Bias pot location...

[Jeph]

I'm going to put an accessible (from the outside) bias pot on my build. Ideally, I'd like to put it way over in no man's land (back of the chassis, lined up with v1/v2. Is there a problem with running wires this far?

[UR12]

hey Jeph

Are you going to install any test points so that you can measure the bias from the outside also? You should be OK as long as you use good lead dress and keep them down on the chassis.

[Jeph]

Thanks Dana, yeah, I'm putting in test points as well. Gimme a sec, I'll post a pic so y'all with a clue ( ) can tell me yay or nay on the location.

[UR12]

You might want to use a 10 turn knob on your pot so that if it gets bumped or something it won't send you tubes into meltdown.

[Jeph]

I'm going to look around for a locking pot tomorrow. If I can't find one I'll be sure to go with a multi turn pot. Here's where my test points and pot will go:

[UR12]

Jeph

I can't tell from the picture you posed what location you are planning on using. Did all of the picture come through?

[Jeph]

I think, it works for me? If you can see the bias test jacks, the bias pot will go to the left of them. How much of the pic do you see?

[UR12]

just your preamp board and a little to the right of it. the image is about 2" tall and full width on my screen.

[Jeph]

How's this?

[img768]http://www.chassi-swing.com/amps/expres ... cation.jpg[/img]

[UR12]

Yea much better! Where are you going to run your ground for the pot. You might try grounding it on the lug on the power tube where 1 and 8 are grounded.

[Custom 100]

Go big and add a ten turn pot and a locking adjustment knob ala Komet:

NTE-505-0004 462 DIAL 1 X.25 10 TURN

CLAROSTAT 73JA 50K

I think Allied and Digikey carry the pots. Not sure who has the locking knobs.

Hope that helps

[Elcabong]

The Bourn 3590 precision pot. is another option. It can be installed with the Bourns precision-counting dial. I found them a E-Sonic, part 3590S-2-503 for the pot and H-22-6A for the metal dial.

[Jeph]

That's pretty much what I ordered from Mouser. I also ordered a couple locking pots from surplussales.com so I can try different stuff.

[truamp]

Jeph,
I'm starting to procure my parts and I'd like to add bias test ports like you have in your build. Will you help me out and tell me where you sourced your bias test ports and what the associated part numbers are for the black and red ports? Thanks!

Art

[Jeph]

Sure thing.

Mouser part #s:
565-3542-3 - Orange
565-3542-8 - Gray