Sharp VC-M314 (serv.man8) Service Manual ▷ View online
41
VC-M314HM
VC-MH834HM
VC-MH834HM
7. ELECTRICAL
TROUBLESHOOTING
FLOW CHART NO.1 POWER TROUBLESHOOTING(1)
No power
Unplug the
AC power cord.
Replug it a few minutes later
.
See FLOW CHAR
T
NO.2 POWER
TROUBLESHOOTING(2)
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
Is the fuse good?
Replace fuse.
Is
A
T
5V voltage line normal?
Check primary circuit.
Are A
T
42V
, A
T
23V
, A
T
12.6V
,
and filament voltage lines normal?
Check each rectifier circuits and
short-circuit of secondary circuit.
Is "H" level applied at pin(1) of
IC701?
Check peripheral circuits Q9603
and P-F
AIL
(L) signal line etc.
Check system control circuit
(IC701).
FLOW CHART NO.3 POWER TROUBLESHOOTING(3)
In case of abnormal noise(sound)
Check D9603, D9604, D9605
and D9606.
The D9603, D9604, D9605 and
D9606 as a result of check
if poor the replace.
NO
FLOW CHART NO.2 POWER TROUBLESHOOTING(2)
In case of Fuse(F901) blown out.
Replace F901, Q901 and R904,
check D910, D91
1, D912 and
D913 as aresult of check, if poor
,
replace at the same time.
Check short-circuit or leak of
D9603, D9604, D9605, D9606
and secondary circuit.
FLOW CHART NO.5 TIMER TROUBLESHOOTING (1)
The LCD display fails to light up.
Is the supply voltage of 5V fed to
pin(37) of IC8001?
Check STBY
5V line.
Is the supply voltage of 3.4V
, 1.7V
feed to pin(38) and pin(39) of IC8001?
Check pin(38), (39) of IC8001
and peripheral circuits.
Is it possible to confirm signals
LCD RESET
, LCD CS, LCD CLOCK
and LCD DA
T
A
on the pins(36),
(42), (43) and (44) of IC8001?
Are the segment signals
supplied to the LCD display
(LC8001) fromthe driver IC
(IC8001)?
Check peripheral circuit of pin(41)
of IC8001.
Check that the LCD display is
free from damages such as
crack.
Replace IC8001.
YES
YES
YES
YES
NO
NO
NO
NO
NO
YES
YES
YES
NO
NO
NO
FLOW CHART NO.4 POWER TROUBLESHOOTING(4)
In case of output voltage at low level.
Check peripheral circuits IC901,
IC9601, C9613, R9608, R9609,
R9610 and R961
1.
The IC901, IC9601, C9613, R9608,
R9609, R9610 and R961
1 as a result
of check, if poor the replace.
Check IC901 and peripheral
circuits.
Replace Q902.
Check short-circuit or leak of
T901.
Replace T901.
Check primary circuit and peripheral
circuit of Q901 and Q902.
Check the signal line between
IC701 and IC8001.
YES
IC8001 present?
Is the OSC signal at pin(41) of
42
VC-M314HM
VC-MH834HM
VC-MH834HM
Is the cassette housing
distorted?
NO
YES
YES
YES
YES
NO
YES
NO
NO
YES
NO
YES
FLOW CHART NO.8 CASSETTE CONTROL
TROUBLESHOOTING(1)
A
cassette tape is not take in.
NO
NO
Check start sensor cover
.
Check line between start sensor
and pin(79) of IC701.
Check line between pin(93) of
IC701 and pin(1
1) of IC7002.
Is the supply voltage of 12V fed
to pin(9) of IC7002?
Check M 12V lines.
Check IC7002.
Check line between IC7002 and
loading motor
.
Replace loading motor
.
Is the specified voltage applied
at the loading motor terminal
when the cassette tape is inserted?
Does pin(13) of IC7002 change to
about 10V when the cassette
tape in inserted?
