I have a 40watt JCM2000 combo, and it's a great little amp for everything I've ever needed it for, but lately when you have the volume turned up to 7+, it instantly blows a fuse. Obviously this is a problem, because with a 40watt amp you really need to push it when jamming (which is great usually, as it gives the valves a good push... but not when it is blowing fuses because of it!).

Any ideas as to what it could be?

Also, the overdrive volume knob has been giving me a bit of trouble lately, works fine between 1 and 3, works fine between 7 and 10, but anywhere in the middle and the sound almost drops out completely. I'm thinking this is probably just a loose wire behind the knob, and something I could fix myself ?

Cheers!

Well the knob issue is probably just a dirty pot. Some electrical spray contact cleaner might sort it out. Servisol comes to mind. As for the other problem, I don't know. If you run a curcuit breaker on the plug end, check its working properly, if not then maybe invest in one. It won't necessarily solve the problem but I always advise using one on large electrical equipment to stop voltage surges etc.

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Power tubes going bad can cause this as well. When was the last time you changed the tubes?

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these days marshall uses chinese pots which are SHIT. I feel your pain man, i have a marshall too get it replaced. a new pot costs about 3-5$, and i have no idea how much installation will cost.

About the fuse, sounds like your powertubes are either going bad, or arent matched (which can be a result of them going bad, and can also make them go bad faster). To fix: new tubes, re-bias, new fuse.

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