations. This also mules the ~ound during these
modes.
Stop-Start:
Starts tape movement i11 "Play' ' or "Record" position.
Stops tape mo vement when moved lo the "Stop'' position.
Rewind - Fast Forward:
Fast Fo rwa rd position advances U1e tape on to the take-
up reel at a fast rate of speed. Re wi nd position wi nds the
tape onto the feed reel at a fast rate of speed .
Pause Lever:
In t.he "Up ' posilion, pinch roller is moved away from
capstan, and take-up tor que is r emoved from take-up spin-
dle. Tape stops instantly. This permits an adjustm ent of
the record level without tape movement. \Vhen lever is re-
tmned to "Down" position, the t ape movement begins.
Index Counter:
Pr ovides a means of locating desired select ions on a
reel of tape without skipping and h un ting .
Hum Adjustment Controls:
On Lhe l' ear paneL next to lhe A.C. Receptacle are two
openings,
these are the Right and Left Channel hum ad-
justing Potentiometers. They are screw driver adjustment.>.
Without tape on the unit, turn the volume up full and ad -
just the cont rols for minimum hum on each ch ann el.
Auto-Stop Switch:
When tape holds the aut o-stop switch ''U p," the motor
circuit is completed and the motor runs. If the tape br ea ks,
runs out, is of insufficient tension, the switch lever fails,
breaking the circuit, shutting off the motor.
IN PUT AND OUTPUT JACKS
Microphones :
A microph o11e input is provided for each channel.
These input jacks are located on the front panel to the left
of the left cha nn el volume control.
Note: When using the P hone-Radio inputs, the mi-
crophone plugs must be removed from the mi-
crophone jacks.
Phono-Radio Input:
Each channel is provided with a Phono -Raclio input
for making direct rec o rdin gs from a radio. phonograph, or
tuner. Th ese inputs are located on the rear panel.
Outputs:
1660D . .. There are two high and two low level preamp
outputs. each adjustable by the volume cont rols. These out-
puts are used to collllect the 1·ecorcler playback system to
an external power amplifier. The output jacks are located
on the rear panel.
The high level outputs are used with standard tube
type amplifiers that have tu_ner, auxiliar y or othe r high
level
inputs.
The low level outputs are for solid state amplifiers .
Te5ts will show
which is best for each individual case.
The high and lo w level outputs are low impedance cath-
ode follower outputs allowing for lvnger interconnecting
c.:ables without l ine losses.
1640 .. . On the rear (Janel are two external speaker jacks
and two high impedance pr eamp outputs.
1650 & 1670 . . . Ha s the same outputs as the 1640, plus
two phono type jacks for extension speakers to work with
the internal speakers. There is also a stereophone jack.
3

4
PARTS IDENTIFICATION
Fig. 2. Top View of Tape Transport.
OPERATING INSTRUCTIONS
Hook-Up Procedures: (1660-D)
1. T he outputs, high and low level ar e cathode follower.
low
impedance preamp outputs.
Th e instructions of the externa l power amplifier and or
t
un er should be followed. However as a rou gh guide the
following may be helpful.
I
nterconnecl .. . .
Hi gh l-ev el Output .. . to .. Tube amplifier .
·
a. Hi gh level i np ut
b. Auxillary input
c. Preamp input
d. Tuner input
Low Level Output ... to .. Transis tor amplifier.
a. Input
b. Preamp input
c. Tu ne r input
d. Auxiliary input
Rad / Ph ono I nput ... to .. Tuner Output
to .. Amplifier T ape Ou t
to .. Amplifier Pr eamp Out
to . . P hono. Ceramic Cartridge
to .. Ph ono. Pr ea mp Out
to .. parall el w ith TV spe aker s
to
.. parallel wit h Radio speakers
Thread i ng the Tape:
1. Place a full reel of tape on feed spindle. P lace an empty
re el on t.ak eup spindle. Secure reels in place with rubber
r ee l holders provided.
2.
Unwind aboul 14 inches of tape from feed r ed. H"old a
section
of tap!' taut and thread p er ph oto . Make sure
!.ape pulls automatic tape shutoff switch arm u p to "On "
p
o.> ition.
3. T nsPrt fre~t end of tape into one of t he r adial slots in hub
of takeup reel. Ho ld tape end in place and turn r eel
seve ral turns co un terclockwise to secure tape to the reel.
To Make a Stereo Recording:
1. Connect reco rder to 110-125 volt 60 cycle po wer so ur ce
with power cord provided. Tur n power s witch to " Po wer
On.''
2. Thread the t.ape. Set Index Counter to zero.
3. Co
nn ect signal sou r ce to proper input.
a. If microphones ar e used connect them to microphone
jacks. Level will be contro lled by the vo lum e c ontrols .

Fig. 3. Bottom View of Tape Transport.
b. If a phono or radio source is used connect their out-
puts to the respective channel Phono - Radio input
jacks. Level will be controlled by the volume controls.
