720C/920C
5-1
5 Troubleshooting
5-1 Parts Level Troubleshooting
Notes:
1. If a picture does not appear, fully rotate the brightness and contrast controls clockwise and reinspect.
2. Check the following circuits.
• No raster appears: Power circuit, Horizontal output circuit, H/V control circuit, and H/V output circuit.
• High voltage develops but no raster appears: Video output circuits.
• High voltage does not develop: Horizontal output circuits.
5-1-1 No Power Supply
Check and replace FG601, D601,
IC661, IC662.
Done.
Repeating start?
Check and replace D601, D604, D663,
Q632, and Q664.
No
Yes
IC601 Pin 1 waveform is right?
Check and replace IC601,
IC602, IC604.
Yes
No
IC602 and IC604
are right?
Replace parts and verify voltages.
Yes
No
Normal operation
Replace Main board.
Yes
Yes
No
WAVEFORMS
1
1
544 V (IC601, #1)
CH1 P-P = 544 V
CH1 RMS = 332.4 V
Verify voltages.
Summary of Contents for 720C
Page 33: ...720C 920C 6 1 6 1 720C Exploded View and Parts List ...
Page 34: ...720C 920C 6 2 6 2 920C Exploded View and Parts Lists ...
Page 80: ...R299 720C 920C 10 2 10 2 MICOM Parts Schematic Diagram ...
Page 81: ...720C 920C 10 3 10 3 Horizontal Vertical Processor Parts Schematic Diagram R265 C272 R262 ...
Page 83: ...R561 R562 R501 C530 L521 R523 R526 720C 920C 10 5 10 5 High Voltage Parts Schematic Diagram ...
Page 84: ...720C 10 6 1 10 6 1 720C Video Parts Schematic Diagram ...