Bias Trim Pot wiring ?

[gtrplayr1976]

Ok..I would like to know if I have this bias pot wired correctly. I was told to solder the wiper to one tab , wire that to a 5K resistor, and then to one hole where the bias resistor used to be , then wire the other tab to the other hole. Is this correct ? My problem with that was that I wasn't getting enough bias current so I had to increase the resistor to 20K.

Thanks !

[trem]

Not sure what amp you have. Sounds like you are set, although our terminology can be mislading....
I would put the Wiper to the grids of the power tubes. Maybe that is a pair of 220k resistors.?
One end of the pot goes to the negative voltage supply.
The other end of the pot has your "bias resistor", and that goes to ground. As you have found out, you may have to change that value to make sure you can get enough, or not as much bias voltage, depending on the tubes you install.
Good Luck

[gtrplayr1976]

Thanks trem, It's a Crate BV50H. Sounds like I may have it incorrect if all three leads have different paths. I may have read it wrong. Here are the schematics, and R80 is what I was told to replace with a trim pot.


29621P0_.pdf 29701H2_.pdf 29701H21_.pdf

[trem]

I misunderstood what you have taken on here. Now I am kind of confused.
So you are replacing R80 with a trim pot.
Sorry about that..... It sounds like you have already found the right values to make it work. Did not realize what amp you had.

[gtrplayr1976]

Yes. R80. My confusion now is where the three leads from the pot go. Thanks for the replys.

[pontiacpete]

I think you should hook up only two of the tabs, the wiper and one of the end ones and leave the other free. You can check if you have it right by clipping your ohm meter up and turning the pot, you should see it go from very low ohms up to 20k.

[gtrplayr1976]

That's the way I did one of the other others I have , but also someone had said to solder the wiper to one of the leads. It has seemed to work either way ,but I want to try to get it right.

[pontiacpete]

YOu can use either end of the pot but not both ends

[gtrplayr1976]

Thanks ...I will make the change. Could that cause unwanted noise issues ?