4. Push Pause Lever to "Up" position.
!i. Hold record switches depressed.
6.
Tum start / stop c ontrol to " Start" po s it1 on. This hold;;
the record switches down in record mode.
7. Start signal so ur ce to set recording level. VU Meters
should read -3 to - 7 on the average .
8. Release the Pause Lever (down) to start tape. Tracks
1 and 3 are now being recorded.
9.
When recor ding is completed, or when the end of the
reel
of tape is reached, return start / stop control to
·
'Stop'' position. Record switches are automaticaUy re-
leased to r eturn to play position.
10. T o record tracks 2 and 4, remove full reel from take-up
spind le . turn over and pl ace on supply spindle. Proceed
as in steps 2 - 9.
To Play a Stereo Recording:
1. Co nnect recorder to proper power sour ce with power
cord provided. Turn power switch to "Power On."
2. Thread the tape. Set Ind ex Counter to zero.
3.
Locate desir ed start i ng point by using Fast Forward-
Rewind kn ob while observing Index Counter.
4. Turn Start-Stop knob to " Start" position. Adjust volume
for each channel. Both tracks of a 2-track ste reo tape or
tracks 1 and 3 of a 4-track stereo tape will now be played.
5. Tape may be advanced rapidly or rewound, after Start-
Stop knob is placed in · ·stop " position, by using F ast
Forward-Rewind knob.
6.
To play tracks 2 and 4 of a 4 -track stereo recording after
tracks 1 and 3 have been completed , do not rewind tape.
Remove full ree\ from ta keup spindle, turn it over. and
place on feed spindle. Proceed as in Steps 2-5 above.
Monaural Recording and Play bac k:
Proceed as indicated for stereo operation but use only
jacks. contro ls and switches for one channel. Volume con -
trols for the unused c hannel should be set at ze ro.
To record four monaural tracks. use left channel f ir st.
recording track 1. Reverse tape by removing full r eel from
Lakeup
spindle, turning it over. and placing it on the feed
spind le. Continue to use left ch annel while recording track
4. Reverse tape and use right channe l to record track 3.
Rever.se
tape again and continue to use right channel in
order to record track 2.
To play back four monaural tracks. use the same sequence
of tape sides and recorder channels as when recording.
5

6
SOUND - WITH-SOUND RECORDING
This is a procedure by whi ch you may record yam fa vorite orchest ra on one channel, and then play or sing with t he re-
cording
in suc h a manner as to make the playback sound as t hough you were " right there .. with the orchestra . Or it ma y
be used for language study. with the teacher 's voice on one channel and your re spo nses which may be erased and re-re
corded as often as desired) on the o ther channel. ROBERTS Langua ge Lab o rator y Tapes. available from your Robe rts
de aler , have tne instru cor's voice pre-recorded in this manner in fo ur differe. nt language s.
PROCEDURE:
1. Make a master recording on Trac k 1. using Left chrumel only . Turn Right channel volun1e controls to zero and fol·
low
procedure m1der " To Make a Stereo Recording ," using L eft channe l only.
2. Rew ind tape .
3. Re co rd on Track 3, using Ri gh t ch ann el only while listening to Track 1.
4.
Rewind t.ape.
5. Play back re co rd ing, as in stereo play . Master rec or din g will be heard on L eft channel and added reco rding will be
heard on the Ri ght ch ann el.
6. Track 3 may be erased and r ereco r ded without di s turbing master t rack by repeating Steps 2 through 4.
SOUND-ON-SOUND RECORDING (1660D ONLY)
1. Make original recor ding on Track 1 usi ng L eft channel only. Turn Right channel volume cont rol to ze ro and follow
proced ur e unde r, ''To Make a Stereo Recording."
2. Re wind tape to be ginning of original recording.
3. Set Channel Tran sfer Switch io "L to R" position.
4. Pu sh Pa use Lever up to " Stop '' position.
5. H old Ri g hi Reco rd Switch depressed and turn Start-St o p knob to "S tart'' posi tion .
6. Connect Right challllel microphone . Appl y sig11 al to microphone and ad just the Ri ght cha nn el volume c ontro l fo r ap-
proximat e ly half the normal re co rding level re ading on the Right c hannel VU Meter.
7. DO N0'1' READJUST THE RIGHT CHANNEL V OL UME CO NT ROL AFTER PRESETTING FOR THE MIC-
ROPHONE RECORDING LEVEL. (V:! •Jormal)
8. R elea~e Pau :e L ever and make a tdal recording of the Lef t cba~el trSllSfer and the R ight channel microphone added .
9. Adjust the L eft channel volume cont rol only, while watching the Ri ght channel VU Meter readin g. Th e Righ t chan-
nel VU Meter should be read ing full normal. Ha lf of the reading will be the L eft cbrumel tr ansfer ru1d the other half.
the Ri ght channel micr opho ne.
