(Topic ID: 224860)

Gottlieb Buck Rogers Driver Board keeps blowing CEN-U45 Q29

By cshelden

5 years ago



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  • Latest reply 5 years ago by cshelden
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#2 5 years ago

Grounding the case only tests the wiring between coil and driver board & doesn't test Q45.
Make sure wiring between Q45 emitter and ground is OK. Original connectors/contacts?

Are you sure the U45's are bad? Could be the corresponding 2N3055 at Q45 - might have lower than normal gain.
Where did you get the 2N3055's? Not Toshiba's by chance?

Not likely but also check resistor R39 for proper value and not shorted.

#4 5 years ago

Unlikely for these new On-Semi 2N3055G transistors to be bad. There is a large, bad batch of Toshiba 2N3055's floating around out there - horribly low gain. I bought ~500 of them... unfortunately, nearly all of them are in the Omaha land fill.

Did you check resistor R39 value? He should be about 9.1 ohms.
Hopefully this one isn't 900 ohms. If so - there's your problem.

If R38 is too low - that can be a problem as well. S/B 1K within ~5%.

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