Sharp VC-MH705HM/LM User manual

1
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
VC-MH715HM
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
2st Edition
VIDEO CASSETTE RECORDER
SERVICE MANUAL
SHARP CORPORATION
In the interests of user-safety (Required by safety regulations in some
countries) the set should be restored to its original condition and only parts
identical to those specified be used.
VC-MH705HM/LM
VC-MH715HM
VC-MH815HM/LM
VC-MH85HM
VC-MH835HM
MODELS
CONTENTS
Page
1. SPECIFICATIONS................................................................................................................. 3
2. DISASSEMBLY AND REASSEMBLY ................................................................................... 4
3. FUNCTION OF MAJOR MECHANICAL PARTS................................................................... 7
4. ADJUSTMENT, REPLACEMENT AND ASSEMBLY OF MECHANICAL UNITS .................. 9
5. ELECTRICAL ADJUSTMENT ............................................................................................. 28
6. MECHANISM OPERATION FLOWCHART AND TROUBLESHOOTING GUIDE .............. 35
7. TROUBLESHOOTING ........................................................................................................ 41
8. BLOCK DIAGRAM............................................................................................................... 56
9. SCHEMATIC DIAGRAM AND PWB FOIL PATTERN ......................................................... 64
10. REPLACEMENT PARTS LIST ............................................................................................ 84
11. EXPLODED VIEW OF MECHANISM PARTS..................................................................... 93
12. PACKING OF THE SET .................................................................................................... 100
VC-MH835HM
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM PRECAUTIONS IN PART REPLACEMENT
When servicing the unit with power on, be careful to the section marked white all over.
This is the primary power circuit which is live.
When checking the soldering side in the tape travel mode, make sure first that the tape has been loaded and then turn
over the PWB with due care to the primary power circuit.
Makereadjustment,ifneededafterreplacementofpart,withthemechanismanditsPWBinpositioninthemainframe.
(1) Start and end sensors: Q701 and Q702
Insert the sensor’s projection deep into the upper hole of the holder. Referring to the PWB, fix the sensors tight
enough.
(2) Photocoupler: IC901 and IC902
Refer to the symbol on the PWB and the anode marking of the part.
(3) Cam switches A and B: S704
Adjust the notch of the part to the white marker of the symbol on the PWB. Do not allow any looseness.
(4) Take-up and supply sensors: D706 and D707.
Be careful not to confuse the setting direction of the parts in reference to the symbols on the PWB. Do not allow
any looseness.
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
1. SPECIFICATIONS
Format: VHS PAL standard
Video recording system: Two rotary heads, helical scan system
Video signal: PAL colour and I signals, 625 lines
Recording/playing time: 240 min max. with SHARP E-240 tape (SP mode)
480 min max. with SHARP E-240 tape (LP mode)
720 min max. with SHARP E-240 tape (EP mode)
Tape width: 12.7mm
Tape speed: 23.39 mm/s (SP mode)
11.70 mm/s (LP mode)
7.80 mm/s (EP mode)
Antenna: 75 ohm unbalanced
Receiving channel: UHF Channel E21-E69
RF converter output signal: UHF Channel E21-E69 (Preset to CH E36)
Power requirement: AC230V ~ 240V, 50Hz
Power consumption: Approx. 14.1W (AC240V/50Hz) and 3W max. at standby mode
Operating temperature: 5°C to 40°C
Storage temperature: –20°C to 55°C
Weight: Approx. 2.5 kg (VC-MH705HM/LM,MH715HM)
Approx. 2.9 kg (VC-MH815HM/LM,MH835HM,MH85HM)
Dimensions: 360 mm (W) x 231.4 mm (D) x 92.5 mm (H) (VC-MH705HM/LM)
360 mm (W) x 229.0 mm (D) x 92.0 mm (H) (VC-MH715HM)
430mm(W)x227mm(D)x92mm(H)(VC-MH815HM/LM,MH835HM,MH85HM)
VIDEO
Input: 1.0 Vp-p, 75 ohm
Output: 1.0 Vp-p, 75 ohm
S/N ratio: 45 dB (SP mode)
Horizontal resolution: 250 lines (SP mode)
AUDIO 0 dBs = 0.775 Vrms
Input: Line1: -3.8 dBs, 10k ohm
Line 2:-3.8 dBs, 10k ohm
Line 3:-3.8 dBs, 47k ohm
Output: Line1: -3.8 dBs, 1k ohm
Line 2:-3.8dBs, 1k ohm
S/N ratio: 46 dB
Frequency responce: 80 Hz ~ 10 kHz (SP mode)
80HZ ~ 5 kHz (LP mode)
Hi-Fi Dynamic Range: 90 dB TYP
Hi-Fi Wow and Flutter: 0.005%
Hi-Fi Frequency Responce: 20 Hz ~ 20 kHz
Hi-Fi Distortion: 0.5% max.
