VC-M303 (serv.man9). Electrical Trouble Shooting - Sharp VCR Service Manual (repair manual)

vc-m303 (serv.man9) service manual
Model
VC-M303 (serv.man9)
Pages
11
Size
64.42 KB
Type
PDF
Document
Service Manual
Brand
Device
VCR / Electrical Trouble Shooting
File
vc-m303-sm9.pdf
Date

Read Sharp VC-M303 (serv.man9) Service Manual online

38
7. ELECTRICAL
 TROUBLESHOOTING
FLOW CHART NO.3 POWER TROUBLESHOOTING(3)
In case of abnormal noise(sound)
Check D9612, D9601, D9602, 
D9603, D9604 and D9607.
The D9612, D9601, D9602, D9603, 
D9604 and D9607 as a result of 
check, if poor the replace.
NO
FLOW CHART NO.5 TIMER TROUBLESHOOTING (1)
The flourescent display tube fails light up.
Is the supply voltage of 5V fed to 
pin(18) of IC801?
Check STBY 5V line.
Is the supply negative voltage of 
-25V fed to pin(16) of IC801?
Check negative voltage line(STBY 
-25V) and power circuit.
Is there 4MHz oscillation at 
pins(19) and (20) of IC801?
Check FL801.
Is the filament voltage applied 
between (1)/(2) and (31)/(32) of the 
fluorescent display tube?  
Also negative voltage applied 
between these pins and GND.
Check power circuit and peripheral 
circuit of D9910.
Does the fluorescent display tube 
function?
Replace IC801.
Check for cracks on the fluorescent 
display tube.
YES
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 R9611.
The IC901, IC9601, C9613, R9608, 
R9609, R9610 and R9611 as a result 
of check, if poor the replace.
Check IC901 and peripheral circuits 
pin(9) of IC902.
Replace IC902.
Check short-circuit or leak of T901.
Replace T901.
Check primary circuit and peripheral 
circuit of Q901.
FLOW CHART NO.1 POWER TROUBLESHOOTING(1)
No power
Unplug the AC power cord.
Replug it a few minutes later.
See FLOW CHART NO.2 POWER 
TROUBLESHOOTING(2)
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
Is the fuse good?
Replace fuse.
Is AT 5V voltage line normal?
Check primary circuit.
Are AT 42V, AT 23V, AT 12.6V, AT -25V 
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-FAIL (L) signal line etc.
Check system control circuit(IC701).
FLOW CHART NO.2 POWER TROUBLESHOOTING(2)
In case of Fuse(F901) blown out.
Replace F901, Q901, IC902 and 
R904, check D910, D911, D912 and 
D913 as a result of check, if poor, 
replace at the same time.
Check short-circuit or leak of D9612, 
D9601, D9602, D9603, D9604, 
D9607 and secondary circuit.
39
CASSETTE
P803
TEST
P804
S809
MENU
S806
CH(+)
S811, 812
EJECT
S813
3.8V
SW 1/SW 2 INPUT VOLTAGE(V)
3.1V
2.5V
1.9V
1.2V
0.6V
POWER
S885
STOP
S884
PLAY
S883
PAUSE/STILL
S882
REC
S807
SET
S810
CH(-)
FLOW CHART NO.6 TIMER TROUBLESHOOTING (2)
Does the key switch make good 
contact, when the cassette tape is 
inserted?
Check switch contact.
Is there a short in the scan outs or 
key inputs?
Check all the terminals of IC801 
and switches for poor soldering.
Are pulses received at pins(26) thru 
(29) of IC801 when the keys are 
activated?
Check lines of key in and scan out.
Check IC801, IC701 and FIP data, 
FIP clock, FIP CS and key data.
YES
YES
NO
NO
NO
YES
Key-in input is not received
<For jog shuttle mode
.>
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
<Except for jog shuttle mode
.>
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 
C813 of (+) side?
Check AT 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
Is the cassette housing distorted?
Fix or replace the cassette housing.
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(11) of IC702.
Is the supply voltage of 12V fed to 
pin(13) of IC702?
Check M 12V  lines.
Check IC702.