10. Rewind the tape. play the trial recordin g. If the test run was satis fa cto ry. proceed with the final recording by re-
peatin g St eps 2 !hrcu gh 9.
11. Play back rec ording. So und - On-S ou nd re co rdin g is on Tra ck 3 ( Right channel ) so volume controls for Left cha nnel
sho uld be set to zero. (N OTE: The original Track l recording of the L eft amplifier is still intact at this point, so
Step s 2 through 9 may be repeated if the final re cor ding was no t satisfactory .)
12. The abo\·e process ma y be repeated, using Tra ck 3 as the original reco rding and add more ma te rial to it for a rnul-
tirl e reco rdin g. In this case the Channel Transfer Switch should be se t at "R to L" position, and the L eft channel
microphone input will be used.
ASSEMBLY - DISASSEMBLY
Assembly (mounting): (1660-D)
1. Check for dearance, (deck & prean1ps, reels, ease of op-
eration. etc.). Transfer cutout pattern from template to
panel. C ut out panel open ing.
2. Rem ove side angle bra::k ets {rom metal cage.
3.
In sta ll un it into panel cutout.
4. R einst all side angle brackets onto rne.tal c age , and press
up against underside of panel.
5. If panel is .1f2" or mar~ thick, fasten angle brackets from
underside w it h wood screws, into panel.
6. If panel is less th an
1
/2" thick use fanc y headed bolts and
nuts clear through panel.
For Access to Top of Tape Deck:
l. Remove Start-Stop Jmob an d Fa st F orw ard -R ewin d kn ob.
2. Remove 3 tr ansport deck mounting screws, c ap sta n bush-
ing
sto ra ge r ost .
3. Pr y o ut pinc:hwheel cap. take o ut pinchwheel mounting
screw. and lift oU pinchwheel.
4. Remove bc>th reel tables after taking CJ ut re el table
screws. Note hu m ber of fibre spacers und er reel tables
as th ey are removed.
5. Lift off transport deck panel.

MAINTENANCE INSTRUCTIONS
LUBRICATION
L ubricate the following parts every th<ee months when
the <eco rder is subjected to heavy usage. every six months
under mod erate usage, and once a yea r unde< conditions
of occasiona1 use.
l. Feed and take-up spindle sh af ts with two drops of light
machine oil on each shaft.
2. Rewind idler bearing and wind idler bearing . with two
dr ops of Light ma ch ine oil on each bea r ing .
3.
Apply a liberal amount of light grease to each roller and
on all levers and cams .
4.
Sa tuTate the felt washe r in the re t ainin g cup of the
drive capstan with light machine oil.
Caution: Do not allow grease or oil to remain on any of
the drive surf ace s, or on plastic su rfac es or any part touch-
ing the tape.
CLEANING
The capstan, pinchwbeel, tape guides, and .reco.rd/ play
head and erase head accumulate a tape oxide coating as
the ta pe passes these parts. Clean these parts pe riodically
with a soft cotton swab dipped in alcohol.
MECHANICAL ADJUSTMENTS
1. Record-Play Head
Heigh t -L oosen the two mounting nuts at the side of
the .he ad mounting bra cket. Move the head so that the top
pole piece is even with the top edge of the tape. Gently
tigh ten t he nuts.
Azimuth -Pla ce a prerecorded azimuth alignment tape
on the recorde.r. While playing tape alternately t ighten
up per and loosen lo wer head mo u nting nuts or vice versa
until position of maximum output is found.
2. Erase Head
The erase b ead hei gh t is adjusted in the same manner
as th e Rec ord -Pla y head.
3. Brake Shoes
When br ake shoes become worn, loosen the mounting
scre ws a nd rotate the shoes a few deg r ees until a new brake
surface is exposed to the supply and take- up reel discs.
4. Rewind Idler Wheel
To bring the wheel in alignment with the rewind reel
shaft adjust both the idler load spring and the rewind roller.
The press ur e on the knurled motor bushing shou ld be about
50 gr ams durin g th e rewind operation.
5. Pinch Wheel
To bring the wheel in ali gnme nt with t he capstan shaft
adjust th e pi nch w.heel load sp r ing. The pinch whee l pres-
sure shou ld be between 1,000 and 1,150 grams whe n the
unit is operating at 7% ips.
6. Rewind Intermediary Idler
Adjust the intermediate wheel sp ring to obtain about
50 g ram s of pressure equally exerted to both the rewind
idler wheel and the rubber ring on the supply reel shaft
assembly . Make adju stment in the r ew ind mode.
7. Supply Spindle Tension
A c han ge in to rqu e is accomplished by either adding
another metal washer next to the one in the clutch assembly
which increases tension, or by removing the exist i ng one
w hi ch has the reverse effect.. See explo ded view for location.
