Marshall JCM2000 TSL100 amplifier repair

This poorly TSL100 came to us with some quite worn valves. After replacing all the valves and some quite extensive testing it turned out it was suffering from a common thermal bias drift issue that some of these amps experience.

After replacing the main board (seen here in the picture) it is working well and sounding good with no bias issues. We can usually replace the board (including the board itself) for just over the retail price of a new one.

Here are some of the most common symptoms associated with this issue:

  • Valves repeatedly popping,
  • Valves red plating (glowing bright orange/red)
  • HT fuse popping regularly
  • Amp overheating/burning smells

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