Problem with bugera333-212 combo

  1. #1 by Krzysztof Rymarski on 03-21-2018
    Krzysztof Rymarski's Avatar
    Posts: 1

    Problem with bugera333-212 combo

    Hi,
    I have problem with my old bugera. This amp was bought in 2009-2010. I don't remember exactly. I found the same problem on the youtube:
    https://www.youtube.com/watch?v=QAKpbbRIbTY

    This strange noise occurs all the time. Doesn't matter if I have unplugged guitar, all eq sections/volumes/master volume etc. set to the 0. None of tubes is broken(visually) or microphonic. Wires, and capacitors looks fine. So the greatest probability is that something is wrong with power amp section. I have to add that main fuse sometimes blowing up. And here my questions:

    1. which tubes are connected in pair(inner and outter, other configuration)? I want to check if one of the tube is bad or more. I know that it will change the impedance (so I have to switch 8Ohm to 4Ohm ). I don't have schematic for this amp or layout, that's why I'm asking.
    2. Are they some known issues with this amp? Maybe repairing one of those will fix my problem
    3. Maybe bad biasing.. It can cause this problem?
    4. I want to check with multimetr unplugged tubes and after that bias with plugged tubes . Can you provide me biasing voltage for 6L6GC model?
    5. Any other suggetions how can I solve my problem?
    6. Bad or damaged socets for tubes?

    I want to ask before I will start repairing this amp. Less effort to find the solution. I don't want to send it to service - not cost effective. Probably sending this amp and service will be more expensive then buying new one.

    Best Regards