The r eq uired tensi on is determined by placing a s tand-
ard seven inch r eel with a two and one fourth (21,.4) inch
hub diameter on the supply spindle. The re el should have
twenty six feet of leade.r tape wound on it. Attach the end
of the leader t.ape to a scale with a range of 0 to 250 g rams.
Position the scale vertically with respect to the re el hori-
zontal axis. Exert a ste ad y pulL The r equ ir ed to rque should
be between 145 grams and 160 grams .
8. Take Up Spindle Tension
Th e procedure is identical as the supply spi ndle, ex -
cept the r equired t orque is between 180 g ra ms and 220
gr ams.
7

8
GE NERA L TEST PROC E DURES
NOTE: Wh enever an ex te rnal test instrum e nt is used from an a mplif ie r ou tput, an 8 ohm resistor sho u ld be placed
acro ss the amplifi er o utpu t or the test in strument input , if the use of the test instrument diseng age s th e
amplifier speakers.
II Prea mp out pu ts are used for measureme nts , us e a 270K 1W load r es istor.
Durin g Record modE'. an int e rn al 8 or 10 o hm dummy load resistor is au tomatica Ti y inserted to re pla ce
the speake rs.
Anytime a high level signal
is u se d, the wavPform mo uld be ch ec ked for d jstort ion on an oscilloscope.
Outpu t:
Pla y back at full ,-o lume and ton e. a 700 cps ton e. recordE'd at 0 ob. as meas ur ed on an external l abo r at or y
type VU Meter.
Measur e th e output on th e s am e type exte rn al VU Meter with the recorde t· termn ate d into 8 ohms.
Square the resultant voltage n•arung from th e VU Me ter an d di v id e by 8 o hms to get th e RMS power o utput
in watts. (P =E2/ R) .
Si gnal - To-Noise :
Pl ay back a 700 cps tone pr e-recorded at 0 db, as measur0d on an external laboratory t ype VU Meter.
Adjust th e re corder vol um e control until an exte rnal VU Meter fr om the output reads 0 db.
Without changing the record er volume control sett ing , stop the tape motion wHh the Pau se Lever and 1·ead the
e xternal VU Meter. The VU M ete r is now reading r es idual noise on ly, no signaL
Th e reading in db of the residual noise level at t hat vo lume sett ing is the signal/ no i se ratio at 0 db level.
Frequency Response :
NOTE: F ir st cl ean and demagn etize an d adjust azimuth of the heads.
Set the counter io '000' a nd reco rd a -12 db line input 700 cps tone at -1 0 db as measured on an exter-
na l VU Met er. ( If in put me ter no t avai lable, set record er volume control 1/.t turn open an d adjust the os-
cilla
tor output , for -10 db amplifier out pu t.)
R
ec ord th e 700 cps tone at - 10 db f or 10 digi ts on the counter, the n c hang e tones on the oscillator fo r 10
di gi ts per tone. without changing the oscillator output level or the record er volume control se ttin g.
Th e tones to be reco rd ed after the 700 cps reference ton e are 50, 1 00 , 250, 500, 1000, 2.5K , 5K, 7.5K, lOX ,
12.5K,
15K , 16K , and 17K cp s for 10 di g it s each.
After recording above, rewind
th e tape to th e beg inning '000', and set the tone control for the ' fl at' se tt i ng for
the speed
that is be in g used.
Play th e 700 cps lo ne referen ce frequency at the begi nnin g of the tones an d ad just the recorder vol ume for an
ou tp ut of - lO db on an ex tern al VU Meter. Do not ch an ge th e volume or tone c ont ro l sett in gs after th e 700 cps
-lOdb is sd.
R ea d the external VU Meter evpry 10 digits as the tone changes from the 50 cps to 17K cps .
The v
ari ati on ::. from th e - IOdb, 700 cps referen ce frequency original setting, is the frequency respons e,
w hi ch may be plo tte d on log paper f or a curv(' o1 · simply by the numbers.
Wow And Flutter:
Play back a 3000 cps st and a rd prerecord ed wow and flutt er tE'st tape, that guarantees a wow a nd flutter wit hin
.07%. a nd read the E'ffeclive v alu e on a wow a nd flutt er meter.

SPEC~ & PROCEDURES
Hum
At max. volwne -30 db ( - 40 db at preamp )
At min . vol um e -60 db
Signal-to- Noise Record to Play -43 db min.
Pre-recorded - 44 db min.
Wow & Flutter .2% max at 7%
.3% max at 3%
Tone Conlrol - 12 db at 10KC
+13 db at lOKC
H ea d Current (OSC, Fr eq. lOCke)
Erase 12 MA to 15 MA
Bi as .54 MA to .56 MA
Record .029 MA to .031 MA@ lKC
Power consumption at 117 V.A.C. 60 cps 55W (1660D) BO W (1640-1650-1670)
Erasure R ecord/P lay at 0 db, 1000 cps
-42 db using 1KC filter
Fus e: 1%A. 250V.
