• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Velleman K8010 monoblock tube amplifiers


We've not had this problem. And I know this is old, but it sounds like something isn't upto spec 100%. Or a mistake was made in their assembly. I would double check everything (be safe about electricity).

Heres a review we did on this Amp. We did it for fun, not many people look at this stuff. And there was no reviews on line. Let me know how this turned out and if you got it fixed.

Velleman Class A K8010 Tube Monoblock Amplifiers - Review! - YouTube
Is the plate on the valve on the left glowing red. If so the bias is set too hot. I can see from the schematic that if the bias pot wiper goes O/C then 0V is put of the grid and the valve will pop. I think if I had this amp I would convert it to servo bias.
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Could be although modern caps are used. The grid leak resistors of 220k + pot + 100k exceed the value on the KT88 datasheet so there could also be thermal runaway. I would be using 100k but this requires changes to the driver stage. This I found on the WEB so cannot vouch to stability etc. The screen resistors have been changed too. It does seem to indicate a problem in this area. Check also that the bias pots are properly soldered.

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