Bias pcb

[Valvehead]

Can this be modded to work with Usa voltage = 120vac input ? If so, what would you change ??

[nickb]

Can this be modded to work with Usa voltage = 120vac input ? If so, what would you change ??

The transformer determines the power line voltage. Chances are you already have one. What is the make and model of the target amp?

[Valvehead]

its a Bugera 333XL Infinium . The "infinum" bias supply has gone south and i cant buy a new pcb. i thought maybe i can bypass that and use something like this. i was just concerned about the input acv on that scem

[nickb]

I sure something couldbe done to bypass the control PCB but without a schematic for it threre's no specific direction I can give you. You would probably have quite a bit or surgery to do. I would go for a simple scheme that drives each tube with the same bias voltage. There will be some kind of bias supply already that you could use.

You original question suggests limited knowledge and too would be a handicap.

[Valvehead]

I know there would be surgery..i thought this route may be easier

cant seem to upload the schematic here

[nickb]

The upload does work. It just looks like it doesn't. It seems work better when you use advanced settings. Give it another go as it would be a huge help

[Valvehead]

it wont let me upload a pdf. Thats all i can find = a 333xl NON Infinium scem online anyway

[nickb]

I have that one. It's rumored to have many similarities but without the bias control PCB. Are you able to trace out the wiring from the transformer for the negative supply? Do the same for the circuit around the output tube grids. Also look in the cathodes and there might be MOSFET and current sensing resistors in there.

[Valvehead]

ok--will have a look .