GML 8200's pots

[distorter]

Hi, recently I noticed the pots on my GML 8200 had gone bad. Especially the "3-deck freq/q control" and "4-deck freq/q control with shelf switch"
I emailed GML and they offer extremely expensive prices...


Does anyone know if I can find these pots elsewhere?



Thanks!

 

[beatnik]

GML are well known to charge extortionate prices for spare parts.
Perhaps to also justify the very high price of the final products...

I can see the pots are hold together by a screw. If they are just scratchy because of dirt it should be straight forward to take apart and clean them.

If on the other hand the conductive track is damaged and you need entirely new pots, the only companies I know that would make custom pots in single pieces are Omeg and Blore-Ed in the UK.

 

[emrr]

A-B Mod pots. Much debate with no great answers in the distant past. You’ll find threads here. They became extremely expensive to order at least a dozen years back, memory says those quotes above aren’t severely inflated.

 

[jensenmann]

Unfortunately they have a unique footprint which makes it difficult to replace them with something else.

 

[beatnik]

If I'm not mistaken there is a Bourns that has the same footprint, and the sections are compatible with the Allen Bradley

With those prices it would be cheaper to buy single pots take them apart and replace the sections on the original GML pots.

Although on your photo I am seeing a C50-something which probably means rev log, and it has a switch. That one might be difficult to sort out.

But first of all - have you tried cleaning the original pots ?

 

[zamproject]

I have hundred of those AB sealed pot in my desk, virtually they can't take dust, the conductive track can become noisy at sliding when not used often, especially at the spot you let them too long, that's why I always reset them to full CCW when I reset the console.
I open some long time ago but don't remember if it's possible to retention the wiper brush.
The solution that work fine for me when one was not used since long time is to move them fast, full travel, for few second, and the noise disappear.
I'm not 100% sure but for the moment I identify this issue as a local deformation/depression of the substrate where the wiper sit (too long) causing less contact efficiency.

Cheers
Zam

 

[FIX]

The front two are 100K reverse audio taper, the rear one is 5K linear. Front two are freq, the rear is Q.

If you can get them apart far enough to get to the element, you can clean them off and spread the wiper contacts a little so they find new area. Exacto knife blade... If they are single wiper, you can bend them slightly so they are on new area. Try with a pot of any value first... Check Alibaba too... Conductive plastic (white square) can wear, but not as fast as carbon (brown square). If you can buy single pots somewhere, you can replace the cups.

 

[saint gillis]

Datasheet : https://www.potentiometers.com/pdf/Catalog70.pdf

Cut Boost is 50K linear with center tap ( 70A4N040P5033 )
The EQ / Q combo is 2 x 100K rev log for the frequency and 5K rev log for the Q, for the 2 bands with a shelf there is an added switch

 

[Ike Zimbel]

I have a complete Mod-Pot kit kicking around, I will check and see if I have any of those values left. I may not have all of them, but since they are modular...you could at least replace some of them.