Sharp 20A1-RU, Service Manual

7

20A1-RU
21A1-RU
21A2-RU

7-2

7-1

PURITY

 ADJUSTMENT

No.

Adjusting point

Adjusting procedure/conditions

W

aveform and others

PURITY

 ADJ.

1

.

Receive the GREEN-ONL

Y

 signal. 

Adjust the

beam current to about 500 

µ

A.

2

.

Degauss the CR

T

 enough with the degausing coil.

Note:

Follow the Job Instruction Sheet to ad-

just the magnetic field.

V

ertical Bv

:

+0.040 mT (0.40 gauss)

Horizontal Bh

:

+0.020 mT (0.20 gauss)

(See page 6.)

3.

Maintain the purity magnet at the zero magnetic

field and keep the static convergence roughly

adjusted.

4

.

Observe the points a, b as shown in Fig. 4-1

through the microscope. 

Adjust the landing to the

rank A

 requirements.

5.

Orient the raster rotation to 0 eastward.

6.

T

ighten up the deflection coil screws.

»

 T

ightening torque: 108 

±

 20 N (1

1 

±

 2 kgf)

7.

Make sure the CR

T

 corners landing meet the 

A

rank requirements. If not, stick the magnet sheet

to correct it.

Note:

T

h

is

 a

d

justment must be done after

warming up the unit for 30 minutes or

longer with a beam current over 500 

µ

A.

Note:

Set the service mode by TP1001 &

TP1002 (short) then press factory proc-

ess R/C RGB key to change to RGB

mono colour mode.

*

For the following colours press R/C RGB key to

change.

1

*

Press R/C RGB key for 1 sec-

ond in NORMAL MODE, the

colour will change to RGB mono

colour mode.

The 

TEXT

 Key "R. G. Cy" Key

can be directly use to change

to other colours screen.

a

b

A

B

A

B

A = B

A = B

Rank "A" 

(on the right of the CRT)

Rank "A"

(on the left of the CRT)

Fig. 4-1

Fig. 4-2

Fig. 4-3

Green-only

Blue-only

Red-only

Signal-colour

screen cleared

PIF ADJUSTMENT

No.

Adjusting point

Adjusting procedure/conditions

W

aveform and others

T

uner IFT

( PRESET )

1

1

.

Get the tuner ready to receive the CH. E - 9

signal,but with no signal input.

Adjust the PLL data.

2.

Connect the sweep generator's output cable to

the tuner antenna. ( RF SWEEP )

3.

Adjust the sweep generator's to 80dBuV

.

4.

Connect the response lead  ( use LOW IMPED-

ANCE probe with wave detector ; see Fig.1 ) to

the tuner's   IF output terminal. ( 

This terminal

must have the probe alone connected ).

5.

Set the RF 

AGC to 0 - 6 V with no saturation with

the waveform.

6.

Adjust the tuner IF coil to obtain the waveform as

shown in Fig. 2.

Note:

Be sure to keep the tuner cover in position

during this adjustment.

RF-AGC

T

AKE OVER

POINT AD-

JUSTMENT

(I

2

C BUS

CONTROL)

1.

Receive "P

AL

 COLOUR BAR" signal.

»

Signal Strength: 57 

±

 1 dB

µ

V (75 ohm open)

2.

Connect the oscilloscope to 

TP201 (T

uner

’s

 AGC

T

erminal) as shown in Fig. 3.

3.

Call "AG" mode in service mode. 

Adjust the "AG"

bus data to obtain the 

T

uner output pin drop 0.1V

below maximum voltage.

4.

Change the antenna input signal to 63~67dB

µ

V,

and make sure there is no noise.

5.

T

urn up the input signal to 90~95 dB

µ

V to be sure

that there is no cross modulation beat.

Note: For the 50 ohm signal

strength gauge, when not

using 50/75 impedance

adapter

, signal strength is

52

±

1dB

µ

V(75 ohm open), in-

stead of 57

±

1dB

µ

V (75 ohm

open).

Precaution: The loss of using

impedance adapter

2

»

 Bias box: 

About 4.5 V

Oscilloscope

0.1V

TV Set

Bias box

TP201

+

+

–

–

Fig. 3

E-9 CH

P

                C

10k

100k

1n60

75ohm

IF OUT

-1.5+/-0.8dB

1000p

Oscilloscope

Fig.1

Fig.2