Bypassing broken gain pots

[Jonny Hotnuts]

I have this idea of bypassing a broken gain pot by removing it and using a resistor of approximately 50% of the pots range to permanently set the gain at 50%.

I would not mind changing the pot but I have never seen one like this (small green and 6 legged) if I could find a direct or equivalent replacement.


So is this a crazy idea or are the pots around?

[gtforme00]

Sounds like a solid plan. Those pots all have low power ratings, you could use any 1/4 or 1/8 watt resistors in their place. I have searched for these multi-gang pots in the past without luck, maybe someone will come along and show us a source. That failing, you have a very reasonable approach and one that I am considering taking if I cannot clean a pot on an old MTX I have.

Regards,
David

[I Am An Idiot]

Johnny, the resistors will work fine as long as the center leg of the pot is electrically connected to one of the outer legs. They may be using the pot as an actual potentiometer, if this is the case you will need to use 2 resistors per each channel of the pot.

GT

To clean the pot on your MTX amp, try the following. You will have to remove the pot from the board. Go to a hardware store and buy a 1 inch pipe nipple 3 inches long. Get 3 PVC pipe caps. Drill a 3/16 inch hole in the center of one of the caps. Screw a pipe cap on one end of the nipple, drop the pot into the pipe, spray enough WD-40 into the pipe to cover the pot completely. Now screw the cap with a hole in it to the other end of the pipe.

Now using an air compressor and a blow nozzle, prefferably a blow nozzle with a rubber conical tip to make a good seal on the hole in the pipe cap. Pressurise the pipe several times. This will force the WD-40 into the pot. As soon as you remove the pot from the WD, you must turn it from stop to stop several times, this will use the wiper of the pot to clean the carbon on the control.

The third pipe cap is to seal the pipe and save the WD for your next project.

[theAnonymous1]

Do you know what value it is? Does it look like these.....

[Jonny Hotnuts]

Do you know what value it is? Does it look like these

Dont know what value......
THey have markings on the side that say:
5038 (or 503"B")
HF

[Jonny Hotnuts]

another pic

[I Am An Idiot]

They are 50K pots. I put a 50K resistor on my picture with the single resistor, it should have been a 25K to simulate the gain being in the middle.

[gtforme00]

Could you post a more clear picture of the pin side of the board and the dimensions of the pot body?

Looking at the ALPS catalog, I found this model number: RK097122100Y

Dual gang, 50k, 3B taper (log taper)

Seems to match the specs, but I can't find it for sale.

[theAnonymous1]

Originally posted by gtforme00
Could you post a more clear picture of the pin side of the board and the dimensions of the pot body?

Looking at the ALPS catalog, I found this model number: RK097122100Y

Dual gang, 50k, 3B taper (log taper)

Seems to match the specs, but I can't find it for sale.

The RK097122100Y has a switch. I don't see any 503B switchless pots in the RK097/98 series. It might be a custom job.

[MatthewS]

Just gotta dig a little at the japan site.

RK09712200FS

And mouser lists them, but they are non-stocked..

Alps catalog page with part ->

http://www3.alps.com/WebObjects/cata...K097/RK097.PDF

Good luck!

- Matt