Hi-Fi Crosstalk (at 1kHz): 55 dB min.
Accessories included: 75 ohm coaxial cable
Operation manual
Infrared remote control
Battery
Quick Start Guide (QSG) (For VC-M705HM and VC-MH85HM)
Note: The antenna must correspond to the new standard DIN 45325
(IEC 169 - 2) for combined UHF/VHF antenna with 75 ohm connector.
Aspartofourpolicyofcontinuousimprovement,wereservethe
right to alter design and specifications without notice.
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4
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
8
A
D
7
7
9
1
C
242
4
5
B
E
B
D
A
C
6
D
VC-MH715HM
FRONT PANEL
B
3
3
VC-MH705HM/LM
FRONT PANEL
B
3
3
6
E
TOP CABINET
TOP CABINET 
FIX ANGLE
MAIN FRAME
OPERATION PWB
ANTENNA 
TERMINAL
COVER
EUR-TERM PWB
MAIN PWB
MECHANISM
CHASSIS
CASSETTE

HOUSING
CONTROL
F
F
2. DISASSEMBLY AND REASSEMBLY
2-1 DISASSEMBLY OF MAJOR BLOCKS
(VC-MH705HM/LM,MH715HM)
TOP CABINET :Remove 2 screws 1.
FRONT PANEL :Remove 2 screws 2and 7 clips 3.
MECHANISM/ :Remove 2 screw 4, 1 screw 5.
MAIN PWB Remove2screws6and2screws7
with antenna terminal cover. Remove
1 screw 9. Remove 1 screw 8 with
top cabinet fix angle.
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
(VC-MH815HM/LM,MH835HM,MH85HM)
1
10
5
8
A
A
1
C
C
E4
DA
B
D
A
B
7
6
29
Operation PWB
Main Frame
Cassette Housing Control
C
Top Cabinet
Front Panel 3
B
3
E
Mechanism
Chassis
Main PWB
(VC-MH835HM) (except VC-MH835HM)
VC-MH835HM only
8
F
F
TOP CABINET :Remove 4 screws 1.
FRONT PANEL :Remove 2 screws 2and 7 clips 3.
MECHANISM/ :Remove 1 screw 4, 1 screw 5,
MAIN PWB 1screw 0 and antenna terminal
cover. Remove 2 screws 6and
mechanismchassis.Remove1screw
7 and 2 screws 8with main PWB.
CASSETTE :Remove 2 screws 9.
HOUSING
CONTROL
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Pinch Drive Cam
Synchro Gear Master cam
Main Chassis
Drive Lever

2-2 CARES WHEN REASSEMBLING
INSTALLING THE CASSETTE HOUSING
When the cassette housing is installed on the mechanism,
the initial setting is essential condition.
Therearetwoinitialsettingmethods,namelyelectricaland
mechanical.
1. Electrical initial setting
So as to perform initial setting of mechanism execute the
Step1ofInstallationofcassettehousing.Afterascertaining
the return to the initial setting position install the cassette
housing. (Conditions: When mechanism and PWB have
been installed)
2. Mechanical initial setting
•Rotatethewormgearbypushingtheflangemanuallyuntil
return to initial position.
•When apply power supply to rotate the loading motor,
please remove/unsolder at least one terminal wire.
