Pot replacement question

Nooblett · #1 10-20-2010, 03:33 PM

So i have a cobra bass (greg bennett design samick), it's an active bass and ever since i've bought it i've had to 'flick' the treble knob to get a good sound out of it (got it in a pawn shop for a pretty low price), and its slowly been getting worse and worse until now where i have to flick it a bunch until it'll finally stop making this scratchy sound.

I tried to clean the pot, no effect, used contact cleaning fluid and everything, my next guess (i'm not exactly an expert on pots) was that the contact on the bottom wasn't being well made (see picture), so i tried to ghetto rig it by soldering it (just so it could hold in one position until i could replace it), no effect, so now i know that the only fix is to replace the pot.

My question is, on the picture below, the pot has what appears to be 6 connections to the circuit board (so two rows of 3 connections, see pic), most of the 250k pots ive seen online only have 3 connections... The pot is labelled MN250k, and i've managed to find a few online but it looks like i'll have to do some funky wiring to connect the new pot to the board.

I've spent quite a while trying to find a replacement pot that would be perfect for this, but i'm at a complete loss...

i'd absolutely love any help i can get here, i'm planning on getting a new bass this winter but i'd like to have this one last till then.

Thanks!!

**Syco_bass** · #2 10-20-2010, 03:44 PM

Is this a duall "stacked" pot for bass and treble?

Nooblett · #3 10-20-2010, 03:47 PM

Nah, it's just for the treble. there's a separate pot for the bass, and 2 more for volume control and pickup balance.

SGD Lutherie · #4 10-20-2010, 04:22 PM

It's a dual ganged pot.

Try using WD-40 to clean it. If that doesn't work, nothing will.

It could also be a bad solder joint.

Nooblett · #5 10-20-2010, 04:39 PM

Quote:

Originally Posted by SGD Lutherie

It's a dual ganged pot.

Try using WD-40 to clean it. If that doesn't work, nothing will.

It could also be a bad solder joint.

I used WD-40 already :$, it was one of the first things i read about using online, which is why i now think that theres just something wrong inside of the pot. I could try to redo the solder joints though... think thats worth doing?

SnakeKappele · #6 10-20-2010, 04:45 PM

It is a 250K Ohm blend pot.

I think you have something like this:
http://www.guitarjonesusa.com/images/5401_dia.jpg

Are you sure you have the right pot?

I'd use Deoxit or a tuner cleaner instead of WD-40.

OldHack · #7 10-20-2010, 05:27 PM

You should be able to get the pot from here www.mouser.com

Nooblett · #8 10-20-2010, 06:30 PM

Quote:

Originally Posted by SnakeKappele

It is a 250K Ohm blend pot.

I think you have something like this:
http://www.guitarjonesusa.com/images/5401_dia.jpg

Are you sure you have the right pot?

I'd use Deoxit or a tuner cleaner instead of WD-40.

I have something that looks exactly like this :

which looks pretty damn similar

And i should have the right pot... I bought this in a pawn shop about a year ago so it's possible that someone tried to replace it with a bad pot but i doubt it.

And I could try a different cleaner but i just feel that it wouldn't do much good since rubbing alcohol and wd-40 didnt do anything, i think the inside of it is what's bad, not the contacts on the outside (could be wrong).

Quote:

Originally Posted by OldHack

You should be able to get the pot from here www.mouser.com

Thanks i'll try to look around there, might take me some time though considering they have so many pots

edit: http://www.mouser.com/Passive-Compon...5g9h?P=1z0x8a8

none of the 250k pots look like what i need, is this thing really hard to find or am i just not looking in the right places?

SnakeKappele · #9 10-20-2010, 07:04 PM

Quote:

Originally Posted by Nooblett

I have something that looks exactly like this :

which looks pretty damn similar

And i should have the right pot... I bought this in a pawn shop about a year ago so it's possible that someone tried to replace it with a bad pot but i doubt it.

And I could try a different cleaner but i just feel that it wouldn't do much good since rubbing alcohol and wd-40 didnt do anything, i think the inside of it is what's bad, not the contacts on the outside (could be wrong).

Thanks i'll try to look around there, might take me some time though considering they have so many pots

edit: http://www.mouser.com/Passive-Compon...5g9h?P=1z0x8a8

none of the 250k pots look like what i need, is this thing really hard to find or am i just not looking in the right places?

What I meant was I think you are working with the blend control and the treble is on the left in your picture.

OldHack · #10 10-20-2010, 07:17 PM

Shouldn't have to order all the way from AU to get one but it looks like they have them here: http://evatco.com.au/pots.htm

that is, if it is actually the dual gang that you need

SGD Lutherie · #11 10-20-2010, 07:39 PM

Quote:

Originally Posted by SnakeKappele

It is a 250K Ohm blend pot.

I think you have something like this:
http://www.guitarjonesusa.com/images/5401_dia.jpg

Are you sure you have the right pot?

I do believe you are correct! I couldn't imagine why the treble control needed to be a dual gang pot.

I didn't see that he said it's marked MN250K. That is a blend pot (M/N taper, 250K).

Quote:

I'd use Deoxit or a tuner cleaner instead of WD-40.

