Hello all: Having an issue with one of the mono block that I built from P. Millets schematic and was wondering if anyone can shed some light on the issue. So I built the P.Millet 50w mono block engineers amp using his board and followed the schematic exactly as prescribed and the amp worked great. I had it in storage for 4-5 months and recently hooked it up, checked the bias (running it between (350-425mV) and everything seemed in spec. Then I started hearing intermintent static on one channel and notice bias voltage jumping past the 500mV and beyond. I check all the tubes and they were good. So my question is what could be causing the spike in bias voltage with the static to the speakers? I looked at schmatic and was thinking it could be the IXCP10M45 current regulator? This seems to occur around after 30 minutes of playing, I have also traded out all tubes and problem still persists. Thanks for any assistance in this matter
Maybe some dust/corrosion on the bias setting trim/pot from storage.
Shut it down, note the position of the bias set trim/pot, then move the trim/pot several times fully left and right, and/or treat it with some deoxid if you happen to have it.
Try again and see if that fixes it.
Jan
Shut it down, note the position of the bias set trim/pot, then move the trim/pot several times fully left and right, and/or treat it with some deoxid if you happen to have it.
Try again and see if that fixes it.
Jan
I should have stated that it just wasn't used. It was just sitting in my cabinet not being used.
Trim pot is fine, Bias of both 6HJ5's are close range of each other (+- .020mV). As I mentioned it starts acting up intermittently after running for 15-20 minutes then I would get loud static from speaker and bias voltage spikes. I would have to turn it off.