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Doh!!!!
Silly reason. The screws making connection to TR9 weren't done up and so TR9 was out of circuit. All the base current coming out of TR7 could only go through R16 and it would have been maximized as there was no TR9 to turn on and give the correct feedback. Hence R16 popped and acted as a fuse for the rest of the output stage.
New R16 and the screws tightened ad it was fine. Used it at a gig on Saturday - All OK. Owner (the banjo player - err yes I did say banjo) was very happy. (Good gig as well.)
My fault in the first place I had to replace a faulty jack socket at the send/return socket seldom get used and the contacts oxidized. So replaced with gold plated ones which were only slightly more expensive.
I agree with all your comments - good reliability advice. I’ve already done all those things on a previous visit to the amp. In the UK here parts are easy form companies like Farnell or RS, both of which I think are global.
Once again, many thanks for your help. I had started to trace the circuit myself but you saved me a load of time. The half I had done did agree with yours exactly.
Jon
Silly reason. The screws making connection to TR9 weren't done up and so TR9 was out of circuit. All the base current coming out of TR7 could only go through R16 and it would have been maximized as there was no TR9 to turn on and give the correct feedback. Hence R16 popped and acted as a fuse for the rest of the output stage.
New R16 and the screws tightened ad it was fine. Used it at a gig on Saturday - All OK. Owner (the banjo player - err yes I did say banjo) was very happy. (Good gig as well.)
My fault in the first place I had to replace a faulty jack socket at the send/return socket seldom get used and the contacts oxidized. So replaced with gold plated ones which were only slightly more expensive.
I agree with all your comments - good reliability advice. I’ve already done all those things on a previous visit to the amp. In the UK here parts are easy form companies like Farnell or RS, both of which I think are global.
Once again, many thanks for your help. I had started to trace the circuit myself but you saved me a load of time. The half I had done did agree with yours exactly.
Jon
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