Sony WM-10 User manual

TROUBLESHOOTING GUIDE
WM-10
m m u m STEREO CASSETTE PLAYER
US , Canadian Mode!
WM-20
_I_
AEP, UK , £ Model
Sony Corporation
TABLE OF CONTENTS
Description
Page
General precautions for repair.... .1
No operation ) ^
Noise when battery is. worn out (less than 0.9V) ) ‘ .
No power
LED does not light up
No converter operation
Converter board simple check method
Motor does not stop for FF/REW STOP...6
No muting
No sound (FWD, but no sound)
Low level
No Dolby
Hum noise during playback
Noise on L CH
No motor rotation
Motor coil check method
Fast 1 slow speed
No speed acceleration
Servo board (A) (fl) simple check method
Defective tape transport I., . .13, 14
Defective tape transport If ....15, 16
Repair know how ..... .1 7
.4. 5
. . .7, $
. 9—12
This book is for quick and easy repairing.
File with the sendee manual.

WM-10/WM-20
(1) General Precautions for Repair
1) There is. a safety switch built into the headphone jack, but it docs not operate unless the headphone
plug is plugged in.
2 ) When screwing in the control panel and audio board screws, be sure to insert a cassette tape first.
Reason : If pressure is applied to the tape transport ree] chassis, its plane is affected.
3) When performing repair which involves the removal of the function plate block or sleeve ass’y, be sure
to check shut-off for FWD.
4) In FF/REW mode, there is a rolling noise for about 3 seconds at tape end, then the motor stops. Check
by referring to the power changes below.
5) Do not reuse the capstan bush after having removed it.
6) By removing the audio board from the set and touching. 33(13-1 (Power OM) the motor will rotate without
pushing the FWD button (belt is on).
There will be a clicking noise, but this is not a defect, and will stop when the FWD button is pushed.
?) Defective soldering, pattern cuts, parts touching, etc. are not included under “Defective Parts" and
“Defective Locations", but be sure to check these also.
— 2 —

WM-10 WM-20
• No Operation
* Noise when battery is worn out {less than 0,9V)
• Mo Operation
Cause
Defective Location
Battery worn out
Battery terminal plate dirty.
Clean terminal plate (Daifron solvent)
Dirty leaf switch contact point.
S303-3 contact point cleaning (Daifron solvent)
flattery short: battery + terminal and audio board ground
touched.
Stick insulation on audio board.
Short of function plate ass’y mounting screw tip and
audio hoard pattern.
Stick insulation on audio board.
contact laaf
audio hoard
insulation
* Noise when battery is worn out
Operation: When{§}becomes 1.0V, 040! goes off, Q3G1 turns on, grounds lC3Q3(3)and reduces buzz noise.
— 3 —

WM-10/WM-20
No Power
LED does not light up
No converter operation
Converter Board Simple Check Method
• No Power
[f the battery LED lights up and reel table rotates when the headphone plug is plugged into the headphone
jack and PLAY button is pressed, OK.
headphone jack
VOLUME
BATTERY LED
PLAY button
STOP button
M button
►► button
No operation when headphone plug is plugged into head- Defective Part
phone jack and FLAY button is pressed. -
J401 p £303-3
* LED does not light up
Voltage, Waveform Defective Farts
Notes
reverse voltage
D40I, R401 - R4Q3
Q40I, Li, La, Ls open
flexible board
D3Q2 short
This LED (D40I) uses motor reverse voltage, so
does- not light up if the motor does not rotate.
Lights up at 2,5V
I
- 4 -

WM-10 WM-20
• No converter operation
Operation:
1.5V is first made AC, raised to 3.0V, then DC 3.0V
is obtained. Frequency approx. lOQkHz.
* Converter Board Simple Check Method
When the converter board is on the servo board (A),
check for 3 V between @ and ® .
When the converter hoard is by itself, solder on a 1,5kO
resistor as shown in the figure below and check for 3V
between ® and ® .
[CONVERTER BOARD]
0001 ZSBS24-BV3
[ CONVERTER BOARD I
Voltage check location
Transistor Section
Tr name open
short
between
E—C
short
between
E-B
Q801
ov 3,0 V OV
Q802
ov
0,4 V
Q803 ov
ov 0,4 V
Q804 ov
ov ov
Q805 7V
0.5V 4,2V
0617
OV 3.0V
ov
D801 7V OV
1 pa*En o*
... omz 2SCISS3 QBDS 25CI6Z3
HECT|P|£E VOLTAGE SE&
' ” i
1
I ov-
-tTiieo*
Q803
25D&*6-3-'
SWIM-HI Hi.
oeo k
RD4..3H-02 '
GB02
DftOI
imi TV
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0ft“4
ftflfU I X-ISPlH ,, v .
SW f T AJC04T 11 “
I_1 av-
kp
r * k
r*H0?
470fc
*4 LBV
'mJT
*T
-C&0J
' KLfflV
iFl
■ W w
rfi
€
J i
t
Resistor, Transformer Section
R, T name
open
R801, R803, R804,
R63S, R639, TSOI
OV
measured when each Tr is removed.
- 5 -