Does pin(1
1) of IC7002 go to a
"H" level when the cassette tape
is inserted?
Does pin(79) of IC701 change
from "H" to "L" level when the
cassette tape is inserted?
Does the start sensor cover go
to open when the cassette tape
is inserted?
Does the key switch make good
contact, when the cassette tape is
inserted?
Check switch contact.
Is there the function control voltage
inputted at the pins(87) and (88) of
IC701, when the keys are activated?
Replace IC701.
Check peripheral circuit of pins(87) and
(88) of IC701, and the function keys.
YES
NO
NO
YES
Key-in input is not received
SWITC
FUNCTION
SWITC
FUNCTION
Ref No. Ref No.
NOP
NOP
5.000V
SW889
REW
P801
CASSETTE
4.279V
SW893
FF
NOP
3.694V
SW892
REC
SW817
SP/LP/EP
3.081V
SW894
PLA
Y
P802
TEST
2.561V
SW891
P
AUSE
SW816
CH+
1.864V
SW890
ST
OP
SW814
MENU
1.250V
SW810
SET
SW81
1
EJECT
0.625V
SW815
CH(-)
SW813
POWER
0.000V
KEY
-1 IN
KEY
-0 IN
TERMINAL
(Pin87 of IC701)
(Pin88 of IC701)
VOL
T
AGE
FLOW CHART NO.7 INFRARED R/C TROUBLESHOOTING
No operation is possible from the infrared remote control.
Dose the infrared remote control
function?
Replace infrared remote control
as required.
Is the supply voltage of 5V fed to
pin(3) of RMC831.
Check
A
T
5V and GND lines.
Is "L" pulse sent out from pin(1) of
the receiver when the infrared remote
control is activated?
Replace receiver
.
Check between at pin(1) of receiver
and all the way up thru to pin(5) of
IC701.
Replace IC701.
YES
NO
YES
NO
NO
NO
YES
A/D KEY
INPUT
SPECIFICA
TION:-
FLOW CHART NO.6 TIMER TROUBLESHOOTING (2)
Fix or replace the cassette
housing.
43
VC-M314HM
VC-MH834HM
VC-MH834HM
YES
YES
YES
NO
NO
NO
FLOW CHART NO.1
1 SYSTEM CONTROL
TROUBLESHOOTING
No power is turned on.
Does power control (H) signal at
pin(94) of IC701 change from "L" to
"H" level?
Check IC701.
Does the base voltage of Q9904 or
Q9951 change from about 12.6V to
11.8V?
Check line between Q9904 or
Q9951, Q9905 and IC701.
Is voltage of 12V sent out from the
emitter of Q9904 or Q9951 transistor?
Check peripheral circuit of Q9904
or Q9951 and
A
T
12V line.
YES
YES
YES
NO
NO
Does the base voltage of Q9903
change from about 5.5V to 6.2V?
Check line between emitter of Q9904
or Q9951 and base of Q9903.
Is voltage of 5V sent out from the
emitter of Q9903 transistor?
Check peripheral circuit of Q9903
and
A
T
5V line.
Check peripheral circuit for poor
soldering.
NO
NO
NO
FLOW CHART NO.9 CASSETTE CONTROL
TROUBLESHOOTING(2)
A
cassette tape is taken in, but ejected at once.
Does the start sensor pulse at pin(79)
of IC701 change from "L" to "H" level
when the cassette tape is loaded?
Check line between start sensor
and pin(79) of IC701.
Does the end sensor pulse at pin(85)
of IC701 change from "L" to "H" level
when the cassette tape is loaded?
Check line between end sensor
and pin(85) of IC701.
Does the master cam mode
shifter operate normally when the
cassette tape is loaded?
Check line between cam switch
and IC701.
Replace IC701.
YES
YES
YES
FLOW CHART NO.10 LOADING MOT
OR
AND EJECT TROUBLESHOOTING
The cassette tape fails to come out.