•If voltage applied to loading motor without diconnecting
the terminal wire, there is a possibility the capstan motor
IC will damage.
•The maximum applied voltage is 9V. If more than 9V,
there is apossibility the mechanism will damage.
•After ascertaining the return to the initial set position
installthecassettehousinginthespecifiedposition.(This
method is applied only for the mechanism.)
Rotate the flange of worm gear by using thin stick.
CW • • • Loading direction
CCW • • • Ejection direction
Note:
Be careful not to damage the gear of worm gear and

worm wheel gear. It miight cause a strange sound.
AH CONNECTOR
AE CONNECTOR
END SENSOR
END TIP SW
AA CONNECTOR
AD CONNECTOR
MODE SW
START SENSOR
VC-A50 only
AC CORD
90°
180°
270°
0°
MASTER CAM POSITION
This positioning hole
should be at front side.
INSTALLING THE MECHANISM ON PWB
Lower vertically the mechanism, paying attention to the
mechanism edge mode SW position, (Set the mode SW
position to 270° and make sure the master cam position
hole also in 270° position) and install the mechanism with
due care so that the parts are not damaged.
* Please make sure to insert correctly.
If not, strange moving will occur and will couse mecha-
nism damage.
PARTS WHICH NEED PARTICULAR CARE
When installing the mechanism chassis on the PWB unit,
take care so as to prevent deformation due to contact of
mechanism chassis with REC TIP SW.
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
3. FUNCTION OF MAJOR MECHANICAL PARTS (TOP VIEW)
No. Function No. Function
1Full erase head
2Supply pole base ass’y
3Tension arm
4Idler wheel ass’y
5Open guide
6Supply reel disk
7Supply main brake
8Take-up main brake
9Pinch drive cam
10 A/C head ass’y
11 Reverse guide lever ass’y
12 Reel relay gear
13 Take-up reel disk
14 Pinch roller lever ass’y
15 Drum ass'y
16 Loading motor block
17 Drum driver motor
18 Take-up pole base ass'y
26 Auto head cleaner Ass'y
(VC-MH815HM/LM,MH835HM)
17 15 26
11
5
9
14
12
8
16
13
4
6
2
7
3
1
18 10




VC-MH815HM/LM,MH835HM
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8
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
FUNCTION OF MAJOR MECHANICAL PARTS (BOTTOM VIEW)
No. Function No. Function
19 Syncro Gear
20 Master cam
21 Capstan D.D. motor
22 Reel belt
23 Clutch lever
24 Limiter pulley ass’y
25 Shifter
25
24
21
22
19
20
23




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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Figure 5-1.
5. ELECTRICAL ADJUSTMENT
Notes:
•Before the adjustment:
Electricaladjustments discussedhereare often requiredafterreplacement ofelectronic components and mechani-
cal parts such as video heads.
Check that the mechanism and all electric components are in good working condition prior to the adjustments,
otherwise adjustments can not be completed.
•Instruments required:
Colour TV monitor Dual-trace oscilloscope
Audio signal generator AC milli-voltmeter
Blank video cassette tape Alignment tape(VROCPSV)
Screwdriver for adjustment
Colour bar singnal generator
• Location of controls and test points
TP201
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Measuring
instrument
Mode
Cassette
Dual-trace oscilloscope
Colour TV monitor
Playback
Alignment tape
SERVO CIRCUIT ADJUSTMENT
ADJUSTMENTOFHEADSWITCHINGPOINT Measuring
instrument
Mode
Cassette
Colour TV monitor
Playback still
Self-recordedtape(SP/LP,EPmode)
(See Note below 1)
Control Tracking control buttons (+) or ( - )
Specification Noverticaljitterofpicture
ADJUSTMENT OF PAL SYSTEM FV (False
Vertical Sync) OF STILL PICTURE
Test point Pin(2) of TP201 (H.SW.P.) to CH-
1, VIDEO OUT jack to CH-2
(CH-1 trigger slope switch at (+),
Internal trigger at CH-1 side.)
