DOWNLOAD Sharp VC-MH85 (serv.man12) Service Manual ↓ Size: 743.5 KB | Pages: 19 in PDF or view online for FREE

• Adjustment
1. If the indication of torque cassette meter is lower than

the setting, shift the tension spring engagement to the
part A.

2. If the indication of torque cassette meter is higher than

the setting, shift the tension spring engagement to the
part B.

• Setting
1. Switch from the FF mode to the STOP mode.
2. Disconnect the power cord.
3. Set a torque gauge to zero on the scale. Place it on the

take-up reel disk.

4. Please check Idler gear not contact with reel relay gear

(TU side)

• Checking
1. Turn the torque gauge at a rate of about one turn/2 sec

in the CCW direction/CW direction so that the reel disk
and torque gauge pointer rotates at equal speed and
make sure that the value is within the setting (CCW
direction: 4.41 

± 1

mN·m (45 

 ±  

gf·cm), CW direction:

4.12 

± 1.

mN·m (42 

to 

gf·cm).

2. Adjustment of the brake torque at the supply side and the

take-up side

• Unless the supply side brake torque or take-up side

brake torque is within the setting, clean the felt surface
of reel disk (supply, take-up) brake lever, check again
the brake torque.

• If value cannot be set within the setting yet, replace the

main brake ass'y or main brake spring.

• Setting
1. Set a torque gauge to zero on the scale. Place it on the

supply reel disk.

2. Switch from the FF mode to the STOP mode.
3. Disconnect the power cord.
4. Please check Idler gear not contact with reel relay gear

(SU side)

Tension arm

Tension spring

CW

CCW

CW

Supply reel disk

Torque gauge

Torque gauge

CCW

Take-up reel
disk

A

B

CCW: 4.41 

±

      mN

⋅

m (45 

±

      gf

⋅

cm)

CW:

4.12 

±

      mN

⋅

m (42 

±

       gf

⋅

cm)

Turn the torque gauge at a rate of about one turn/2 sec
in the CW direction/CCW direction with respect to the
supply reel disk so that the reel disk and torque gauge
pointer rotate at equal speed, and make sure that the
value is within the setting (CW direction: 4.12 ±      mN·m
(42     gf·cm); CCW direction: 4.41      mN·m (45  

15

gf·cm).

+15
–12

+2.0
–1.5

+20
–15

+1.5
–1.2

CCW: 4.41 

±

      mN

⋅

m (45 

±

      gf

⋅

cm)

CW:

4.12 

±

      mN

⋅

m (42 

±

       gf

⋅

cm)

+2.0
–1.5
+1.5
–1.2

+20
–15
+15
–12

+2.0
–1.5

+20
–15

+1.5
–1.2

+15
–12

+2.0
–1.5
+1.5
–1.2

+20
–15
+15
–12

• Replacement
1. Solder the removed PWB to the new head assembly.
2. Adjust the height from the A/C head arm (lower surface)

to the A/C head plate to 10.8mm with slide calipers. (3
places of azimuth screw section, tilt screw section and A/
C head front section) (See the figure below.)

3. Align the left end of gear of A/C head arm with the

punched mark of chassis, tentatively tighten the screws

1

  so as to ensure smooth motion of A/C head arm.

Tightening torque must be 0.45 ± 0.05N·m (4.5 ±
0.5kgf·cm).

1. In eject position unplug the power cord.

1. Take out FFC holder from main chassis.

(Push 3 hooking point and pull-up the
holder).

2. Remove the screws 

123

, Tilt screw.

3. Unsolder the PWB fitted to the A/C head.
Notes:
1. When replacing, never touch the head. If you touched,

clean with the cleaning liquid.

2. When removing the screw 

3

, take care so that the

spring may out.

Note:
1. If the screw 

1

  is tighten tentatively too loose, the

azimuth and height of A/C head may change when they
are finally tightened. Therefore care must be taken.

2. After completion of A/C head be sure to adjust tape

running. (Execute the running adjustment by the method
described in 4-17.)

