Question about Marshall JVM410C 100 Watts Valve Guitar Combo

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My brand new Marshall JVM410C 100 watt combo gets very hot. Is this normal?

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"Very" is relative... yes they do get warm but nothing you should not be able to hold your hand for extended period.

The amps are probably only 30% efficient overall, and the rest comes out as heat... it has to go somewhere, so the case must get hotter than the surrounding air to get rid of the energy.

Posted on Sep 13, 2010


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Possible that the output tubes that were replaced are drawing too much current, hence the popping sound (may be "motorboating", one common word to describe a similar sound)

This means the tubes need to be biased properly. You need to get it to someone who knows what they are doing, ie a good amp tech, not GC. The voltages here are dangerous.

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Just because the voves are lit doesn't mean there is the high voltage power to the valves.

ALSO the smaller valves have TWO heaters in them and if one half has burned out that would cause the symptom. Check if the smaller 12AX7/12AT7 types all have two heaters burning. Verify that the standby switch has not gotten bumped off.

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Given the symptoms you have, the following possibilities are likely:

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