Philips Fa 951 (2sd1895 and 2sb1255)

[crissmuty]

Hallo, I'm "burning out" half of the final transistors. Can someone
tell me what am I doing wrong? Should I verify something? I checked
already all the components on the board and everything looks OK, but
after 5-6 minutes the transistors show a B-E short, and nothing works
anymore.Thank's for your time. Best regards. Criss

 

[Asimov]

"crissmuty" bravely wrote to "All" (22 Nov 03 08:47:55)
--- on the heady topic of "Philips Fa 951 (2sd1895 and 2sb1255)"

cr> From: crissmuty@web.de (crissmuty)

cr> Hallo, I'm "burning out" half of the final transistors. Can someone
cr> tell me what am I doing wrong? Should I verify something? I checked
cr> already all the components on the board and everything looks OK, but
cr> after 5-6 minutes the transistors show a B-E short, and nothing works
cr> anymore.Thank's for your time. Best regards. Criss

This is an audio amplifier right? Put 100 ohm power resistors (or a
lamp) in series with the collectors to limit the current until you can
determine which voltages are wrong. It may be an idle current or a DC
balance problem. Don't connect speakers until you are sure it is fixed.

.... Is reactance then illusory? No, it just appears that way...

 

[crissmuty]

Thank you for your answer.
Yes it is a Amplifier. I think also there is a dc current balance
problem. The only problem is that the transistors are very expensive
and I don't want to try again without a good advice.