Specification 6.5 ±0.5H (lines)
1. Remove the front panel and play the alignment tape.
2.GetTP801shortcircuitedorpresspress"TEST"key(47H)
at Universal remote control to call the test mode.
(LCD will blinking as tracking goes to center)
3. Press "PLAY" key.
Auto PG Mode will be ON and playback mark ">"
blinking.
4. Press "STOP" key
">" blinking stops and auto adjustment finished.
5. CheckthatV-Syncis6.5±0.5Handthewaveformisas
shown in Figure 5-2.
Note:
For manual PG Adjustment,press FF or REW key at
the Test Mode to set the tracking in center.
6.5 ±0.5H
V: 2V/div
CH-1
Head Switching Pulse
CH-2
Video signal
Figure 5-2.
Head Tape
2CBZF
2LP BBZG
4CBZF
4HiFi CBZF 1. Play a self-recorded tape.
2. Press the PAUSE/STILL button to freeze the picture.
3. Adjust (+) or ( - ) TRACKING buttons on the remote
control so that the vertical jitter of the picture is mini-
mized.
Note:
1Self-recorded tape is a cassette which program was
recorded by the unit being adjusted.
2The FV goes back to the it's initial state when the unit
is put into the system controller reset mode due to
power failure,etc.
In this case, preset the FV once again.
Y/C CIRCUIT ADJUSTMENT
CHECKING OF VIDEO E-E LEVEL
Measuring
instrument
Mode
Input signal
Oscilloscope
E-E or Record
EIA colour bar (1.0Vp-p)
Test point VIDEO OUT jack
Specification 1.0 ±0.2 Vp-p
1. Connect a 75 ohm terminating resistor to the VIDEO
OUT jack and connect an oscilloscope across this
termi-nating resistor.
(See Note below.)
2. Feed a colour bar signal to the VIDEO IN jack.
3. Make sure that the E-E signal amplitude is 1.0Vp-p as
shown in Figure 5-3.
Note:
If the 75 ohm terminating resistor is missing, the signal
amplitude will be doubled.
1.0 Vp-p
Figure 5-3.
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
1. Be sure that E-E level has been correctly specificed.
2. Connect a 75 ohm terminating resistor to the VIDEO
OUT jack and connect an oscilloscope across this
terminating resistor.(See Note below 1)
3. Play a self-recorded tape.
4. Make sure that the output signal amplitude is 1.0Vp-p
as shown in Figure 5-4.
Note:
1Ifthe75ohmterminatingresistorismissing,thesignal
amplitude will be doubled.
2Self-recorded tape is a tape which program was re-
corded by the unit being adjusted.
1.0 Vp-p
Figure 5-4.
CHECKING OF PLAYBACK LEVEL
Measuring Oscilloscope
instrument
Mode Record/Playback
Cassette Self-recorded tape
(See Note below 2)
Specification 1.0±0.2Vp-p
1. ConnectanACmilli-voltmetertotheAUDIOOUTjack.
2. Feed the audio signal shown in table to the AUDIO IN
jack.
3. Put the unit in E-E or recording mode.
4. Makesurethattheoutputlevelisvalueshownintable.
AUDIO CIRCUIT ADJUSTMENT
CHECKING OF E-E LEVEL
Measuring AC milli-voltmeter
instrument
Mode E-E/Record
Input signal 1kHz, –3.8 dBs
Test point AUDIO OUT jack
Specification –3.8 ±2dBs
1. ConnectanACmilli-voltmetertotheAUDIOOUTjack.
2. Feed the audio signal shown in table to the AUDIO IN
jack.