Gain from
sta ndard operating l eve l pre-recorded tape
7¥2 ips volume full .4 vo lts at preamp minimum
<!MV at 700 cps head input = .25 vo lts at preamp minimum
2 MV at mike for 0 level record
125MV at pbono for 0 le vel record
Cros
sta lk
Reco rd Ch # 1 at 0 db , 700 cps
Play Ch #2 at same set ting that Cb # 1 is set at for .25 V output on Ext. meter at preamp output -55 db min.
Cross Channel R ejec tion
Reco
rd both channels at 0 db, 700 cps
Play tape and set both channels to .25 V at preamp output
Re verse tape and play -55 db minimum
9

-
00
TAPE DECK PROBLEMS
j Capstan does not rotate.
Troubles with motor
-"'
1
~,oken field coil. Check field coil with tester, and replace motor if coil IS broken. I
HDefective motor starting capacitor Replace
I
H Rotor shaft dragging due to lack of oiL
Overhaul motor. Clean and re·lubncate oilite metal. \
y Some foreign matter exists between rotor and stator.
Check and eliminate foreign matter for free rotation of rotor. 1
Troubles with
power transmission r- ---1 .
Replace belt. I
mech.anism.
Broken capstan dnve belt.
---i Capstan drive belt off of driving position.
Place belt in position. I
-1 Motor bushing slippmg on motor shaft.
Tighten mounting screw. \
-i Oil attached to motor bushing and/or flywheel Wipe
off oil with cotton swab soaked in alcohol. j
r1Decreased motor torque.
Check motor torque
and replace motor. j
I Capstan rotates in Stop position, but
I
tape does not advance when switched
Troubles With motor.
WDefective
Replace
to Play pos1t10n. screw. 1
Motor bushing slipping on motor shaft.
Tighten mounting
Troubles with power transmission f-rl_
mechanism. Capstan drive
belt stretched
Replace belt. I
HOil
attached to motor bushing and/or flywheel. Wipe
off oil. I
H Capstan bushing sllping on flywheel shaft.
Tighten capstan
mountmg screw. I
H Excessive tension in Takeup/Supply reel table assembly.
Readjust tension.
!.
rl_Oil attached to capstan and/or pmch wheeL
Wipe of oil. I
Y Insufficient pmch wheel pressure.
Check and re-adjust pinch wheel pressu,re. I
!.Capstan advances tape.
but take-up reei-rl Reel shaft dragging due to lack of oil. Check take-up
reel shaft assembly.
1
Overhaul reel shaft assembly: relubricate. Replace
I
does not take up tape. H
Take-up idler wheel does not rotate properly. Check idler wheel. Replace if necessary. I
reel shaft assembly If not repairable.
HOil attached to idler wheel and or ro-
ller on take-up reel shaft assembly. Wipe
off oil. I
Y Take-up idler whee! does not keep good contact.
Check idler tension spnng. Replace spring if necessary. J
Check lever
J
ITake-up flinctwns normally. but tape jrl Troubles with motor. w
Rotor shaft dragging due to lack of oil. Overhaul motor. Clean and
re-lubricate oilite metal. J
speed lower than regular speed.
Defective motor starting capacitor
Replace I
~Fluctuation in power supply.
Check line voltage and cycle. Use voltage regulator 1f line voltage is lower than standard. I
Troubles with power transmission
Qlpstm drive belt stretched
mechanism.
and slipping on motor bushing
Replace belt. I
Capstan drive belt not in correct driving position.
Place belt in position. J
Oil attached to motor bushing and/or flywheel. Wipe
off oil. I
!wow· flutter. Irregular tape movement. r- ---1 Troubles with motor. Rotor shaft dragging due to lack of oil. Overhdul motor. Clean
and re-lubricate oilite metal. J
W Defective motar starting capacitor Replace I
~Troubles with power
transmission r--
Check reel shaft assemblies. Replace reel shaft
I
H Take-up, supply reel shaft dragging or excessive tension.
assembly if tension not adjustable.
mechamsm. H
Capstan drtve belt stretched and slipping.
Replace belt. ]
HUnbalanced flywheel rotation.
Check balance. Replace flywheel. I
H Rubber on pinch wheel
deteriorated. Replace pinch wheeL I
H Pinch wheel or tape guide does not rotate smoothly.
Check and replace defective part.
Clean and re-oil I
if it again provides smooth rotation.
H Dust on heads. Clean heads. I
H Insufficient pinch wheel
pressure. Re-adjust pinch wheel pressure. l
H_ Gapstan bushing slipping on flywheel shaft. Tighten capstan mounting screw. I
Y Worn-out
idler wheel or no
oil.
Replace worn-out Idler. Lubricate oilite metal in center of idler. I
IUnit does not operate in Fast. ForwardJ-n
Troubles with power
Oil attached to take-up idler wheel or motor
Wipe off oil. J
Take-up reel shaft does not rotate even
without placing recording tape on unit. transmission
mechanism.
bushing.