Does the capstan motor start when
the EJECT
button is pressed?
See FLOW CHAR
T
NO.12
CAPST
AN MOT
OR
TROUBLE-
SHOOTING
Does the take-up reel disk turn
when the capstan motor is running?
Check line between take-up reel
sensor and pin(2) of IC701.
Is a "H" level applied at pin(12)
of IC7002 when a reel pulse has
been inputted?
Check line between pin(92) of
IC701 and pin(12) of IC7002.
Is the supply voltage of 12V fed
to pin(9) of IC7002?
Is the voltage about 10V sent out
from pin(15) of IC7002?
Check IC7002.
Is the specified voltage applied at
the loading motor terminal?
Check line between IC7002 and
loading motor
.
Does the loading motor run?
Replace cassette cam, gear
, etc.
YES
YES
YES
Check M 12V lines.
NO
YES
NO
YES
YES
YES
NO
NO
NO
NO
NO
Replace loading motor
.
44
VC-M314HM
VC-MH834HM
VC-MH834HM
FLOW CHART NO.13 DRUM MOT
OR TROUBLESHOOTING(1)
The drum motor fails to run.
Is the voltage more than about 2.6V
DC given out of pin(58) of IC701?
Check IC701.
NO
NO
NO
YES
YES
Check PC 5V
.
Is the supply voltage of 5V fed to
pin(3) of IC7002?
Is the voltage more than about 2.6V
DC given out of pin(2) of IC7002?
Check line between pin(58) of
IC701 and pin(2) of IC7002.
NO
YES
YES
Is the supply voltage of 12V fed
to pin(21) of IC7002?
Replace drum motor
.
Check M 12V line.
FLOW CHART NO.12 CAPST
AN MOT
OR TROUBLESHOOTING
The capstan motor fails to run.
Is the voltage more than about 2.6V
DC given out of pin(59) of IC701?
Check IC701.
NO
NO
NO
NO
NO
YES
YES
YES
YES
Is the supply voltage of 5V fed to
pin(8) of
AC connector?
Check PC 5V line.
Is the voltage more than 2.6V DC
sent in pin(4) of
AC connector?
Check line between the
AC
connector and pin(59) of IC701?
Is the voltage of pin(3) of
AC
connector 1.6~2.7V?
Check line between the pin(60) of
IC701 and pin(3) of
AC connector
.
Is the supply voltage of 12V/25V fed
to pin(5) of
AC connector?
YES
Replace capstan motor
.
Check MOT
OR Vcc line and motor
voltage selector circuit.
(Q9507, Q9508, Q9904, Q9951)
FLOW CHART NO.14 DRUM MOT
OR TROUBLESHOOTING(2)
The drum motor runs only for a few seconds.
Replace IC7002.
Check peripheral circuit of pins
(4), (5), (6) and (7) of IC7002.
Is drum PG signal given out from
the pin(7) of IC7002?
Is drum PG signal fed to pin(66)
of IC701?
Check line between pin(7) of
IC7002 and pin(66) of IC701.
Is head switching pulse sent out
from the pin(23) of IC701?
Check IC701.
Replace IC701.
NO
Check drum motor
.
YES
YES
YES
YES
NO
NO
NO
D-FG
about 5Vp-p
D-PG
about 5Vp-p
YES
NO
YES
YES
NO
NO
FLOW CHART NO.15 HEAD SWITCHING PULSE TROUBLESHOOTING.
No head switching pulse.
See FLOW CHAR
T
NO.13, 14
(DRUM MOT
OR
TROUBLESHOOTING(1), (2))
Is the drum motor rotating?
Is the drum PG signal and drum
FG signal present on pins(66)
and (65) of IC701, respectively?
Replace IC701.
Check line between IC7002
and IC701.
Check peripheral circuit of
IC7002.
Are the drum PG signal and drum
FG signal present on pins (7), (8)
of IC7002?
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