Warwick Sweet25.1 Power Stage repair - diyAudio
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Old 21st March 2012, 07:12 PM   #1
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Default Warwick Sweet25.1 Power Stage repair

Hi.
I have Warwick Sweet25.1 combo with burned output stage. Exactly transistors Q27 and Q30 (the schematic is attached). I replaced them, turned the amp on via the electric bulb (itís a good method to start the amp for the first time after power section repair). I measured idle current through R113-R116 resistor and set it around 70mA. I put some music from CD player to input. Everything was ok. Then I connected power supply cord directly (without the electric bulb). After that the amp was working for about 5 minutes, than there was not very loud click in a speaker and again Q27 and Q30 were dead. And F1 fuse was burned too. When I soldered Q27 and Q30 out the amp was still working ok but without them.
I tried this twice
Does anyone have any suggestions how to fix this?

http://www.warwick.de/media/manuals/...SWEET_25.1.pdf
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Old 21st March 2012, 11:09 PM   #2
jaycee is offline jaycee  United Kingdom
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Are you sure the replacement devices were genuine?
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Old 22nd March 2012, 11:00 AM   #3
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Quote:
Originally Posted by jaycee View Post
Are you sure the replacement devices were genuine?
Iím not sure that they are genuine. The marking on the top of the package was correspondent. I also checked voltage drops across BE, BC, CE Ė they were fine. (Before the installation) How can I check new one transistors that they are genuine?
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Old 22nd March 2012, 09:55 PM   #4
jaycee is offline jaycee  United Kingdom
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cut the top off the blown ones and take a look to be sure
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