VC-MH834 (serv.man3). 2 - Troubleshooting (35-58) - Sharp VCR Service Manual (repair manual)

vc-mh834 (serv.man3) service manual
Model
VC-MH834 (serv.man3)
Pages
24
Size
138.81 KB
Type
PDF
Document
Service Manual
Brand
Device
VCR / 2 - Troubleshooting (35-58)
File
vc-mh834-sm3.pdf
Date

Read Sharp VC-MH834 (serv.man3) Service Manual online

35
VC-M314HM
VC-MH834HM
1
0
1
1
 
1
10
1
1
1
1
1
0
1
0
0
0
1
0
1
0
0
0
1
0
0
0
0
0
1
0
0
0
1
0
1
0
0
0
1
0
S sensor
Open
Close
Mode detection inside
sensor A
1
1
1
0
0
0
0
0
0
Mode detection outside
sensor B
0
1
1
1
1
0
1
1
0
CS/EJ
ULD
PU1
PU2
VSR
PB
SLOW
FF
STOP
Cam graph E
25
20
15
10
5
0
60
120
180
240
300
380
G mechanical timing
Mode check
Cam mark 
Mode detection outside
(D709 SW B)
Mode detection inside
(D708 SW A)
0
19.812
81
179
233
200
265
282
316
334
10.354
12.812
CA/END
CS/EJ
UL
PU1
PU2
VSR
PB
SLOW
FF
STOP
Mode detection outside
Mode detection inside
S sensor
EJ
UL
PU
PU2
VSR
PB
SLW
FF
STP
0
1
1
0
1
1
0
0
0
0
0
1
0
0
1 or 0
Loading motor turns in reverse
direction and master cam
counterclockwise.
CASSETTE INSERTION     STOP
Cassette
inserting
Full-
loading
YES
YES
YES
NO
NO
NO
Unloading
Loading motor starts in normal
direction and master cam counter
clockwise.
Does mechanism position sw.
come off within 2.5 sec.?
Are start/end sensors at low level
before cassette insertion ?
Insert cassette.
Double action rack slides.
Drum motor starts.
Tape loading.
Pinch roller comes into contact.
Cam switch is at PB position.
Loading motor stop.
Is drum FG pulse outputted ?
End
End
Cassette is ejected and loading
motor stops.
Start sensor close.
(Cassette is judged
caught halfway.)
(Cassette LED or some other part
is judged defective.)
6. MECHANISM OPERA
TION FLOWCHART 
AND TROUBLESHOOTING GUIDE
MECHANISM OPERATION FLOWCHART
36
VC-M314HM
VC-MH834HM
STOP      REC/PLAY
PLAY     STILL
PLAY     VSR
VSR      PLAY
Capstan motor turns
counterclockwise.
Is take-up reel sensor signal
outputted ?
End
Press REC/PLAY key.
Picture appears.
Unloading
Set capstan motor to search
speed.
End
Press FF key.
PLAY      VSF
REC/PLAY      STOP
Capstan motor turns in
reverse direction.
Loading motor turns in
counterclockwise direction
and master cam clockwise.
Slow brake comes into
contact with capstan motor.
Slow brake
pressing
Cam switch is at STILL
position.
End
Capstan motor stops.
Press STOP key.
Loading motor stops.
End
Stop capstan motor.
NO
YES
Press STILL key.
Pinch
roller
releasing
Idler
swinging
Pinch
roller
pressing
Loading motor turns
clockwise and master
cam counterclockwise.
Turn capstan motor in
reverse direction.
Turn loading motor
counterclockwise.
Cam switch is at VSR
position.
Set capstan motor to search
speed.
Is take-up reel sensor signal
outputted ?
Press REW key.
Release pinch roller.
Cam switch is at PU2 position.
Cam switch is at PU1 position.
Stop loading motor.
Press pinch roller.
Loading motor turns clockwise.
Release the supply auxiliary 
brake.
Stop loading motor.
End
Unloading
Cam switch is at PB position.
End
Press PLAY Key.
Loading motor turns counter-
clockwise and master cam
clockwise.
Capstan motor turns
counterclockwise. PB speed.
NO
YES
37
VC-M314HM
VC-MH834HM
STOP      FF/REW
STOP      CASSETTE EJECT
FF/REW      STOP
NO
NO
FF/REW
operation
Brake
function
Turn capstan motor in
normal or reverse direction,
after the remaining tape has
been detected.
Loading motor turns counter-
clockwise.
Cam switcn is at Stop
position.
End
Press STOP key.
Press FF/REW key.
Stop capstan motor.
Loading motor stops.
End
Loading motor turns in clockwise and master cam
counterclockwise.
4 supply reel pulses
outputted ?
Does the take-up
reel pulse output
two edges?
Capstan motor turns
clockwise.
Loading motor turns
clockwise.
Cam switch is at
Eject position.
Loading motor
stops.
Capstan motor
stops.
Press EJECT key.
Tape
unloading
Cassette
eject
End
Capstan motor turns
clockwise.
Capstan motor turns
counterclockwise in about
2 seconds.
Stop loading motor.
Capstan motor turns in reverse direction.
Cam switch is at UL position.
YES
YES
38
VC-M314HM
VC-MH834HM
MECHANISM TROUBLESHOOTING
1. FF/REW FAILURE (NO TAPE WINDING)
Press FF key.
NO
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
Is master cam at
FF position ?
Does loading
motor operate?
Modes changing
smoothly through
cam switch ?
Loading motor
control system
in trouble.
Are Vco 12V and
Vcc 5V applied ?
Replace the
capstan motor.
Replace the idler
ass’y.
Replace the reel
sensor.
Is voltage applied
to loading motor ?
Loading motor is
damaged. Replace
it.
Voltage supply
system in trouble.
Mode sensor
system in trouble
or master cam
malpositioned.
Voltage supply
system in trouble.
Does capstan
motor turn in FF (or
REW) direction ?
Are idler wheel
ass’y and reel disk
in mesh ?
Is the pulse
outputted from reel
sensor ?
The cassette tape
is presumably
damaged.
2. REC/PLAY FAILURE (MODE RELEASE)
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
Is the master cam
at PB position ?
Does loading
motor operate ?
Modes changing
smoothly through
cam switch ?
Loading motor
control system
in trouble.
Are Vco 12V and
Vcc 5V applied ?
Replace the
capstan motor.
Replace the idler
ass’y.
Replace the reel
sensor.
Is voltage applied
to loading motor ?
Loading motor is
damaged. Replace
it.
Voltage supply
system in trouble.
Voltage supply
system in trouble.
Does capstan
motor turn ?
Are idler wheel
ass'y and reel disk
in mesh ?
Is the pulse 
outputted from reel
sensor ?
Check main PWB.
Page of 24
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Here you can read online and download Sharp VC-MH834 (serv.man3) Service Manual in PDF. VC-MH834 (serv.man3) service manual will guide through the process and help you recover, restore, fix, disassemble and repair Sharp VC-MH834 (serv.man3) VCR. Information contained in service manuals typically includes schematics / circuit diagrams, wiring diagrams, block diagrams, printed wiring boards, exploded views, parts list, disassembly / assembly, pcb.