Loose motor bushing.
Tighten motor bushing moWlting screw. l
Take-up idler wheel does not fllilction properly.
Check and readjust idler wheeL I
Take- up reel shaft assembly does not function
Check. clean and re-oil reel shaft J
properly.
assembly.
Check
lever
I
/Check motor torque.
Replace mo -~
y_ Take-up reel shaft does not rotate when
recording tape IS placed on unit.
Troubles with motor.
Decreased motor torque.
tor if required.
Defective motor starting capacitor
Check and replace
I
I Troubles with power . ~
Excessive slippage of clutch mate-
rial (felt} in take-up reel shaft
Check take-up reel shaft assemblyj
J transmission mechanism. assembly.
I
Tape guide roller does not rotate smoothly.
Check guide roller. Re-Oil or replace.!
Take-reel warped and sticking to
Defective reel.
Check and replace reel.J
deck top panel.
I f-~ Supply (rewind) reel shaft does not rotate
Troubles with power trans-
Oil attached
to rewind
idler or mo-
Unit does not rewmd tape. mission mechanism. Wipe
off oil. l
even without placing recording tape on unit.
tor bushing.
]Intermediate
idler(black bakelite
Check internal idler. I
I
wheel}
not working correctly.
Loose motor bushing .
Tighten motor bushing mounting screw. l
. jRewind
idler does not rotate or not
Check rewind idler. Clean and re·Oil-l
Jin position.
~upply reel shaft assembly does no
Check supply reel shaft assembly. I
~tate smoothly. Clean and re-oil
y Supply (rewind} reel shaft does not rotate
rrlTroubles with motor. ]Check motor torque.
Replace motor I
Decreased motor torque
when tape is placed on unit. lif
not repairable.
Defective motor starting capacitor Replece I
Excessive slippage of clutch mate-
~Trouble with power trans-
Check supply reel shaft assembly. I
mission mechanism.
rial (felt) in supply reel shaft assembly.
Loose tape winding after being
placed in Rewind or Fastforward
mode.
Tape spills when stopped from
Rewind or Fast forward mode.
Break does not functwn properly.
PenodJcal clack noise when
rewmdmg
or fast forwardmg tape.
Loud motor VIbration.
Y Defective reel.
Decreased back tenswn of take-up and supply reel shaft
assemblles.
Excessive sllppage of felt clutch matenal m take-up and
rewmd
reel shaft assemblles.
Reels of different s1ze are used. For example. 5· reel on
take-up s1de and 7~ reel on supply Side.
Worn-out
brake shoes.
Oil attached to surface of brake shoes.
Loose brake shoes.
Brake lever does not function properly.
Worn-out and
ragged Idler wheeL
Loose motor mountmg screw.
Defective motor starting capacitor
Tape gmde roller does not rotate.
Check guide roller. Re-oil or replace. _j
!supply (rewind) reel warped and stick-
Check and replace reel. l
ling to
deck top panel.
Disassemble
reel shaft assemblies and strengthen back tension.
Readjust slippage of felt clutch matenal.
Replace defective reel shaft assembly if this
readjustment IS difficult.
Always
use reels of same size on both Sides.
Check and
replace brake shoes.
Check and re-adjust brake lever.
Replace
idler wheel.

10
J
Modes of Operation
1al STOP
I
(b) FAST-FORWARD
c) REWIND
II
d) RECORDING
PLAYBACK
l01 IC
( v~
\.....
~-==-
Pinch
ITo!r.e-up [ !iewtnd
Take -
Roller
Idler Idler
up-s1de
Wheel Wheel Brake
X X X 0
X 0 X X
X X 0 X
0 0 I X X
N OT E S: X-m arks indicat es ~o p en" and
0- marks "engagedh
Supply-
side
! Brake
0
X
0
X
FAS T -FORWARD MECHANISM
Turn the FAST FWD - REWTND knob (Al to ~F AST FWD•
position,
and the cam (B ) under the knob pushes up
the Lever (C). The Tdler tDJ moves in to the space
between the Plastic Roller IFl above the Take-Up Reel
Sp mdl e and the upper part of the rotatin g motor driv
bushing to transmit the motor rotation to the take - up
reel spindle. At the sam e time, the brakes (H ) and {I)
come off the reel spindle to free the Supply Reel Spindle
(G l, thereby allowing fast winding of th e tape onto the
take-up reel.
Fre e Rotation High - Speed Rotation
RE WI ND MECHANISM
Turn the FAST FWD-REW I ND knob fA) to "REWIND~
position, and the cam (B) under the knob pus h es the
Lever ( C) up. The Idler (D) moves into the space bet -
ween the upper part of the rotating Motor drive bushing
(E) and the Intermediate Pulley (F) to transmit the high-
speed rotation of the motor through the Int ermedi a te
pulley to the Supply Reel Spindle (G). At the same
time, Brakes (H) and (I ) come off the reel spindle to
free the take-up reel spindle r n. thereby rewinding the
tape in to the supply reel at a fast speed.