Height screw

Left end of A/C head arm gear
Punched line mark on chassis

1

3

1

2

A/C head screw

Azimuth spring

Height adj. screw

A/C head PWB ass'y
(with A/E)

Tilt screw

Height Adj. spring

A/C head PWB

Azimuth adj. screw

*Derection designation.
(The bottom part is big.)

A/C head plate

10.8mm

A/C head FFC

A/C FFC holder

Solder

A/C head PWB

New A/C head ass'y

A/C head plate

*Fit the groove of FFC to
 the boss of the holder.

AC Head 
FFC
Holder

1. Tape run rough adjustment

1

Check and adjust the position of the tension pole.
(See 4-12.)

2

Check and adjust the video search rewind back
tension. (See 4-10.)

3

Connect the oscilloscope to the test point for PB ATR
signal output (TP201). Set the synchronism of the
oscilloscope to EXT. The PB ATR signal is to be
triggered by the head switching pulse (TP202).

4

Set the alignment tape (VROCPSV) to play.

5

Press the tracking button (+), (–) and change the
ATR signal waveform from max to min and from min
to max. At this time make sure that the ATR signal
waveform changes nearly parallel.

6

Unless the ATR signal waveform changes nearly
parallel, adjust the height of supply side and take-up
side guide roller so that the envelope waveform
changes nearly parallel. (For ATR signal adjustment
procedure refer to Figure 4-30.)

7

Turn the tilt screw to remove the tape crease at the
fixing guide flange.
Playback the tape and check for tape crease at the
fixing guide flange.
(1) If there is no tape crease

Turn the tilt screw clockwise so that tape crease
appears once at the flange, and then return the tilt
screw so that the crease disappears.

(2) If there is tape crease

Turn counterclockwise the tilt screw so that the
tape crease disappears.
(Reference) If the tilt screw is turned clockwise
crease appears at the lower flange.

Guide roller

Cassette Tape

Tape

0.3mm

A/C head

• Adjustment
Adjust the height screw

 

visually so that the control head is

visible 0.3mm below the bottom of the tape.

1. Set the cassette tape in the unit.
2. Press the PLAY button to put the unit in the playback

mode.

3. Roughly adjust the height of the A/C head by turning the

height screw until the tape is in the position shown
below.

Mechanism chassis

Cassette tape

Height screw

TiH screw

Azimuth screw

5

00g

Weight to prevent
float (500g)

Notes:
1. Previously set the tracking control in the center position,

and adjust the ATR signal waveform to maximum with X
value adjustment nut. Thereby the tape run rough ad-
justment is facilitated.

2. Especially the outlet side ATR signal waveform must

have higher flatness.

2. Adjustment of A/C head height and azimuth

1

Perform the initial setting of A/C head position by the
method stated in "4-15 Replacement 3".

2

Connect the oscilloscope to the audio output termi-
nal.

3

Using the alignment tape in which 1 kHz linear audio
signal has been recorded, adjust the height screw so
as to get max audio output.

4

Using the alignment tape in which 7 kHz linear audio
signal has been recorded, adjust the azimuth screw
so as to get max audio output.

5

The adjustment of 

3

 and 

4

 twice or three times

repeat, and finally adjust 

4

.

For X value adjustment
Adjust the X value, turning the gear-
type screwdriver.

3. Tape run adjustment

1

Connect the oscilloscope to PB ATR signal output
test point, set oscilloscope sync to EXT, trigger-input
the PB CHROMA signal (head switching pulse).

2

Rough adjustment of X value
Tentatively fix A/C head arm screws 

1

  by the method

described in 4-15 "Replacement 3".
Playback the alignment tape (VROCPSV) and
shortcircuit between TP801 and TP802. As a result
the auto-tracking is automatically cancelled, so that
the X value adjustment mode is set.
Move the A/C head with the X value adjustment gear
driver (JiGDRiVER-6) by the method shown in Fig-
ure 4-33, and adjust the A/C head so as to get the
maximum ATR signal waveform. (Note: When the A/
C head is adjusted, adjust so that the maximum ATR
signal waveform is obtained nearest the position of
initial setting made in 4-15.)