Gallien Krueger potentiometers

[MarkusBass]

I'm looking for potentiometers for an old Gallien Krueger MB150E amp. I think that at least 4 or 5 of them need to be replaced.

[g1]

Full Compass?
Gallien-Krueger Replacement/Service Parts | Full Compass

[The Dude]

Can we get pics of the whole pot?

[MarkusBass]

Of course but I can do it tomorrow in the evening. It's getting late and it's quite difficult to get access to the pots.
Anyway, it seems that they look like this one: Gallien-Krueger 070 2503 B 50K Ohm Pot B For MB150E | Full Compass

Mark

[The Dude]

Yep. g1 snuck in while I was typing. No need for pics if you already found what your looking for.

[nevetslab]

Considering you will have to remove the PCB assembly to get the pots removed, you might consider opening up the pot by carefully prying the four folded tabs of the cover up, lifting the cover off, then cleaning and re-lubing the resistance track and put the cover back on, folding the tabs back into place. I do that all the time and, unless the resistance track is really buggered, they come back up nice and quiet and last a good length of time. Now, on two or more gangs, you can't get the front and middle covers off...only the rear cover. In those cases, I carefully brush in Caig DeOxit (as opposed to spraying it in), and you just exercise the control a bunch, and they're good to go.

[MarkusBass]

It appears that the pots are of different type - without supporting bracket. I may try to fix one or two of them (thanks Nevetslab) but three or four need to be replaced (one has broken shaft).

[nevetslab]

Just in case, I pulled apart one of the pots I have that has supporting brackets. The bracket doesn't come off on this version (they do on Fender's pots), but the four tabs of the cover still appear at the front, so I got the cover off just fine, exposing the wiper & track for cleaning. I use brush-on Caig DeOxit 5. Essential tool needed are small flush-cutting diagnol cutters. This tool shown is an Erem 71AE 45 deg angle flush cutter, which is perfect for this task...used to slip in and pry up the cover tabs. Closing the tabs back down is easy with needle nose pliers.

[TimmyP1955]

For cleaning PC mounted pots:

Put two cleaner "straws together end to end and connect with heatshrink, then seal the ends of the shrink with superglue.

Find a guitar string that just fits into the straw.

Heat one end of the straw until it's pliable but not melty. Push the guitar string into the straw about 2", and bend the end of the straw 90 degrees with as tight a radius as you can manage.

When the straw has cooled, pull the string out.

Why the string? It keeps the straw from kinking and thus becoming blocked.

With this, you can get under the pot and shoot cleaner up into it. I prefer CRC QD Electronic Cleaner.

[g1]

I put a piece of heatshrink on the cans straw, and shrink only the connection. So I now have a heatshrink extension on the straw. Now I strip a piece of twist tie or take a piece of tag wire and insert it in the heatshrink, pushing it all the way in and just a touch more.
Now I can bend the extension to anything I want at any time.

[MarkusBass]

Thanks for the tips but for me it was easier to desolder the pot (and the input jack), dissasemble the pot, clean it, assemble back and solder back:


The potentiometer works correctly now. But I'm still looking for the other pots.

BTW, it looks like the amp had some serious problems:

[g1]

I think you may have to use the newer pots and just snip the support brackets off. The dual pot they have does not have the support bracket. The one with the plastic knob does have it, as does the one in your amp.

[MarkusBass]

OK, the pot worked great for two days but now it doesn't . I have to buy a new one. But I noticed that the pots at fullcompass are different than I need.
This is the one I need:


This is the one available at fullcompass:

Please look at the shaft.
I also emailed GK but there is no answer until now.

[Leo_Gnardo]

OK, the pot worked great for two days but now it doesn't . I have to buy a new one. But I noticed that the pots at fullcompass are different than I need.
This is the one I need:

I think Mouser may carry pots similar or identical to the GK in your photo. Search Alpha, 16mm, knurled shaft (yes I know it's spline but that's what they call it.) Mouser p/n 313-1530F-250K for instance. I bought a few about 3 weeks ago.

[g1]

When you say shaft do you mean the threaded portion of the bushing, and the distance it will be stood-off from the faceplate?
You may have to rig up spacers for that.
Still no reply from GK I guess?