Replacement volume knob issue.

mattyfez

mattyfez

mattyfez

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12 Apr 2007
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Hey all,

Not sure if this would be better in the HiFi forum, but I guess it's more of a general electronics question.

Basically I have an old guitar effects unit, which is a rack-mount pre-amp for all intents and purposes. Its out of production and well out of warranty.

It works 100% fine apart from the volume knob, which takes a lot of fiddling to get any sound at all, or crackly sound. if its in just the right position it works fine with a clean sound. I've tried giving it a good spray with some iso alcohol to maybe clean it a bit but its made little difference.

So I figure I need to rip the volume pot off, and solder in a new one.
It looks to have 6 pins soldered onto a little PCB, whos only purpose is seemingly to feed into a 6 wire ribbon cable.

I know nothing about this sort of stuff but it looks like an easy job..

My question is, what's commercially available that's good quality? maybe somewhere like maplins? or something more audio specific?

I cant see any markings on the volume unit, so not sure if there are different types/resistance etc.

Some pics below, thanks for any tips...

20130623_190032_zps6dcae730.jpg



20130623_185957_zpsbbcd79db.jpg


20130623_185930_zps87804d83.jpg
 
Ok thanks that's some food for thought, I might drop the manufacturer an email and see if they can suggest something, as like you say I'm not sure if it has to be a particular resistance.

It doesn't look like a special part, I just want to get the bleeding thing working properly again! hah.

Thanks
 
neodude said:
It wouldn't really need to match the PCB. That's why god invented wires ;)
Click to expand...

well yes, the pcb doesn't seem to be there for any reason, so if I can just source the correct type of knob, I can get it soldered onto the PCB or straight onto the ribbon cable without much hassle.
 
jumpy said:
Could just be lack of use/dirt - get some contact cleaner and spray it into the pot then work the knob back and forth through its full rotation for 5 min - you really need to work the dial a couple of hundred times, not just wiggle it a little bit.. Cheap fix from a guitar tech/repair guy on youtube (davey4557).
Click to expand...

That's exactly what it is I think, lack of use, it's basically been sat in the cupboard for about 10 years but its quite an expensive bit of kit so I want to get t fixed.

I have used some pure alcohol/contact cleaner although I've not wiggled it a hundred times, maybe I just need to work the knob more :o, but the 'volume unit' doesn't have many holes in it so I wasn't sure if it was worth messing with.

But I'll attack it a second time with some more pure alcohol. I've also sent the manufacturer an email so I'll see if they can recommend anything.

Thanks for the advice so far :)
 
Tealc said:
The top two contacts in the last image are routed to ground, which is a common connection. Ground will be a whole ground plane within the multilayer PCB. It works well like this and PCB often have several ground planes. The middle two contact are connected top the wiper of the potentiometer. The bottom contacts are where the inputs are connected.
Click to expand...

Ahh thanks for that, so the top two aren't there just for show! I didn't think the PCB would be multi layered, but then I'm not well up on these things! Cheers :)
 
We are kinda going off topic here, we are talking about a broken volume pot, not how to improve the transient vibrations of molecules through the medium of thought and prayer. ;)
 
I've actually found a direct brand new replacement on the bay, for 14 bucks, plus shipping it from the USA will end up quite expensive. it's listed as "Digitech Output Potentiometer volume pot for many units GSP2101 2112 2120"

Seems a lot for a basic knob though, and it doesn't list any tech specs, which is annoying as I cant just spec up a similar thing locally.
 
Good news! Jumpy was bang on the money...

Got a reply from the manufacturer: "In the USA, call 801-566-8800 and ask for Digitech parts to order pot # 40-2011. You may also try spraying your 2101 output pot with DeOxIt, available at most electronic stores."

I interpreted this as 'drench it in solvent' and 'give it some welly'

I've given it a good clean with some surgical spirit, soaked into a bit of towel to try and squeeze it into the openings in the vol pot (and lot's of knob twisting) without actually removing or de-soldering anything.

It's a million times better, there's still a little bit of crackle when adjusting the knob, but when the knob is stationary, it sounds clean as a whistle, it works almost perfectly! I think another treatment or two and it will be spot on :D
 
Hmm, surely if one was concerned with 'micro vibrations' they should just remove the knob altogether so they are just left with the metal stump.

Less chance of any decorative additional knob vibrations that way surely?:D
 
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