VHS MECHANICAL ADJUSTMENT MANUAL VII

2. Alignment and Adjustment

2-1 Tape Transport System and Adjustment Locations

The tape transport system has been adjusted precisely in the factory. Alignment is not necessary except for the following :

1) Noise observed on the screen.

2) Tape damage.

3) Parts replacement in the tape transport system.

Lower flange height of tape guide is used as the reference for the transport adjustment.

To maintain the height of the tape guide and prevent damage, do not apply excessive force onto the main base.

GUIDE ROLLER "S"

CYLINDER ASS'Y

GUIDE ROLLER "T"

FULL ERASE HEAD

#3 GUIDE POST

TENSION POST

HEIGHT SCREW

PINCH ROLLER

#9 GUIDE POST

TILT SCREW

X - POSITION

ADJUST SILT

AZIMUTH SCREW

#8 GUIDE POST

CAPSTAN

SUPPLY REEL DISK

TAKE UP REEL DISK

Fig. 2-1 Location of Tape Transport Adjustment

FE HEAD

GUIDE ROLLER "S"

CYLINDER ASS'Y

POST TENSION

PINCH ROLLER

GUIDE ROLLER "T"

#8 GUIDE POST #9 GUIDE POST

#3 GUIDE POST

Fig. 2-2 Tape Travel Diagram

ACE HEAD

CAPSTAN SHAFT

MAIN BASE

– 21 –

2-2 Tape Transport System Adjustment

When parts are replaced, perform the required adjustments by referring to procedures for the tape transport system. If there are any changes to the tape path, first run a T-120 tape and make sure excessive tape wrinkle does not occur at the tape guides.

1) If tape wrinkle is observed at the guide roller S, T, turn the guide roller S, T until wrinkle disappears.

2) If the tape wrinkle is still observed at the tape guide, perform the tilt adjustment of the ACE head.

(See page 5-3 of the Service Manual for Test Point

Locations.)

2-2-1 ACE Head Assembly Adjustment

2-2-1(a) ACE HEAD HEIGHT ADJUSTMENT

1) Run the alignment tape (KRV-52NE (NTSC)/52PL

(PAL)) in the playback mode.

2) Observe surface of the audio head using a dental mirror.

3) Turn screw (C) clockwise or counterclockwise until the gap of lower tape edge and the lower edge of the control head is about 0.25mm.

(Refer to Fig. 2-3 and 2-4)

SCREW (A)

TLIT ADJUST

SCREW (C)

HEIGHT ADJUST

X-POSITION

ADJUSTING SLIT

SCREW (B)

AZIMUTH ADJUST

SCREW (D)

X-POSITION LOCKING

Fig. 2-3 Location of ACE Head Adjustment Screw

AUDIO HEAD

2-2-1(b) ACE HEAD TILT ADJUSTMENT

1) Playback a blank tape and observe the position of the tape at the lower flange of tape guide.

2) Confirm that there is no curl or wrinkle at the lower flange of tape guide as shown in Fig. 2-5 (B).

3) If a curl or wrinkle of the tape occurs, slightly turn the screw (A) tilt adjust on the ACE head ass’y.

4) Reconfirm the ACE head height.

WRINKLE

(BAD)

Fig. 2-5 Tape Guide Check

(GOOD)

2-2-1(c) AUDIO AZIMUTH ADJUSTMENT

1) Load alignment tape (KRV-52NE (NTSC)/52PL

(PAL)) and playback the NTSC : 5KHz (PAL :

4KHz) signal.

2) Connect channel-1 scope probe to audio output test point.

3) Adjust screw (B) to achieve maximum audio level.

(See Fig. 2-3)

2-2-1(d) ACE HEAD POSITION (X-POINT)

ADJUSTMENT

1) See “2. Alignment and Adjustment” for ACE Head position (X-Point) adjustment.

VIDEO HEAD

0 ~ 0 .25 mm

CONTROL HEAD

Fig. 2-4 ACE Head Height Adjustment

– 22 –

2-2-2 Linearity Adjustment

(Guide roller S, T adjustment)

1) Playback the alignment tape (KRV-51N2

(NTSC)/51P (PAL)) (SP mode, Mono Scope).

