I have finished my Pass preamp, but was so stupid to forget ground connection from PSU to line stage before plugging in to my power amp. Drains on my FETS measured 118 volt, where they should have been 30 v.
See this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=5367
Problem fixed, unfortunately my new pre was plugged into my power amp, Audio 60 (Doxa) from mid 80s, while I was testing.
My stupidity has blown away my Audio 60. When I turn it on, either using my my old pre-amp or my variable cd-direct, it get this VERY HIGH houling sound. Guess my power amp was getting 118 volt or so from the pre. My speakers are OK.
A friend of mine believes that my NEC transistors at the output are not damaged, only the small signal transistors in the input.
See photo:
[IMGDEAD]http://2bak.homepage.dk/audio60_5.jpg[/IMGDEAD]
Red arrows are two BC 557B and two B547C.
Yellow arrows are two BD 529 and two BD 530.
The black heat marks over the resitors are NOT from this mistake, since I saw it long time ago !
I have the following questions:
1. Is it likely that my NEC power transitors also are damaged. Would it be able to make make this howling sound then?
2. BC 557B and B547C are easy to find today. Are there any better ones I could use instead? Better quality, I mean. I can't find BD 529 and BD 530 anywhere on the Internet. Which other good types could replace them?
3. Would 118 volt at input normally burn off all eight input transistors, or could I hope for that only BC 557B and B547C are burned?
4. How do I measure using a multimeter if a transistor is intact?
Thanks
/Jan
See this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=5367
Problem fixed, unfortunately my new pre was plugged into my power amp, Audio 60 (Doxa) from mid 80s, while I was testing.
My stupidity has blown away my Audio 60. When I turn it on, either using my my old pre-amp or my variable cd-direct, it get this VERY HIGH houling sound. Guess my power amp was getting 118 volt or so from the pre. My speakers are OK.
A friend of mine believes that my NEC transistors at the output are not damaged, only the small signal transistors in the input.
See photo:
[IMGDEAD]http://2bak.homepage.dk/audio60_5.jpg[/IMGDEAD]
Red arrows are two BC 557B and two B547C.
Yellow arrows are two BD 529 and two BD 530.
The black heat marks over the resitors are NOT from this mistake, since I saw it long time ago !
I have the following questions:
1. Is it likely that my NEC power transitors also are damaged. Would it be able to make make this howling sound then?
2. BC 557B and B547C are easy to find today. Are there any better ones I could use instead? Better quality, I mean. I can't find BD 529 and BD 530 anywhere on the Internet. Which other good types could replace them?
3. Would 118 volt at input normally burn off all eight input transistors, or could I hope for that only BC 557B and B547C are burned?
4. How do I measure using a multimeter if a transistor is intact?
Thanks
/Jan