Check line between IC702 and 
loading motor.
Replace loading motor.
Is the specified voltage applied at the 
loading motor terminal when the 
cassette tape is inserted?
Does pin(12) of IC702 change to 
about 10V when the cassette tape in 
inserted?
Does pin(11) of IC702 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?
40
FLOW CHART NO.10 LOADING MOTOR AND EJECT TROUBLESHOOTING
The cassette tape fails to come out.
Does the capstan motor start when 
the EJECT button is pressed?
See FLOW CHART NO.12 CAPSTAN 
MOTOR TROUBLESHOOTING
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(10) of 
IC702 when a reel pulse has been 
inputted?
Check line between pin(92) of IC701 
and pin(10) of IC702.
Is the supply voltage of 12V fed to 
pin(13) of IC702?
Is the voltage about 10V sent out 
from pin(15) of IC702?
Check IC702.
Is the specified voltage applied at the 
loading motor terminal?
Check line between IC702 and 
loading motor.
Does the loading motor run?
Replace loading motor.
Replace cassette cam, gear, etc.
YES
YES
YES
Check M 12V lines.
NO
YES
NO
YES
YES
YES
NO
NO
NO
NO
NO
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 he cassette 
tape is loaded?
Check line between cam switch and 
IC701.
Replace IC701.
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
FLOW CHART NO.11 SYSTEM CONTROL TROUBLESHOOTING
No power is turned on.
Are key data pulses applied at 
pin(15) of IC701, respectively?
Check IC801 and IC701, and all the 
way thru between them.
Are FIP data pulses, FIP clock pulses and FIP control ready pulses applied to pins(25), (24), 
(23) and (22) of IC801, respectively?
Does power control (H) signal at 
pin(94) of IC701 change from "L" to 
"H" level?
Check IC701.
Does the base voltage of Q9905 
change from about 9.3V to 10V?
Check line between Q9905, Q9906 
and IC701.
Is voltage of 9V sent out from the 
emitter of Q9905 transistor?
Check peripheral circuit of Q9905 
and AT 12.8V line.
YES
YES
YES
NO
NO
Does the base voltage of Q9908 
change from about 5.5V to 6.2V?
Check line between emitter of Q9905 
and base of Q9908.
Is voltage of 5V sent out from the 
emitter of Q9908 transistor?
Check peripheral circuit of Q9908 
and AT 5V line.
Check peripheral circuit for poor 
soldering.
41
FLOW CHART NO.12 CAPSTAN MOTOR 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/20V fed 
to pin(5) of AC connector?
YES
Replace capstan motor.
Check MOTOR Vcc line and motor 
voltage selector circuit.
(Q9903, 9904, 9909, 9910)
FLOW CHART NO.13 DRUM MOTOR 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 and line and pin(9) 
of IC701.
Is the supply voltage of 5V fed to 
pins(25) and (2) of IC702?
Is the voltage more than about 2.6V 
DC given out of pin(29) of IC702?
Check line between pin(58) of IC701 
and pin(29) of IC702.
NO
YES
YES
Is the supply voltage of 12V fed to 
pin(20) of IC702?
Replace drum motor.
Check M 12V line.
FLOW CHART NO.14 DRUM MOTOR TROUBLESHOOTING(2)
The drum motor runs only for a few seconds.
Replace IC702.
Check peripheral circuit of pins(4), 
(5), (6) and (7) of IC702. 
Is drum PG signal given out from the 
pin(8) of IC702?
Is drum PG signal fed to pin(66) of 
IC701?
Check line between pin(8) of IC702 
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 CHART NO.13, 14 
(DRUM MOTOR 
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 IC702 and 
IC701.
Check peripheral circuit of IC702.
Are the drum PG signal and drum 
FG signal present on pins (8), (9) 
of IC702?
Page of 11

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