2) Observe the video envelope signal on an oscilloscope (triggered by the video switching pulse).

3) Make sure the video envelope waveform (at its minimum) meets the specification shown in

Fig. 2-6.

If it does not, adjust as follows : b a c a b c d c,b,d/a 63%

Fig. 2-6 Envelope Waveform Adjustment d

Note :

a=Maximum output of the video RF envelope.

b=Minimum output of the video RF envelope at the entrance side.

c=Minimum output of the video RF envelope at the center point.

d=Maximum output of the video RF envelope at the exit side.

H'D SWITCHING

PULSE

A

ENVELOPE

A

B

B

4) If the section A in Fig. 2-7 does not meet the specification, adjust the guide roller S up or down.

5) If the section B in Fig. 2-7 does not meet the specification, adjust the guide roller T up or down.

Fig. 2-7 Adjustment Points

6) Play back the alignment tape (SP mode, Mono Scope).

7) Connect an oscilloscope CH-1 to the Envelope and CH-2 to the H’D SW Pulse for triggering.

8) Turn the guide roller heads with a flat head ( ) driver to obtain a flat video RF envelope as shown in Fig. 2-8.

IDEAL ENVELOPE

S HEIGHT TOO HIGH

S HEIGHT TOO LOW

T HEIGHT TOO HIGH

T HEIGHT TOO LOW

GUIDE ROLLER S

Fig. 2-8 Guide Roller S, T Height Adjustment

– 23 –

GUIDE ROLLER T

2-2-3 Check Transitional Operation from

RPS to Play

Check transition from RPS mode to play mode :

Using a pre-recorded SP tape, make sure the entry side of envelope comes to an appropriate steady state within 3 seconds (as shown in Fig. 2-9).

If the envelope waveform does not reach specified peak-to peak amplitude within 3 seconds, adjust as follows :

1) Make sure there is no gap between the supply roller lower flange and the tape.

If there is a gap, adjust the supply guide roller again.

2) Change operation mode from the RPS to the play mode (again) and make sure the entry side of envelope rises within 3 second.

ENTRANCE SIDE ENVELOPE

2-2-4 Envelope Check

1) Make recordings on T-120 (E-120) and T-160

(E-180) tape.

Make sure the playback output envelope meets the specification as shown in Fig. 2-10.

2) Play back a self recorded tape (recording made on the unit using with T-120 (E-120).

The video envelope should meet the specification as shown in Fig. 2-10.

In SP mode, (A) should equal (B).

If the head gap is wide, upper cylinder should be checked.

A

B

Fig. 2-9 Video Envelope Rising when Operation mode Changes from RPS to Play Mode

Fig. 2-10 Envelope Output and Output Level

2-2-5 Tape Wrinkle Check

1) Run the T-160 (E-180) tape in the playback, FPS,

RPS and Pause modes and observe tape wrinkle at each guide.

2) If excessive tape wrinkle is observed, perform the following adjustments in Playback mode :

◆ Tape wrinkle at the guide roller S, T section :

Linearity adjustment.

◆ Tape wrinkle at tape guide flange :

ACE head assembly coarse adjustment.

2-3 Reel Torque

1) The rotation of the capstan motor causes the

Holder Clutch Ass’y to rotate through the Belt

Pulley.

2) The spring wrap PLAY/REV of holder clutch ass’y drives the disk reel S, T through gear idle by rotation of gear center ass’y.

3) Brake is operated by slider cam at FF/REW mode.

4) Transportation of accurate driving force is done by gears. (Gear Center Ass’y)

Note : If the spec. does not meet the followings specifications, replace the holder clutch ass’y and then recheck.

MODE

PB

RPS

<Table 2-1>

TORQUE g/cm

42 ± 11

145 ± 30

GAUGE

Cassette Torquemeter

Cassette Torquemeter

– 24 –

MEMO

– 25 –

VHS MECHANICAL ADJUSTMENT MANUAL VII

9-921-790-11

Sony Corporation

Network Entertainment Group

– 26 –

2001A1600-1

© 2001.1

Published by Quality Assurance Dept.