Samsung CF21M Service Manual page 56

5-1-13 V Size or Pos. Variation Failure
IC250 Pin 23 output varies with
different DAC values?
Yes
Check and replace IC250 and IC301.
5-1-14 High Voltage Failure
Q504 gate driving pulse exist?
12
The waveform is right?
Yes
Are there some voltages
(350V, 30V, -210V, etc)
at secondary part of FBT?
Yes
Done.
CF21M*
No
Check some parts around IC250.
Check bias voltage.
Check +12 V line.
No
Check and replace
Q502, Q503, R511, IC501.
No
Check and replace Q504, D508,
D509, D530, D507, D505.
5 Troubleshooting
WAVEFORMS
Q504, Gate
12
5-7