bugera v 22 squeal/ hum

[leadfootbuell]

hello, this is my first post, and I am happy to have discovered this forum. I have encountered a problem in a bugera v22 that seems to be in the transformer that switches the output power to 4,8,16 ohms. I tap it with my finger when its on, and it reacts like a harmonic tube. I have never worked on a tube amp that has a circuitry board like this, and so far im not impressed. hopefully someone has some insight to the bugera brand, and possibly a manual. I did manage to find a schematic, but it basically shows wiring layout, and is totally non descriptive as far as values, voltages, and type of part. I agreed to look into this amp for a friend, since the last person he had looking at it has had it for 6-7 months and didn't even check it out. I work on various electronics, guitars,c.b.s, linears. and residential and commercial electrical systems, so I kinda know a little bit about a few things! I am not a c.e.t., so I would appreciate any help I can get, in laymans terms. thank you

[Jazz P Bass]

Welcome to the site.

Question: tapping 'what' causes harmonic tube noise?

[eschertron]

bugera is a behringer brand, that may help locate a schematic. This page http://music-electronics-forum.com/t41121/ has some links. I didn't look to see if yours was in there.

[leadfootbuell]

tapping the transformer that steps down output voltages, and puts out 4,8, or 16 ohms. it is located after the power tubes, and before the output jacks.

[Jazz P Bass]

Never had that issue: 'tapping on the output transformer makes a noise'.

I think you need to verify that it is not a tube doing that (sympathetic vibration).
If any, it would most probably be a preamp tube.
The output tubes will naturally make a thump when tapped.

Possibly you could remove the output transformer from the chassis to narrow it down.

[olddawg]

I have one of these amps. Love it! The impedance selector switch is located right next to the effects loop jacks. I would start by cleaning the switch and the jacks with Craig Dioxit D5. Keep in mind that any banging around gets physically conducted. General maintenance is a good start while you are in there. Clean all pots, jacks and switches. Also these amps like to shake themselves apart if you use them a lot. Tighten all screws. Take a good look at the screws mounting the baffle and speaker. Half of mine shook out before I noticed. And... there have been weird issues with the footswitch if you have an early production one. As a side note... he might want to see if it is still under factory warranty?

[mozwell]

Found this in my travels

[Enzo]

Or here:
http://bmamps.com/Schematics/Bugera/..._Schematic.pdf

[Steve A.]

There are two versions of the V22, the original and the Infinium (which supposedly will match any pair of EL84 output tubes.) I haven't yet found the schematic for the V22 Infinium (I have the head incarnation.)

Steve Ahola