3. Make the self-recording and playback of the signal.
4. Makesurethattheoutputlevelisvalueshownintable.
CHECKING OF AUDIO RECORD LEVEL
Measuring AC milli-voltmeter
instrument
Mode Record/playback
Input signal 1kHz, –8.0 dBs
Test point AUDIO OUT jack
Specification –8.0 ±3dBs
CHECKING OF ERASE VOLTAGE AND OS-
CILLATION FREQUENCY
Measuring Oscilloscope
instrument
Mode Record
Test point Full erase head
Control T601
Specification 70 ±5kHz, 40Vp-p or greater
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31
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Observe the video output using the osiloscope and con-
firm as the above diagram
*V:200mV/div
H:20µsec/div
Measuring
instrument
Mode
Cassette
Spectrum
Analyzer
Record
Self-recorded tape
Test point YC CHIP Pin98
Specification 3.8MHz±50KHz
ADJUSTMENT OF FM Carrier Confirmation
VIDEO PAL Colour Bar(1Vp-p)
Measuring
instrument
Mode
Cassette
Osiloscope
Record
Self-recorded tape
(SP/EP mode)(See Note below)
Test point VIDEO OUT 21PIN or RCA Port
(75ΩTerminal)
Specification 1.0±0.2Vp-p
Y/C CIRCUIT ADJUSTMENT
ADJUSTMENT OF EE Level Confirmation
VIDEO PAL Colour Bar(1Vp-p)
Measuring
instrument
Mode
Cassette
Spectrum
Analyzer
Record
Self-recorded tape
Test point YC CHIP Pin98
Specification 4.8MHz±100KHz
ADJUSTMENT OF Deviation Confirmation
VIDEO Colour Bar(1Vp-p)
Measuring
instrument
Mode
Cassette
Osiloscope
Self-recorded/Playback tape
Test point YC CHIP Pin98
Specification about300mVp-p
ADJUSTMENT OF REC Current Confirma-
tion
VIDEO Colour Bar(1Vp-p)
1.0Vp-p
Record
<Diagram A>
Confirmthe Sinkchip is as the
left diagram <Diagram A>.
Sink Chip
3.80 4.80MHz
A
f
<Deviation>
Confirm the white peak frequency
follow the standard value.
(thedeviationbetweenshinkchipand
f white peak is 1MHz±100KHz)
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Measuring
instrument
Mode
Cassette
Osiloscope
Playback
Self-recorded/Playback tape
Test point VIDEO OUT port
(75Ωterminal)
Specification Check place 1.
(1±0.2Vp-p)
VIDEO Colour Bar
ADJUSTMENT OF PB Level Confirmation
Measuring
instrument
Mode
Cassette
Osiloscope
Recorded/Playback
Self-recorded/Playback tape
Test point VIDEO OUT
VIDEO mono-sco
ADJUSTMENT OF S-PICUTRE Confirmation
Measuring
instrument
Mode
Cassette
Voltmeter
EE
Optional
Test point AUDIO OUT
Specification -3.8±2dBs
VIDEO Optional
HIFI Audio Circuit ADJUSTMENT
ADJUSTMENTOFEELevelConfirmationHIFI
Lch, Rch
AUDIO AUDIO IN at 1KHz -3.8dBs
Measuring
instrument
Mode
Cassette
Voltmeter
Playback
Alignment Tape VRO-CBFF
Test point AUDIO OUT
Specification -3.8±2dBs
VIDEO Optional
ADJUSTMENTOFPBLevelConfrimationHIFI
Lch, Rch
AUDIO Optional
Measuring
instrument
Mode
Cassette
Voltmeter
Recorded/Playback
Self-recorded tape
Test point AUDIO OUT
Specification -3.8±2dBs
VIDEO Optional
ADJUSTMENTOFHIFILch,RchSelaRec/PB
Level Confirmation HIFI Lch, Rch
AUDIO AUDIO IN at 1KHz -3.8dBs
~Forthisitem,variablethetrackingswitch,andconfirm
the changing of the normal mode.
1.0Vp-p
Measure the picture out-
put port using the 75Ω
terminal Osiloscope and
confirmthediagramsame
as the left diagram.
~V:200mV/div
H:20µsec/div
Receive the mono-sco.
Confirmation : make sure no black split at the mono-sco
picuture during the self-Rec PB when the S-PICTURE is
ON with the S-PICTURE ON/OFF,make sure the pinture
level at the wedge part is change.
