VC-MH742HM (serv.man20). Electrical adjustments - Sharp VCR Service Manual (repair manual). Page 2

Measuring
instrument

Mode

Cassette

Dual-trace oscilloscope
Colour TV monitor

Playback

Alignment tape (VROCPSV)

Test point

Pin(2) of P201 (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.

(VROCPSV)

2. Press the PLAY button.

(Playback picture on the monitor screen.)

3. Make for a moment short-circuit P802, located at the

front side on the main PWB.
Be sure that all the fluorescent display tubes light up
into the TEST mode.(See Note below)
Be sure the "PLAY" appears in the fluorescent display
tubes flashing (about 1Hz) into the auto PG adjust-
ment operating.

When the manual PG adjustment, obseve the wave-
form with an oscilloscope and make adjustment FF or
REW button so that the specification.

4. Stop the "PLAY" appears in the flashing of fluorescent

display tubes at adjusted.

5. Press the STOP button in the return to normal mode.
6. Make this checking of waveform on the oscilloscope

screen be as shown in Figure 5-2. just after the head
switching point have been adjusted.

1

Set-up of TEST mode.
When the adjustment of HEAD SWITCHING POINT,
AUTO TRACKING function is invalid.

2

When the cassette housing control ass’y is removed,
set-up of mechanism operating mode.

1) Replug the AC power cord it a few minutes later.
2) Make a short-circuit P801 located at the front side on

the main PWB, and press both tracking control button
at the same time to set the tracking in center.

3) AC power cord is plugged in.
4) You can mechanism operatig mode, Replug the AC

power cord a few minutes later.

Measuring
instrument

Mode

Cassette

Colour TV monitor

Playback

Self-recorded tape
(SP/LP mode)(See Note below)

Control

Tracking control buttons (+) or (–)

Specification

Minimized noise on
monitor screen

1. Have the unit to receive a good TV broadcast or feed

a video signal to the VIDEO IN jack. (See note 

2

below)

2. Set the tape speed in SP mode by using the remote

control and record the signal on tape.

3. Rewind and play the tape where signal was recorded

in above step.

4. Press the SLOW button on the remote control, and

playback the recorded portion in the slow mode.

5. Make for a moment short-ciucuit  P802, located at the

front side on the main PWB.
Be sure that all the fluorescent display tubes light up
into the TEST mode.

6. Look at the monitor screen and adjust the (+) or (–)

TRACKING buttons so that the there is noise disap-
pears from the screen.

7. Press the STOP button to return to normal mode.
8. Play the tape a few seconds then press the SLOW

button again and make sure there is on noise in the
screen.(For the LP mode put adjustment at the same
adjustmet way as SP mode.)

1

Self-recorded tape means a cassette whose pro-
gram was recorded by the unit being adjusted.

2

The TV program will not be recorded if RCA or 21pin
plugs are pluged in to the AUDIO/VIDEO input
terminals.

6.5

±

0.5H (lines)

CH-1: 1V/div 50

µ

s/div

CH-2: 2V/div 50

µ

s/div

V-sync.

CH-1
HEAD
SWITCHING
PULSE

CH-2
VIDEO OUT