Which dual ganged pot for Ken Fisher type 1 ppivmv in a 2X5881 cathode bias amp

[Bionic]

Want to order the part for my tech. The amp is a Z 28 front end with 2X5881 cathode bias power

[SILVERGUN]

Alpha Dual amp pots - 1ma


Tube Amp Pots, Amp Knobs , Guitar pots (hoffmanamps.com)

[Latole]

Don't you find it strange, not to say worrying, that your "tech" doesn't know which pot to order?

I am not sure that I would give him my amp to repair.

Be careful......

[2deaf]

What is the value of the current grid leak resistors?

What kind of phase inverter do you have?   

[Bionic]

Thanks everybody, I figured I would order the parts and then have him install them but maybe I should just give it to him and let him source the parts. It was just a crossing off my list type of thing. It is a based on a Dr z Z28 so I will check to see what the values of the grid leak resistors. The phase inverter is a 12ax7

[2deaf]

I think it has a LTP phase inverter and 100K grid leaks.  If so, a Trainwreck Type 2 with a 100K audio dual pot might be more appropriate.

[Bionic]

So a Lar Mar ppivmv will do the trick? I think Lar Mar is type 2 but with protective resistors in case of failure

[SILVERGUN]

Here's a helpful link, and the info you are looking for is about halfway down the page:
https://robrobinette.com/The_Trainwreck_Pages.htm

[2deaf]

It is a based on a Dr z Z28 so I will check to see what the values of the grid leak resistors.

Any luck looking at those resistors yet?

[MFowler]

They should be 100k with 6v6 as Doc built the circuit, with 6L6 maybe he increased to 220k.

[BrianS]

Nothing to say about the circuit, but as a full time repair tech, I suggest letting them source the parts.