Sharp VC-MH85 (serv.man4) Service Manual ▷ View online
43
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
NO
NO
NO
FLOW CHART NO.10 CASSETTE CONTROL TROUBLESHOOTING(2)
A cassette tape is taken in, but ejected at once.
Does the start sensor pulse at pin (87)
of IC701 change from "L" to "H" level
when the cassette tape is loaded?
of IC701 change from "L" to "H" level
when the cassette tape is loaded?
Check line between start sensor and pin
(87) of IC701.
(87) of IC701.
Does the end sensor pulse at pin (86)
of IC701 change from "L" to "H" level
when the cassette tape is loaded?
of IC701 change from "L" to "H" level
when the cassette tape is loaded?
Check line between end sensor and pin
(86) of IC701.
(86) of IC701.
Does the master cam mode shifter
operate normally when the cassette
tape is loaded?
operate normally when the cassette
tape is loaded?
Check line between cam switch and
IC701.
IC701.
Replace IC701.
YES
YES
YES
FLOW CHART NO.11 LOADING MOTOR AND EJECT TROUBLESHOOTING
The cassette tape fails to come out.
Does the capstan motor start when the
EJECT button is pressed?
EJECT button is pressed?
See FLOW CHART NO.12. CAPSTAN
MOTOR TROUBLESHOOTING
MOTOR TROUBLESHOOTING
Does the take-up reel disk turn when the
capstan motor is running?
capstan motor is running?
Check line between take-up reel
sensor and pin(2) of IC701.
sensor and pin(2) of IC701.
Is a "H" level applied at pin(10) of P701
when a reel pulse has been inputted?
when a reel pulse has been inputted?
Check line between pin(92) of IC701
and pin(10) of P701.
and pin(10) of P701.
Is the supply voltage of 12V fed to
pin(8) of P701?
pin(8) of P701?
Is the voltage about 10V sent out from
IC on mechanism?
IC on mechanism?
Check IC on mechanism.
Is the specified voltage applied at the
loading motor terminal?
loading motor terminal?
Check line between IC on mechanism
and loading motor.
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
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(29) of IC701?
DC given out of pin(29) of IC701?
Check IC701.
NO
NO
NO
NO
NO
YES
YES
YES
YES
Is the supply voltage of 5V fed to
pin(3) of P701?
pin(3) of P701?
Check PC 5V line.
Is the voltage more than 2.6V DC
sent in pin(9) of P701?
sent in pin(9) of P701?
Check line between pin(9) of P701
and pin(29) of IC701.
and pin(29) of IC701.
Is the voltage of pin(5) of P701 is
1.6~2.7V?
1.6~2.7V?
Check line between the pin(91) of
IC701 and pin(5) of P701.
IC701 and pin(5) of P701.
Is the supply voltage of 12V/20V fed
to pin(2) of P701?
to pin(2) of P701?
YES
Replace capstan motor.
Check MOTOR Vcc line and motor
voltage selector circuit.
voltage selector circuit.
44
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
FLOW CHART NO.14 DRUM MOTOR TROUBLESHOOTING(1)
The drum motor fails to run.
Is the voltage more than about 2.6V
DC given out of pin(30) of IC701?
DC given out of pin(30) of IC701?
Check IC701.
NO
NO
YES
Is the voltage more than about 2.6V
DC given out of pin(12) of P701?
DC given out of pin(12) of P701?
Check line between pin(30) of IC701
and pin(12) of P701.
and pin(12) of P701.
NO
YES
YES
Is the supply voltage of 12V fed to
pin(8) of P701?
pin(8) of P701?
Replace drum motor.
Check M 12V line.
FLOW CHART NO.15 DRUM MOTOR TROUBLESHOOTING(2)
The drum motor runs only for a few seconds.
Replace IC on mechanism.
Check peripheral circuit of IC on
mechanism
mechanism
Is drum PG signal given out from the
pin (11) of P701?
pin (11) of P701?
Is drum PG signal fed to pin(65) of
IC701?
IC701?
Check line between pin(11) of P701
and pin(65) of IC701.
and pin(65) of IC701.
Is head switching pulse sent out from
the pin(23) of IC701?
the pin(23) of IC701?
Check IC701.
Replace IC701.
NO
Check drum motor.
YES
YES
YES
YES
NO
NO
NO
D-FG
D-PG
YES
NO
YES
YES
NO
NO
FLOW CHART NO.16 HEAD SWITCHING PULSE TROUBLESHOOTING.
No head switching pulse.
See FLOW CHART NO.14, 15 (DRUM
MOTOR TROUBLESHOOTING(1), (2))
MOTOR TROUBLESHOOTING(1), (2))
Is the drum motor rotating?
Is the drum PG signal and drum FG
signal present at pin(65) of IC701?
signal present at pin(65) of IC701?
Replace IC701.
Check line between P701 and
IC701.
IC701.
Check peripheral circuit of IC on
mechanism.
mechanism.
Are the drum PG signal and drum FG
signal present on pin(11) of P701?
signal present on pin(11) of P701?
2.5V
2.5V
FLOW CHART NO.13 TIMER TROUBLESHOOTING
The LCD display fails to light up.
Is the supply voltage of 5V fed to
pin(37) of IC8001?
pin(37) of IC8001?
Check AT 5V line.
Is the supply voltage of 3.4V, 1.7V
feed to pin(38) and pin(39) of IC8001?
feed to pin(38) and pin(39) of IC8001?
Check pin(38), (39) of IC8001
and peripheral circuits.
and peripheral circuits.