Here's why I suggested WD-40. I have a Behringer mixer, and about 10 years ago I spilled Pepsi on it. So a few of the faders were in not very good working condition. I tried everything made for cleaning pots, including opening them up and cleaning the traces with water, and nothing worked. Then I tried WD-40, and they were almost as good as new!

Since then I have used it on stubborn pots that don't respond to stuff like Deoxit. Most tuner cleaners are real junk.

Nooblett · #12 10-20-2010, 07:57 PM

Quote:

Originally Posted by SnakeKappele

What I meant was I think you are working with the blend control and the treble is on the left in your picture.

the treble is actually on the right in my picture (its the golden one)

Quote:

Originally Posted by SGD Lutherie

I do believe you are correct! I couldn't imagine why the treble control needed to be a dual gang pot.

I didn't see that he said it's marked MN250K. That is a blend pot (M/N taper, 250K).

Here's why I suggested WD-40. I have a Behringer mixer, and about 10 years ago I spilled Pepsi on it. So a few of the faders were in not very good working condition. I tried everything made for cleaning pots, including opening them up and cleaning the traces with water, and nothing worked. Then I tried WD-40, and they were almost as good as new!

Since then I have used it on stubborn pots that don't respond to stuff like Deoxit. Most tuner cleaners are real junk.

Yes, a blend pot is exactly what is it, but the next problem is that i can't find a blend pot that would fit in that spot nicely, as in, it has the connectors in the same 'arrangement' as the one i already have, i could probably any other one to work, but i'd have to take wires and connect the wires to the board and then to the pot.

So, all the blend pots im able to find look like this:

and i think something like that would work but i'd have to use a bunch of wires and put those in to the board then connect them to the connectors of the pot. would that be the best plan? cause finding a blend pot made for a circuit board could be really tough

thanks for all of the help guys its really appreciated!

SnakeKappele · #13 10-20-2010, 08:07 PM

Quote:

Originally Posted by Nooblett

the treble is actually on the right in my picture (its the golden one)

The pot on the right is a 250K Ohm blend pot. The other three are standard sweep pots.

Can you give a picture of the bass from the front and describe what you think the controls do?

Everything I know tells me you are working on the blend pot, not the treble.

SnakeKappele · #14 10-20-2010, 08:09 PM

As for the blend pot, I haven't been able to locate one with that type of PC mount yet.

SnakeKappele · #15 10-20-2010, 08:55 PM

I have hit my search limit

The best I can offer is to buy this preamp and scavenge the pot from it. It's expensive but you should have a bunch of spare parts from it.

http://www.guitarjonesusa.com/catalo...on=show_detail

Nooblett · #16 10-20-2010, 09:08 PM

Quote:

Originally Posted by SnakeKappele

The pot on the right is a 250K Ohm blend pot. The other three are standard sweep pots.

Can you give a picture of the bass from the front and describe what you think the controls do?

Everything I know tells me you are working on the blend pot, not the treble.

ah yeah sorry good catch. i'm working on the pickup balance knob, which is the blend pot, got the two mixed up.

yeah you're right, the faulty one is the pickup balance, the treble, bass, and volume knobs are completely fine.

a lot of the posts so far suddenly make a lot more sense :$

SnakeKappele · #17 10-20-2010, 09:23 PM

Quote:

Originally Posted by SnakeKappele

I have hit my search limit

The best I can offer is to buy this preamp and scavenge the pot from it. It's expensive but you should have a bunch of spare parts from it.

http://www.guitarjonesusa.com/catalo...on=show_detail

^^^^^^^^^^In case you missed it ^^^^^^^^^^^^^^^

Nooblett · #18 10-20-2010, 09:38 PM

Quote:

Originally Posted by SnakeKappele

I have hit my search limit

The best I can offer is to buy this preamp and scavenge the pot from it. It's expensive but you should have a bunch of spare parts from it.

http://www.guitarjonesusa.com/catalo...on=show_detail

Quote:

Originally Posted by SnakeKappele

^^^^^^^^^^In case you missed it ^^^^^^^^^^^^^^^

yeah thanks i did miss it :$

I could do that... i might end up doing it if it'd be way too messy to use a pot that looks like a picture i posted earlier (not built for a circuit board). i can think of how to do it, it might just be a bit messy with a bunch of small wires everwhere

thanks for the link!

SnakeKappele · #19 10-20-2010, 09:43 PM

Quote:

Originally Posted by Nooblett

yeah thanks i did miss it :$

I could do that... i might end up doing it if it'd be way too messy to use a pot that looks like a picture i posted earlier (not built for a circuit board). i can think of how to do it, it might just be a bit messy with a bunch of small wires everwhere

thanks for the link!

The other problem is mounting the pot. The original is held to the board by the lugs. If you mount it to the board, the nut could get in the way of seating the board in the bass and the shaft may not be long enough.

Nooblett · #20 10-20-2010, 09:49 PM

Quote:

Originally Posted by SnakeKappele

The other problem is mounting the pot. The original is held to the board by the lugs. If you mount it to the board, the nut could get in the way of seating the board in the bass and the shaft may not be long enough.

Yeah that'd be a real bummer, and there's not much of a way to make sure that wouldnt happen before buying the pot right?