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Old 10-16-2013, 11:31 AM   #1
pedalmike OP
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Replace Twinmax Potentiometer

Wondering if anybody on the forum has expertise or experience in replacing the zero adjust potentiometer on a Twinmax. I tried deoxit but I can't make the existing potentiometer work...it makes the scale needle jump wildly from one end to the other...i can't get it to zero.

I think I could replace it myself if I could find the part. This one mounts to the PC Board with soldered lugs rather than the panel.

Let me know if you have any ideas.

Thanks.
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Old 10-17-2013, 08:24 AM   #2
Terry
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I could certainly help you out. Getting the replacement part might be the hardest part, but pots are usually pretty available. Can you post a pic?

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Old 10-17-2013, 12:42 PM   #3
Guy Young
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Quote:
Originally Posted by pedalmike View Post
Wondering if anybody on the forum has expertise or experience in replacing the zero adjust potentiometer on a Twinmax. I tried deoxit but I can't make the existing potentiometer work...it makes the scale needle jump wildly from one end to the other...i can't get it to zero.

I think I could replace it myself if I could find the part. This one mounts to the PC Board with soldered lugs rather than the panel.

Let me know if you have any ideas.

Thanks.
I replaced both a couple of years ago. They were "dead" when I went to pull it out to use it.

I selected some linear taper pots normally used in a guitar with the same ohmic value of the ones in the Max. I had to add a couple of short leads to connect the pots to the PC board, and IIRC, had to enlarge the holes slightly so the pots would fit in the box.

I'll see if I can find the paperwork where I bought them.

.
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Old 10-18-2013, 09:39 AM   #4
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Thanks Terry and Guy.

Terry, I'll take a photo or two and post them first chance I get.


Mike
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Old 10-18-2013, 11:33 AM   #5
Guy Young
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Quote:
Originally Posted by Guy Young View Post
I replaced both a couple of years ago. They were "dead" when I went to pull it out to use it.

I selected some linear taper pots normally used in a guitar with the same ohmic value of the ones in the Max. I had to add a couple of short leads to connect the pots to the PC board, and IIRC, had to enlarge the holes slightly so the pots would fit in the box.

I'll see if I can find the paperwork where I bought them.

.
I have looked, but can't find the paperwork from when I ordered them.

You'll play hell trying to find the PCB mounted types that are in there, that's why I went with the panel mounted types. The ohmic value is stamped/printed on the body of the pot. You'll need to get a short, split shaft to accept the push-on knobs.

My apologies; wish I could be of more help.

.
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Old 10-18-2013, 05:51 PM   #6
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Here are a few photos of the pot





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Old 10-18-2013, 06:02 PM   #7
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Guys:

what do you think of this pot? Closest I've been able to find so far.


http://www.tubeampdoctor.com/product...nt&language=en
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Old 10-18-2013, 06:27 PM   #8
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I don't think I'll be able to find one closer than this.

http://www.mouser.com/ds/2/13/TW-700149-186104.pdf

B100K, Linear taper, even the mounting lug dimensions and the three solder terminals are the same dimensions as the one in the twinmax. It is a 'D" shaft instead of a serrated shaft...who cares? $2.07 each at Mouser Electronics.

Let me know what you think...looks like it's worth a try.
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Old 10-18-2013, 06:32 PM   #9
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Twinmax repair

3 years ago, Paul Weis at Cal-Moto (paul@calmoto.com) was kind enough to ship me (at my shipping cost, only) a dud twinmax, returned under warranty, so that I could pull a pot to replace one of mine that failed. He was impressed that anyone would bother to repair rather than replace. It worked. I thanked him. It might work for you.
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Old 10-19-2013, 08:27 AM   #10
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Quote:
Originally Posted by pedalmike View Post
I don't think I'll be able to find one closer than this.

http://www.mouser.com/ds/2/13/TW-700149-186104.pdf

B100K, Linear taper, even the mounting lug dimensions and the three solder terminals are the same dimensions as the one in the twinmax. It is a 'D" shaft instead of a serrated shaft...who cares? $2.07 each at Mouser Electronics.

Let me know what you think...looks like it's worth a try.
Looks good. You can always find a knob to fit at Radio Shack.

Good find!

.
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Old 10-19-2013, 08:29 AM   #11
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This one from digikey looks close too.

http://www.digikey.com/product-detai...2257-ND/203836


If you aren't comfortable with the soldering, and can't find someone near you to help, I'm glad to do it for you.

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Old 10-19-2013, 03:47 PM   #12
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Thanks, Terry. That's a nice offer. I have a standard Weller electric soldering gun with two heat settings. Would that be OK to use to replace this pot?

Mike
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Old 10-19-2013, 05:11 PM   #13
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I'm not familiar with the Weller, but it will probably be fine. You will want to use solder-wick or a solder sucker to remove the old pot. It might make it easier if you just use a sharp wire cutter to clip out the old one and unsolder the remnants.

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Old 10-20-2013, 05:33 AM   #14
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I've been repairing PCB for years and also use a 2-heat range Weller as well as a couple of pencil irons. Never had too much luck with the solder wick so I've always used a solder sucker.

Just be careful with your heat so you don't lift the pads and/or traces from the board. Good suggestion to clip the old one out and remove the remaining bits separately. Also, make sure you use a rosin core solder when installing the new pot.

Best of luck with it and let us know how it works out.

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Old 10-23-2013, 09:57 AM   #15
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Well, I took Ventusa's advice and called Paul Weis at Cal Moto. He had another non-functioning twinmax that he is sending me at no charge other than shipping.

I'll let everybody know what happens.

Thanks again.

Mike
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