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Alesis Spitfire SS Amp output finals failed

plutonium233

Nov 1, 2006
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Nov 1, 2006
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A friend gave me an Alesis Spitfire guitar amp that died on him. The output finals went in it and blew the power supply fuse. I bought two new transistors tip31c and tip32c (npn/pnp) and replaced them. I can turn the amp on now and it does not blow the fuse, however, there is no sound. I am beginning to wonder if the output transistors took out a driver or something too. The people at Alesis were kind enough to give me a service document that has schematics and a parts list, so I am attaching the schem. of the main amp board. Based on this schem, which transistors do you think could have gone with the outputs? If I had to guess I would say the c2235 and A965, but I don't know, I havn't taken the advanced circuits courses yet... Oh, when you turn it way up you can faintly hear it play.

Thanks,
Kyle
 

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plutonium233

Nov 1, 2006
6
Joined
Nov 1, 2006
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I was just thinking, Is is possible that the failure could have taken passive components as well? (like the big power resistors)
 

plutonium233

Nov 1, 2006
6
Joined
Nov 1, 2006
Messages
6
Does anyone know a good way to detect the presence of an audio signal without a scope. I would think there would be a way to use headphones to do this, but I want to see what you guys think first.
 

plutonium233

Nov 1, 2006
6
Joined
Nov 1, 2006
Messages
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I noticed that there is a protection circuit on here as well. I was wondering if that could have been taken out since parts of it are mounted on the heat sink and could have been overheated or damaged. I plan on ordering all of the transistors back the the beginning of the amp stage and changing them all. Should I change any other parts as well?
 
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