Troubleshooting - Nokia 920C Service Manual

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.
Repeating start?
No
IC601 Pin 1 waveform is right?
1
Yes
IC602 and IC604
are right?
Yes
Normal operation
Yes
Verify voltages.
Yes
Done.
720C/920C
Yes
Check and replace D601, D604, D663,
Q632, and Q664.
No
Check and replace IC601,
IC602, IC604.
No
Replace parts and verify voltages.
No
Replace Main board.
WAVEFORMS
544 V (IC601, #1)
1
CH1 P-P = 544 V CH1 RMS = 332.4 V
5-1