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Squealing Marshall

4/30/1997 12:52 AM
Squealing Marshall
I have a 1971 Marshall JMP 50 watt head, and when I jumper the channels together it squeals badly and even caused a power tube to blow. Does anybody have any idea what would cause this and how to fix it?
4/30/1997 4:01 PM
R.G. Keen

1. Bad preamp tube  
2. Bad bypass capacitor for preamp section(s)  
3. Faulty grounding of one or another of the  
input jacks or tubes.  
4. Problem with the wire routing inside the  
5. Someone has previously "improved" the insides  
some way.
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