Sharp 20CT-250 Service Manual page 9

PAL CHROMA ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions
1 Sub-colour 1. Receive the PAL Colour Bar signal.
adjustment: 2. Set to the P-NORM mode.
I 2 C bus 3. Connect the oscilloscope to TP852 (RED cath-
adjustment ode). (Use a 10 : 1 probe.)
» Range
: 2 V/div.
» Sweep time : 20 µsec/div.
4. Using the remote controller, call the sub-colour
adjustment mode. Adjust the sub-colour data so
that the 75% white and red portions of the PAL
colour bar be at the same level. See Fig. 7 .
5. Clear the adjustment mode.
NTSC CHROMA ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions
1 Sub-tint 1. Receive the NTSC 3.58 Colour Bar signal in the
adjustment: A/V mode.
2
I C bus 2. Connect the oscilloscope to pin (36) of IC801(B-
adjustment Y) .
» Range
: 20 mV/div.
» Sweep time : 20 µsec/div. (Use a 10 : 1 probe.)
3. Adjust the sub-tint data to obtain the waveform
as shown in Fig. 8 .
4. Clear the adjustment mode.
Waveform and others
B
Cy G
W Y 100%W Mg R
Fig. 7
Waveform and others
(B–Y)
A
B
C
W Y Cy G Mg R B
Fig. 8
A=B=C
9-1
PROTECTOR PERFORMANCE CHECK
No. Adjusting point Adjusting procedure/conditions
1 Beam protector 1. Receive the Monoscope Pattern signal.
2. Set the contrast control to maximum.
3. Set the brightness control to maximum.
4. Make a short-circuit between the collector and
emitter of Q851, Q852 or Q853 and make sure
that the protector is activated and the stand-by
mode is called.
2 High-voltage 1. Receive the Monoscope Pattern signal.
protector 2. Connect the bias box to the cathode (R635 side)
of D607.
3. Adjust the bias box voltage to 18 V and make sure
that the protector is not activated.
4. Adjust the bias box voltage to 27 V and make sure
that the protector is not activated.
3 Other protec- 1. In checking the performance of other protectors
tors — for example, the one against shorting of
smoothing electrolytic capacitor of +B line —, pay
attention not to damage or deteriorate any related
element.
A/V INPUT AND OUTPUT CHECK
No. Adjusting point Adjusting procedure/conditions
1 Video and 1. Receive the Colour Bar (100% white colour bar,
audio output 400 Hz, 100% modulation audio) signal.
check 2. Terminate the video output with a 75 ohm imped-
ance. Make sure the output is as specified
(1.0 Vp-p ±3 dB).
3. Terminate the audio output with a 10k ohm im-
pedance. Make sure the output is as specified
(1.76 Vp-p ±3 dB).
2 Video and 1. Using the TV/AV key on the remote controller,
audio input make sure that the modes change in the order of
check TV, AV and TV again and that the video and au-
dio outputs are according to the input and output
terminals for each mode.
Waveform and others
Waveform and others
9-2