High-speed Rotation Free Rotation
~tP · ;..~
~ ( II ' (\~ 0
0 "--.__/ ·J '-......-/ r '
\.-; , i I I~
Q____D--o
0
I
ST OP CONTROL
Push the Stop lever to qSTOPh position, brake rubber
(A ), and (B) depress reel spindles to stop rotation of the
reel spindles.
As
brake rubber depresses the plastic rollers under
the reel spindles, no friction works on the ta pe itself.

(2~)WASHER
FELT WASHER
~SCREW(2)
~ REEL TABLE ( 3)
c:::=====t=:s::P===:f
SPINDLE TABLE (z Y)
FELT WASHER
.....----- DRIVE RING {).5)
~S CREW
' REEL TABLE
SPINDLE TABLE
FELT WASHER
CLUTCH
PLATE
SPR I NG ( :z 7}
WASHER - -------.
_ _ --- ®RETA INING RING
===t==== CLUTCH DISC
_ _ __ @RETAINING RING {29)
C::::==l===:r CLUTCH DlSC ( 3o)
WASHERS-- ~~~~ ~~
STAR SPRING WASHER (3J) --- --- ~~ ~a===::::~ - WA SHERS
(:2-g)
(33 ~- ..... ,
__ _ !3) _ 6RETA INING RI NG (zq) __ - ®RETAINING RING
~~~~ --~ ~ ---- - SCREWS-- --------~~--~~~
H~~~~:JIW E~fS~ S~P~I~N=DL:E~('i?~~N Tt NG p LA T~E :=:~;;~ ~ftf~~s:
1
~
1
/.,B ASE PLATE
~ NUT ------------~--~ ~ r-~
SUPPLY REEL SPINDLE ASSEMBLY
TAKE-UP REEL SPINDLE ASSEMBLY
# 62-49
#62-50
5-2 0- 64
A
DATE REV . APP .

N
0
"RAD./PHONO
'-
MI c 'ROPHONE
'-
.------11~~ 12AX 7 r-- ~ 12AX? 1- +--e ----: ~:»...,.t---1 ~1'2AU? t------t~ 12AU7
r--tcATHODE VOLUME C.A.THOl>E CATHOt>IE
? CONTROL
{
~
CI-IANNEL..
TRANS.~E'R
SWI'T"C ...
R -L NORM. L. · R
, -- - ---- ,
; ' -- ~ -~·::
' -~ J -- ~
I "RIGHT I RIGHT
H l (ioH LOW
L.li.VEL L.EVIi.&..
OUTPUT OUT PLAT
STAGE ST.A.GE
'----e- -----+--to'" H I~H L-EVEL.
OUTPUT
&..OW LEVEL
OUTPUT
'B I AS.
'REJECT.
'PRE-
EMPHA~IS
NETWORK
~
1
T
.l
t
T
t
vu
METER
95 KC
~ECORl>
~lAS
'PUS.H-PUJ..L
.------!!~~ - --1 0 ~C IL L.ATO'R r---
':>l(ioNAL
12. AU 7 CATHOl>E
ERA~~
CURR£NT'
-- I
-- - 1-- --- - -y---- -o
'REC. "'REC. I
'REC. I
4 I
J'
-- - --
'PLAY
'PLA'(/R£C.
HE AI>
j_
.---._ I • I
'PLAY
'PL.Al
•
~
? -
? -
>
TONE
j C
ONTROL
'PLAY
I
BLOC K DIAGRAM MODEL 1660D
L EFT PREAMP ONLY
(Right Preamp the r,)

N
-
r--
"RE C .I
I
'P L A.Y
1
212AX7
CATHOD E
k 12AX7
FEEDBACK
-
'PLAY
'PLAY/REC.
HE.AD
VoLUt-IE
CoNTROL
TONE
CONTROL
l' 'R E.AMP
OUTPUT
'"R I GHT CHANNEL
~
----v- 0 ~TE REO
r------------1 l'HONO
s
r---- ,
.--~~~--• I
: MON. 1
I
'i'LJI.'Y I
2.
1. GBM8 1---4..._....,j Til.ANS 1--._-~...- I MUTE 1
~ORMlll I I
l ~- -
D
CATHODE
FEED ll£C. B
'!SACK
I
I
-I
I
BIAS
~
l
'REJECt T
'P'R E.- l
~
EM~A~ I S
T -
NETWORK
"l e: co~b 100 KC
StCaNAL B I A$ PUSH-PULL
osc.
CA T HODE. 12AU 7
'P L AY
BLOCK DIAG~MA MOOE. L I 650 - 1&70
L EFT AMP. OttLY
CRiiht amp . tile Scl~rte)

22
PLAYBACK PROBLEMS
1. NO SOUND.
(a) Pilot light and tubes do not light up and the motor does not run.