WM-10/WM-20
[* Motor does not stop tor FF/REW STOP^
Cause
Defective Parts
Effective rotation switch (S901) contact point.
Auto off circuit structural parts
Flexible board pattern open
S9G1, R634 - R63 9. C603 - C605
Q615, Q616, Q617
flexible- board
— 6 —

icaflj ex-zoos?
WM-10WM-20
* No Muting
• No Sound (FWD, but no sound)
• Low level
* No Dolby
• Hum Noise during Playback
Noise on L-CH
* No Muting
Operation:
Mutes dick noise immediately after power
on at power IC (1C3Q3) pin (Rj
During FF/REWj 1C303 pin (T) becomes
0.2V and muting is applied.
IC3Q3 pin @
Voltage, Waveform
Defective Parts
1
FV,
H
i muted
vtr ON
Q3G2, R3G7, R3G8
C3G6,ICS03
* No Sound (FWD, but no sound!
Cause
Remedy
Head lead open, defective head contact.
Check head lead, head position.
Jf leaf switch $303-2 {FF/REW) is on, muting is applied.
Move audio board in direction of the arrow to change
FF/REW switch contact point.
Defective preamp LC (IC301), Dolby iC (1C302). power IC
(1C303), circuit structural parts, or audio volume defective.
Check IC301, IC302,1C303,
Circuit parts, audio volume
Defective contact point because of ground piate solder
on rear of audio board.
Check ground plate solder. (8 locations)
No playback Level.
*Sce next page '‘Level".
— 7 —

W-20 WM-10WM-20
acra-i
Oiii’
Wistl
* Conditions
DOLBY: OFF
TYPE: NORMAL
standard tape: P4-L&I
Headphone connected
HEAD IN
PRE AMP
DOLBY OUT
1C301 L®
IC301 R®
IC301 L®
1C30X Ft®
1C302 L®
IC3G2 R®
j linVp'p
J SOmVp-p
1 llQmVp-p
Adjust so that VR OUT is 60mVp-p.
POWER AMPrC303 L®
INPUT IC305
HEADPHONE OUT
6QmVp-p
700mV[>-p
* Low Level
Cause
Defective Locations
Dolby (PB) level off
Adjust variable resistors (RV1GI „ 201) so that sound volume entrance is
—27„7dBs :t|dB when standard tape is played back.
27.7dBs actual value
0.028V - 0.036V
Measure by VTVM
±ldB P-P
79.2mVp-p ~ 102mVp-p
Measure by oscilloscope
• No Dolby
Cause Defective Parts
Dolby circuit
Dolby adjustment also should be checked
ICS 02
S3 02
R302
L-CH ,
Rill, R106 ~ Rl09 h C104 "-CI09
R-CH R211, R2G6 ~ R209, C2G4 ~ C2G9
• Hum Noise during Playback
Cause
Remedy
Generated when battery voltage is down.
Replace batteries.
Defective soldering on flexible board next to
Q302 (GND pattern) and GRY lead (for GND).
Repair soldering on flexible board and GRY lead.
• Noise on L-CH
Cause
Defective Location
Rotation switch (S9G1) noise goes onto head Change head lead IC30P
lead.
positioning. 0\uvvt
CD
Press white, red, 41 JX JL VmtT
5
■ L-J
yellow leads in white red,/ hIKC
o
the direction of _.-y^L->
the arrow, yellow
f j -
push bead lead
— 8 —

WM-10/WM-20 WM-1
* No Motor Rotation
* Motor Coil Check Method
* Fast, Stow Speed
* No Speed Acceleration
* Servo Board f A) (B| Simple Check Method
* No Motor Rotation
• Starting Circuit Operation
Q6 05
Goes on by motor reverse
voltage at (lie same time as
motor rotation.
_d
d
YES
Tape inns
Staw speed,
Rotates inti
* Feedba
Motet can
is appioxi
pins © „
Tape runs a
Tends to pi
Slightly fall
Ro Laticxn dr
* Motor Coil Check Method
A. Hail element between (JJ) - @ "i normai value
between ©-(g) j 240 £ 2 - 55 0 £2
b. coil check between ® - © \ normal vlaue
between (f) _ (g) j approx. 1J2
- 9 —

WM-T O WM-20
uit Operation
* Drive Circuit Operation
C607 Q603 0*06 Q604 Rotation
if reverse
ie time as
charging
OFF OFF OFF high speed relation
charging completed ON ON ON Servo applied
Symptoms Defective Parts
Tape Huns aWay. Q6Q3, Q6041 open
j short
Q6D5, Q606J between E-U
short open
C6G7
R6I0
R620
€607
€608
Stow speed, uneven rotation
0*04 short between E-C
Rotates intermittently
R6U I
FLV60! j " PGn
* Feedback Circuit Operation
Motor cannot rotate if there is no voltage here. Check that there
is approximately 0.6 V at C6G1 © . If not, check voltage at 10501
pins @ , (fi) , @ .
Symptoms. Defective Parts
Tape runs away
R*05 open
Q6 01, Q6 02 short be tween E €
Tends to run slow
0606 open
0*02 short between E—B
Slightly fast D601 open
Rotation uneven R&2.8 open
For no rotation, unsolder A phase (or 0 phase) to
make it open and rotate the motor by hand. If the
motor rotates at high speed only for B phase only,
B phase drive circuit is OK and A phase is defective.
Symptoms
Defective Parts
Slow speed
R*02, R6G&, R624
Q610, Q61), Q*| 2]
Q609,Q613 1
open
short
between E-C
Tape runs away
R&01, R6M open
• Fast, Slow Speed
FWD mode
Symptoms
Defective Parts
Fast speed R6I3, R614 \
(.TH601, R640) J 0pen
€612 short
Stow speed
R618 open
0*07 short between E-C
R.V601 hits control panel.
Slow speed, uneven
rotation
R615 open
I
- 1 0 -