Bugera V22 hum

[fossilshark]

Hi, I have a Bugera V22 on the bench here and there was no audio when I first got it. After making sure all the voltages were correct I resoldered all the dogshit factory solder joints and that brought it back to life.

There is still a bad hum that is not affected by any controls other than master volume, and the hum gets really bad when its in pentode mode.

I am thinking it needs new power tubes, does this sound correct?

[sluckey]

If power tubes are causing hum the master volume would not affect the hum.

[mk_716]

heads up fossilshark,
    I came by two of these, both with serious problems.   Check the wiring to the Triode/Pentode switch  - one of them I had a short/melted insulation in the wire bundle coming to the switch from the pcb.

I've gutted out the chassis (both) and am building other projects into them.   The transformers were good, nice cabinet, 12" speakers..

m.

[fossilshark]

Thank you very much

[fossilshark]

 

So I checked the switch and wires and they seem fine.

The hum is only present when the master volume is turned up enough for signal to get through, but the hum does not get any louder or quieter with the master volume. Once its present no knob affects the hum.

Could it be the filter caps?

[AmberB]

Well, filter caps are a possibility at least...

[fossilshark]

How would I check? Should I break out the O'scope and see if the hum is on b+?