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DE- Blowing lamp driver transistor

John Price

Member
May 31, 2020
75
21
8
Tottenham ON
Having a problem with my ST. It keeps blowing Q66 transistor for lamp column 6 after a couple of days. Have checked for blown diodes or shorted lamp sockets on that column, all is good. Is it a board problem or could it be something else?
 

sylvain

Active Member
Apr 27, 2013
209
75
28
Ottawa, ON
Could be a few things:
- intermittent short in a bulb on that line, or something close to a socket intermittently shorts to something
- ensure your replacement transistor is proper (correct specs/number)
- check resistor R33 for proper value
- check pre-driver transistor Q59.

Good luck!
-Sylvain.