(S-PICUTRE ON - about 260 line)
(S-PICUTRE OFF about 240 line)
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
ADJUSTMENT OF LINE3(FRONT) INPUT
Level Confirmation HIFI Lch, Rch ADJUSTMENT OF Receive Image CH
Display eg:
JP : 0034300014
HEX CODE for Initial Jumper
YC : 34 340707
PAL PAL NTSC NTSC
SP LP/EP SP EP
VM : F8FB←Video Mode
NOR__ ←ROM Version
Mode EE
Measuring
instrument
Mode
Cassette
Voltmeter
EE
Self-recorded tape
Test point AUDIO OUT
Specification -3.8±2dBs
VIDEO Optional
AUDIO AUDIO IN at 1KHz -3.8dBs
Confirmthatthereisnonoiseandbeatinthereceiving strenght
and weakness electrics signal.
Measuring
instrument
Mode
Monitor Screen
EE
Specification <On Screen Display>
Jumper List
On Screen Display confirm Display
Reference
TIMER Circuit ADJUSTMENT
ADJUSTMENT OF Timer Initial JP and Y/C
Rec Current Confirmation
3. Afterconfirmation, Releasethe TESTcode (R/Ccode
47H), display will return to EE mode.
1. DuringEEmode,sendtheTESTCode(R/Ccode47H)
to VCR and hold the Test code, do not let go.
2. While sending the TEST code, the monitor screen will
display the initial JP and Y/C Rec Current setting,
Video mode and ROM Version condition.
Measuring
instrument
Mode
Digital Voltmeter
EE
Specification 2.5±0.5V
TUNER/IF Circuit ADJUSTMENT
ADJUSTMENT OF AFT Adjustment
Confirmation(except France)
Test point TU101 pin23
E-12ch, Input level 70dBµ
While selecting channel input TEST MODE(press once
on TEST KEY R/C) and select E-12ch.
(Just Tuning)
Adjustment
HM I40ch
LM I-Jch
ADJUSTMENT OF AFT Adjustment Confir-
mation (France)
F-10ch, Input level 70dBµ
While selecting channel input TEST MODE(press once
on TEST KEY R/C) and select F-10ch.
(Just Tuning)
F-4ch, Input level 70dBµ
While selecting channel input TEST MODE(press once
on TEST KEY R/C) and select F-4ch.
(Just Tuning)
Measuring
instrument
Mode
Digital Voltmeter
EE
Specification 2.5±0.5V
Test point TU101 pin23
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VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Power Circuit ADJUSTMENT
ADJUSTMENT OF Output Voltage Confirm
Measuring
instrument
Mode
Fix Load
Power Consumption device
Power off
actual load
Test point AC Plug
Specification 3.0W MAX
Item Test point Specification Fix Load
AT 12V AT between 12Vline~GND DC 12.5V±0.3V 360mA+actual load
AT 5V AT between 5Vline~GND DC 5.25V±0.1V 18mA+actual load
AT 39V AT between 39Vline~GND DC 39.0V±2.0V actual load
AT 25.0V AT between 25.5Vline~GND DC 26.0V±0.5V actual load
Measuring
instrument Digital Voltmeter
<Setting Condition>
1. Power Supply : AC190V(50Hz)
2. SURROUND temperature Setting : 20ºC±10ºC
3. load connect place : between AT 5V→AC connector
8PIN~AC connector1PIN
(High speed) : between AT25.5V→AC5PIN~AC2PIN
(Other model) : between AT12V→AC5PIN~AC2PIN
ADJUSTMENT OF Over Load Characteristic
Confirmation
Item Test point Specification Fix Load
AT 12V AT between 12Vline~GND Output above 11.0V 2.0~2.2A(over load)
AT 25.0V AT between 25.5Vline~GND Output above 25.0V
Measuring
instrument Osiloscope
when apply the over load at the AT12V/AT25.5V output for
every170msec,confirmthattheoutputis11.0V/25.0Vforevery
time.
70 100
2.2A
0.65A
(A)
(msec)
ADJUSTMENTOFPowerConsumptionCon-
firmation
1.Power supply : AC230V(50Hz)
2.Surround Temperature Setting : 20ºC±10ºC
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35
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Loading motor turns in reverse
direction and master cam
clockwise.
