Bugera 333xl help

[MaxGrove]

I bought a used Bugera 333xl and have LOVED how it sounded but recently it has had 2 problems I need to fix.

1 - the footswitch lights up and the light above each channel on the footswitch changes when you manually change the channel on the amp but pressing the buttons on the footswitch does absolutely nothing.

2 - I replaced the power tubes (and everything worked right) 3 months ago, and after our last gig when we set our gear back up in the practice room, i turned the amp on to warm it up and everything seemed to work correctly. When i plugged in, the clean channel sounded fine, but both the crunch and lead channels put out a mind numbing squeal when i rolled on the guitar volume. Strangely, it does not squeal without a cable in the imput jack. I switched around my gear and ruled out my guitar and the 1/4" cables, and even switched out the preamp tubes to rule them out as well. No change. Please Help!

-Dave from Silhouette

[Structo]

I would suspect that a relay has failed inside the amp for the channel switcher.
Hopefully it is socketed so you can just plug a new one in.

The first suspects in a tube amp should always be the tubes, not matter if it is a new amp or new tubes, they fail.

A bit of a caution before you open up the amp. I haven't seen a schematic for your amp but in general, tube amps use voltages many times in excess of 400 vDC and the power supply filtering caps can store that voltage even if the amp is off and unplugged.
So either learn how to safely discharge those caps or take it to a reputable tech to have it serviced.

[rockon1]

Originally Posted by Structo

I would suspect that a relay has failed inside the amp for the channel switcher.
Hopefully it is socketed so you can just plug a new one in.

The first suspects in a tube amp should always be the tubes, not matter if it is a new amp or new tubes, they fail.

A bit of a caution before you open up the amp. I haven't seen a schematic for your amp but in general, tube amps use voltages many times in excess of 400 vDC and the power supply filtering caps can store that voltage even if the amp is off and unplugged.
So either learn how to safely discharge those caps or take it to a reputable tech to have it serviced.

+1 on the pre amp tubes and possibly the relay. Might be a bad wire/switch in the footswitch though. Id definately like to try another footswitch first if it was mine. I wouldnt buy one-probably schlep the amp to GC and try one of thiers. Bob

[mattball826]

Preamp tube. Are the remaining ones original? Bugera users say to change them all. Originals are not that good to begin with.

[MaxGrove]

yeah, i changed all of the pre-amp tubes at once. not using any bugera tubes at all anymore. i took apart the footswitch and looked around (i do alot of soldering and small electronic work like that) but i didn't see anything disconnected in the pedal itself. I'll check the relay inside the amp tonight for that.

When i tap the tops of the pre-amp tubes i can hear a tap through the speakers on 2 of the 4 but the others don't seem to make much sound at all. there was no change in the problem from before or after replacing the tubes.