Is it possible to confirm signals
LCD RESET, LCD CS, LCD CLOCK
and LCD DATA on the pins(36),
(42), (43) and (44) of IC8001?
LCD RESET, LCD CS, LCD CLOCK
and LCD DATA on the pins(36),
(42), (43) and (44) of IC8001?
Are the segment signals
supplied to the LCD display
(LC8001) fromthe driver IC
(IC8001)?
supplied to the LCD display
(LC8001) fromthe driver IC
(IC8001)?
Check peripheral circuit of pin(41)
of IC8001.
of IC8001.
Check that the LCD display is
free from damages such as
crack.
free from damages such as
crack.
Replace IC8001.
YES
YES
YES
YES
NO
NO
NO
NO
NO
Check the signal line between
IC701 and IC8001.
IC701 and IC8001.
YES
Is the OSC signal at pin(41) of
IC8001 present?
IC8001 present?
45
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
FLOW CHART NO.17 DRUM SERVO TROUBLESHOOTING
Drum servo does not function.
Check peripheral circuit of X701.
Is there 14.318MHz oscillation at
pins(37) and (38) of IC701?
pins(37) and (38) of IC701?
NO
In PB mode
YES
In REC mode
Is there drum FG signal at pin(65) of
IC701 present?
IC701 present?
Is the C-SYNC signal(reference) at pin
(50) of IC701?
(50) of IC701?
YES
NO
NO
Check peripheral circuit of pin(50) of
IC701, C716, C715 and R708.
IC701, C716, C715 and R708.
Check drum FG signal line.
Is the head switching pulse at pin (23) of
IC701 present?
IC701 present?
NO
See FLOW CHART NO.16
(HEAD SWITCHING PULSE TROUBLE-
SHOOTING.)
(HEAD SWITCHING PULSE TROUBLE-
SHOOTING.)
YES
YES
Is the drum APC output at pin (34) of
IC701 and drum AFC output at pin(32) of
IC701 present?
IC701 and drum AFC output at pin(32) of
IC701 present?
NO
Replace IC701.
YES
YES
Is the drum control voltage applied to
pin(12) of P701?
pin(12) of P701?
YES
Is pin(30) of IC701 in high impedance?
NO
YES
Check line between pins(34) and (32) of
IC701 and pin(12) of P701.
IC701 and pin(12) of P701.
Does the IC on mechanism operate
normally?
normally?
Replace IC701.
Replace drum motor.
NO
1
FLOW CHART NO.18 CAPSTAN SERVO TROUBLESHOOTING
Capstan servo does not function.
Only PB mode inoperative
YES
NO
Check "
1
"
Check capstan motor unit and/or replace.
Is there capstan AFC and APC signal at
pins(31) and (33) of IC701?
pins(31) and (33) of IC701?
Replace A/C head.
YES
NO
YES
NO
NO
YES
NO
Replace IC701.
NO
Is there REC CTL signal output at pins
(74) and (75) of IC701?
(74) and (75) of IC701?
Does PB CTL signal appear at pin (76) of
IC701?
IC701?
Does A/C head operate normally?
Adjust the height of the A/C head.
Check the capstan FG signal line between
pin(1) of P701 and pin(67) of IC701?
pin(1) of P701 and pin(67) of IC701?
Check peripheral circuit at pin(1) of P701.
Are REC and/or PB mode inoperative?
Check "
2
"
NO
YES
YES
Does pin(29) of IC701 operate normally?
NO
NO
Is there capstan APC signal at pin (33)
of IC701?
of IC701?
Does PB CTL signal appear at pin (76) of
IC701?
IC701?
Replace IC701.
2
Only REC mode inoperative
NO
Check peripheral circuit of pin(50) of
IC701, C716, C715 and R708.
IC701, C716, C715 and R708.
Is the C-SYNC signal(reference) at pin(50)
of IC701?
of IC701?
YES
YES
Does the capstan FG signal appear at pin
(67) of IC701?
(67) of IC701?
YES
NO
NO
Check peripheral circuit of X701.
Is there 14.318MHz oscillation at pins(37)
and (38) of IC701?
and (38) of IC701?
A
A
46
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
No picture E-E signal. (by pass)
Is picture signal input into the pins(31) and (32) of IC201?
YES
YES
YES
YES
NO
NO
NO
NO
NO
Check the line between pin(24) of TU101 and pin(31) of IC201.
Check the line between external video input terminal (J201) and
pin(31) of IC201.
Check the line betweem video input terminal and pin(28) of IC201.
Check the line between external video input terminal (J201) and
pin(31) of IC201.
Check the line betweem video input terminal and pin(28) of IC201.
Is picture signal outputted to the pin(52) of IC201?
Check the line between pins(63) and (62) of IC201
and all the way up thru to pins(84) and (85) of IC701.
and all the way up thru to pins(84) and (85) of IC701.
Is picture signal output to the emitter of video output buffer
(Q251)?
(Q251)?
1
Line output: Check video output buffer(Q251) peripheral and output terminal periphery.
2
RF output: Check video output buffer(Q251) peripheral and video input terminal of RF converter periphery.
Is supply voltage of 5V(Y-Vcc) fed to the pin(12) of IC201?
Check the PC 5V line.
Is there Y/C serial data and Y/C signal clock applied
to the pins(63) and (62) of IC201?
to the pins(63) and (62) of IC201?
Check peripheral circuit of Q251.
FLOW CHART NO.19 E-E MODE TROUBLESHOOTING