SHARP 21BFX1
Service Manual

21B-FX1

PIF PURITY ADJUSTMENT

No. point Adjusting procedure/conditions Waveform and others

Tuner IFT Get tuner ready to receive CH. E 9 1 PURITY ADJ. 1. Receive GREEN-ONLY signal. Adjust the

( PRESET ) signal,but with no signal input. beam current to ~700 µA.
10k 1n60 1000p

Adjust PLL data. 2. Degauss CRT enough with the degausing coil. a 2. Connect the sweep generator's output cable to the tuner antenna. ( RF SWEEP )

b Note: Follow the Job Instruction Sheet to ad-

just the magnetic field.
Oscilloscope IF OUT

Vertical Bv: +0.030 mT (0.30 gauss) 3. Adjust the sweep generator's to 80dBµV.

4. Connect the response lead ( use LOW IMPED100k 1000p 75ohm Horizontal Bh: +0.020 mT (0.20 gauss)
field and keep static convergence roughly must have the probe alone connected ).
E-9 CH adjusted. 5. Set the RF AGC to 0 6 V no saturation with

ANCE probe with wave detector ; see Fig.1 ) to (Reference: page 10/23) tuner's IF output terminal. ( This terminal Fig.1 3. Maintain purity magnet at the zero magnetic Fig. 4-1
4. Observe points a, b as shown in Fig. 4-1 the waveform. 5. Orient the raster rotation to 0 eastward.

50mm

6. tuner IF coil obtain waveform as P C through microscope. Adjust landing to the
-1.5+/-0.8dB

shown in Fig. 2. A rank requirements. A Fig.2 6. Tighten up deflection coil screws. Note: Be sure to keep the tuner cover in posi7. Make sure CRT corners landing meet the A rank requirements. If not, stick the magnet sheet » Tightening torque: 108 20 N (11 ± 2 kgf) tion during this adjustment. B

A = B RF-AGC 1. Receive "PAL COLOUR BAR" signal. Note: For the 50 ohm signal 2

to correct it. TAKE OVER » Signal Strength: 54 ± 1 dBµV (75 ohm open) strength gauge, when not Note: This adjustment must be done after POINT ADusing 50/75 impedance warming up the unit for 30 minutes or Fig. 4-2 JUSTMENT 2. Connect the oscilloscope to TP201 (Tuner�s AGC adapter, signal strength is longer with a beam current over 700 µA. (I2C BUS Terminal) as shown in Fig. 3. 52±1dBµV(75 ohm open), inNote: Set the service mode by TP1001 & (on right of the CRT) CONTROL) stead of 54±1dBµV (75 ohm TP1002 (short) then press factory proc-

Rank "A"

Oscilloscope + TP201 Precaution: The loss of using mono colour mode.

8
ONLY

open). ess R/C key change to RGB 0.1V impedance adapter. * For the following colours press R/C RGB key to �
change. A

Bias box TV Set

+ GREEN BLUE RED

B

� Signal-colour » Bias box: About 4.5 V screen cleared A = B

Fig. 3
Fig. 4-3 3. Call "AGC" mode in service mode. Adjust the

"AGC" bus data to obtain the Tuner output pin Rank "A" drop 0.1V below maximum voltage. (on left of the CRT)

4. Change the antenna input signal to 63~67dBµV,

and make sure there is no noise. * Press R/C RGB key for 1 sec-

5. Turn up input signal 90~95 dBµV to be sure ond in NORMAL MODE, the
mono colour mode. Text R.G.Cy � Key can be directly use change to other colours screen.

that there is no cross modulation beat. colour will change to RGB

8-1 8-2