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03-20-2020, 10:44 AM
Hi Noel
Do you know if the board was damaged before or after the other tech did his mod? In any case, that whole section has to be cut out as burned fibre glass is always conductive. Don't use open trimpots.
Although it seems like more work, it may be most cost effective and quicker to remove the whole board and throw it and everything on it away. Install chassis-mounted sockets and use eyelet boards for a new circuit - not necessarily a copy of the old. That was my solution for a similar Mesa experience. This lets you fix everything wrong with the original - lack of grid-stops; folded signal path; poor quality parts; poor design choices; crazy switching circuit; difficult servicing; lack of proper bias pots and measuring.
In the rebuild, use a standard splitter without the negative rail.
Depending on the supply voltage, you might have to get 500V caps and then you can use singles rather than series-connected ones. Modern snap-mount and radial caps are tiny and inexpensive even if they are 10k-hour types. The old caps are past their useful life regardless of how they might measure.
Of course, it might be even more cost effective to scrap the amp. People make bad choices and in the greater scheme of things whatever the customer paid for this is peanuts in the spending life of most musicians who constantly change gear. (To me mesa is always a bad choice).
Have fun
Do you know if the board was damaged before or after the other tech did his mod? In any case, that whole section has to be cut out as burned fibre glass is always conductive. Don't use open trimpots.
Although it seems like more work, it may be most cost effective and quicker to remove the whole board and throw it and everything on it away. Install chassis-mounted sockets and use eyelet boards for a new circuit - not necessarily a copy of the old. That was my solution for a similar Mesa experience. This lets you fix everything wrong with the original - lack of grid-stops; folded signal path; poor quality parts; poor design choices; crazy switching circuit; difficult servicing; lack of proper bias pots and measuring.
In the rebuild, use a standard splitter without the negative rail.
Depending on the supply voltage, you might have to get 500V caps and then you can use singles rather than series-connected ones. Modern snap-mount and radial caps are tiny and inexpensive even if they are 10k-hour types. The old caps are past their useful life regardless of how they might measure.
Of course, it might be even more cost effective to scrap the amp. People make bad choices and in the greater scheme of things whatever the customer paid for this is peanuts in the spending life of most musicians who constantly change gear. (To me mesa is always a bad choice).
Have fun