(1) D efective fuse.
(2) Defective A.C. cord or its connection.
(3) Defective power switch.
(b) P ilot light anrl tubes do not light up but the motor does run.
(1) D efectivc power transformer.
(2) Defective conn e-cti on in power transformer primary leads.
(c) Tubes lit. but no sounci from either channel. (not even faint bwn).
(1) Defecth·e re ctiUe r tube.
(2) Power supply component defective.
(d) One ehannel normal, other channel dead, (not even f aint hum).
(1) Speake r open or d. isconnected .
(2) External speaker jack de[ective.
(3}
Output tube defect.ive.
(4) Output circuit defective.
(5) Output transformer defective.
(e)
One channel normal. other channel has faint hum but no signa l so u nd .
(1) D efective head or head connection.
(2) Defective input or preamp tube .
(3) Incorrect voltages.
(4) Open coup ling c apacitor or shorted grid.
2. SOUND BUT WITH LOUD HU M.
(a) Hum controllable with volume control.
(1) Impr oper head lead shit>ld grounding.
(2) Misadjusted hum controls.
(3) DefectivE> input lubes.
(4) Improper h ea d l ead or input tube grid lead positionin g.
(5)
Leaky coupling capa citor.
(6) Gr ou nd loop between external equipment and re co rder.
(7) High resistive solder joint at g round connec tion.
(b) Hwn n ot controllable with vo lwne control.
(1) Defe ct ive driver or output tubes.
3. LOW VOLUME.
(2) Leaky coupling capacitor between driver and output tube.
(3) D efective power supply filter.
(4) High rE-sistive so l der join t at ground connection.
(a) Record sensitivity normal according to the VU Meter.
(1) Dirty beads.
(2) Tape threaded with oxioe side away from the nead.
(3) Defective bead.
(4) Defe ctive tape lifter .
(b) Re cord l<Pnsitivily also l ow acc ordi ng to the VU Meter.
(1) Defectiv e amplifier tube if only one side low.
(2) Def ective rectifier t ube if holh sides low.
(3) Defecti ve plate re s istor causing low voltage.
(4) DefectivP output transformer.
(fi) Leak y feedback capacitor.
4. DISTORTION .
( a) At low volume.
(1)
Defective tube.
(2) Tncorr ect plate voltages.
(3) Leak")'
coupling capacitor.
(b) At any volume but woJ:Se at high volume.
(1) Same as 4 (a).
(2) Defective loudspeaker.
(3) Defective feedback netw or k.
(4) Bad wow and flutte r in tape transport. (see deck problems).

RECORDING PROBLEMS (Prerecorded tapes play alright)
1. NO RECORD.
(a) VU Meter not working in record mode.
( 1. ) Defective microphone.
(2) Input jack contact poor.
(3) R/ P slide switch not functioning.
(b) VU Meter reads alright in record mode.
(1) Defective R/P head.
(2 ) Broken wire in record circuit.
(3) Defec tive re cord current cir cuit component .
2. DISTORTION.
(a) VU Meter & amplifier monitor normal.
(1) Faulty oscillator bias voltage.
(2 ) De fective r eco rd cur ren t circuit component.
(b) VU Meter normal but amplifier monitor distorted.
(1) Excessive signal input.
(2) Defe ctive R/P slide switch.
(3) D efect ive microphone or radio / phono .
(4 )VU Meter reading incorrectly.
3. ERASE PROBLEM .
( a) No erase.
(1) Faulty e rase head.
( 2) Faulty erase cable or con nec tion.
(3) Open erase coupling capacitor.
(4) Tape lifter not functioning.
(b) Po or erase .
(1) Dirty er ac;e head.
(2) Defective erase head.
(3) Low erase voltage.
(4) Def ective head elevation.
4. HIGH BACKGROUND NOISE LEVEL ON TAPE. (his s, sc ratch y)
(a) Hiss.
(1) Magnetized beads.
( 2) Defective tape .
( 3) ' Hash ' on oscillator output waveform.
(4) Dir ect current leakil1g to heads.
(b) R umblin g.
(1) Defective tape.
(2) Distorted oscillator output waveform.
(3) Excessive tape pressure against heads.
(4) Exces!iive tape 'wrap' around beads.
5. LOSS OF HIGH FREQUENCIES .
(a) No sparkle.
(1) Dirty heads.
(2) Record bias incorrect voltage.
(3) Wnrn beads .
6. LOW SENSITIVIT Y.
( a) VU Me ter reads normal.
(1) Dirty heads.
( 2) Def eciJve heads.
(3) Defective r eco rd current circuit component.
(4) Defective tape.
7. LOSS OF LOW FREQUENCIES.
(a) No bass.
(1) Mismatch of impedances of input.
(2) Incorrect sped. (fast)
23