CASSETTE INSERTION STOP
Cassette
inserting
Full-
loading
YES
YES
YES
NO
NO
Loading motor starts in forward
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.
Drum motor starts.
Tape loading.
Pinch roller comes into contact.
Mode switch is at PB position.
Loading motor stop.
NO
Unloading
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 OPERATION FLOWCHART AND TROUBLESHOOTING GUIDE
MECHANISM OPERATION FLOWCHART
* This flowchart describes the outline of the mechanism’s operation, but does not give its details.
1
0
1
1
1
1
1
1
1
1
1
0
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
1
1
1
0
0
0
0
0
0
0
1
1
1
1
0
1
1
0
CS/EJ
ULD
PU1
PU2
VSR
PB
SLOW
FF
STOP
Code 1
Code 2
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
Code 1
(Mode SW/outside)
Code 2
(Mode SW/inside)
Mecha Mode
60
0 120 180 240 300 360
Mecha Mode
Mode check
Cam mark
Code 1
(Mode SW/outside)
Code 2
(Mode SW/inside)
CS/EJ UL PU1 PU2 VSR
PB STILL
SLOW REW
FF STOP
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36
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
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
forward direction and master 
cam CCW.
Slow brake comes into
contact with capstan motor.
Slow brake
pressing
Mode 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 reverse
direction and master cam 
clockwise.
Turn capstan motor in
reverse direction.
Turn loading motor forward 
direction.
Mode switch is at VSR
position.
Set capstan motor to search
speed.
Is take-up reel sensor signal
outputted ?
Press REW key.
Release pinch roller.
Mode switch is at PU2 position.
Mode switch is at PU1 position.
Stop loading motor.
Press pinch roller.
Loading motor turns reverse
direction
Release the supply main 
brake.
Stop loading motor.
End
Unloading
Mode switch is at PB position.
End
Press PLAY Key.
Loading motor turns forward
direction and master cam
CCW.
Capstan motor turns
counterclockwise. PB speed.
NO
YES

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37
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
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 forward
direction.
Mode switch is at Stop
position.
End
Press STOP key.
Press FF/REW key.
Stop capstan motor.
Mode SW is at FF/REW 
position.
Loading motor rotate forward.
Loading Motor stop rotate.
Mode SW at PB position.
Loading motor reverse direction.
Loading Motor stop rotate.
Loading motor stops.

End
Loading motor turns in reverse direction and master cam
clockwise.
4 supply reel pulses
outputted ?
Does the take-up
reel pulse output
two edges ?
Capstan motor turns
clockwise.
Loading motor turns
reverse direction.
Mode 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.
Mode switch is at UL position.
YES
YES

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38
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
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
mode switch ?
Loading motor
control system
in trouble.
Are Vco 24V 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 SW 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
mode switch ?
Loading motor
control system
in trouble.
Are Vco 24V 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.


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Digitized in Heiloo the Netherlands
Not for sale!

39
VC-MH705HM/LM
VC-MH815HM/LM,MH85HM
VC-MH715HM,MH835HM
Replace loading motor block.
3. WINDING FAILURE AT VSR 4. UNUSUAL SOUND IN EACH MODE
Is Playback
function normal ?
Master cam
shifting to VSR
position ?
Go to 2. REC/
PLAY FAILURE
routine.
Replace idler
gear ass’y.
Replace limiter
pulley ass’y.
Replace reel
sensor.
Go to 2. REC/
PLAY FAILURE
routine.
Are idler wheel
ass’y and supply
reel disk in mesh ?
Is supply reel disk
winding torque
normal ?
Is pulse outputted
from reel sensor ?
Check main PWB.
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
YES
YES
NO
NO
YES
Press REW key.
4-i) Unusual sound in cassette
insertion and ejection mode
Is unusal sound heard during
cassette control running ?
Unusual sound heard with pinch
roller lever going up or down ?
Is unusual sound heard during
loading/unloading ?
Check pinch drive cam, pinch roller ass'y
and reverse guide for their actions.
Replace damaged one with new one.
Replace cassette control ass’y.

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Digitized in Heiloo the Netherlands
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