GK B50K Pot Replacement

Started by HecticArt, July 25, 2016, 10:02:03 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

HecticArt

I'm looking to replace the volume pot that came with my GK internal kit.

Long story short, I finally got around to removing the GK-3 from my new guitar to install the internal kit. (Committing to the locations that I was going to carve into the body took me a little while.)

Everything went well until the very end. I over-tightened the nut on the volume pot, and broke the shaft off of the body. (I honestly don't think I gave it that much force, but things happen I suppose.)

While I'm looking for a B50K that will fit, I was wondering what will happen if I use a different value pot until the 50K arrives. I have some old volume pots that I've removed from other guitars that I was wondering if they would work while I'm waiting for UPS. I haven't looked yet, but I'm guessing are in the neighborhood of 250K.

I know many of you understand these details much better than I do. Is this a terrible idea? What kind of consequences could there be by loading a pot with a different value into this? Is there a range that should work OK on a temporary basis?

Amazon is striking out on B50K's and Radio Shack is a joke, so I'm guessing I'll have to order one from Roland. If it's not going to harm anything, or have goofy side effects, I'd sure like to use a temp to finish wiring the thing and put it back together again.

Many thanks!

Elantric

#1
Contact Roland

Roland Corporation U.S.
5100 S. Eastern Ave.
Los Angeles, CA 90040-2938
Customer Service Tel: (323) 890-3700

But any 50K Linear POT will work

Here are alternate sources:

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=50k+linear+guitar+pot


http://www.guitarpartsresource.com/electrical_minipots.htm
400-253
Aguilar 50k linear mini pot with center detente. 6mm split shaft with hardware. Requires 3/8" mounting hole.




https://reverb.com/item/1061736-wd-cge-50k-ohm-full-sized-split-shaft-linear-taper-pot?_aid=pla&pla=1&gclid=CjwKEAjw8da8BRDssvyH8uPEgnoSJABJmwYoXvQ7N8_phZ7GBna4h-KWbXx1BV6vk4-ivarroPEcwhoCsFDw_wcB

WD CGE 50K ohm Full Sized Split Shaft Linear Taper Pot - $9



QuoteWhile I'm looking for a B50K that will fit, I was wondering what will happen if I use a different value pot until the 50K arrives. I have some old volume pots that I've removed from other guitars that I was wondering if they would work while I'm waiting for UPS. I haven't looked yet, but I'm guessing are in the neighborhood of 250K.

I know many of you understand these details much better than I do. Is this a terrible idea? What kind of consequences could there be by loading a pot with a different value into this? Is there a range that should work OK on a temporary basis?

If you attempt to use a 250K pot - you will get a narrow usable control area -  within "0-3" on the GK Vol Pot

Its best to get the correct 50K Linear Pot

HecticArt

#2
Dang! I should have removed the "B" from my Amazon search!
It came up with some less than stellar results and a few that either let me place the order before saying that they were out of stock, or were coming from China and would be here next month.

I'll see how long it takes Roland to get one or two shipped, then revert to Amazon if need be.

As a followup to your note about the "0-3" for the higher value pot, does that mean it's essentially either on or off? Or does it mean a significantly reduced output? Basically, I'm looking to finish the wiring job to make sure I have everything done correctly. I can use another guitar or put the GK-3 back on for practices.

Almost forgot.
Thanks for the feedback!
It's much appreciated.

Elantric

#3
I would get the correct 50K linear pot
Quotedoes that mean it's essentially either on or off?
substituting a 250K will leave you with a  near on  / off experience confined to a 20 % rotation range on the lowest counterclockwise settings on the GK Vol Knob

HecticArt

Ahhhh. Gotcha.
I'll keep chasing down the 50.

I appreciate the "Intro To Electronics" tutoring.
My dad was an electrical engineer & teacher. He tried with me........ ;)

Thanks again!


mmmmgtr

If you strap a 60k resistor across the pot the effective resistance will be about 50 k. This sweep won't be linear, might be a little weird, but easy enough to experiment with.

HecticArt

35 years ago I knew a lot of the basics, ohms law, and whatnot. I still know what parts are what, what they do, and how to identify sizes. That looks like a good resource for a lot of the fundamentals.

Thanks!

HecticArt

Quote from: mmmmgtr on July 25, 2016, 03:02:13 PM
If you strap a 60k resistor across the pot the effective resistance will be about 50 k. This sweep won't be linear, might be a little weird, but easy enough to experiment with.

The thought of throwing a resistor on there crossed my head after Elantric posted his replies. It finally clicked. I've got a bunch floating around somewhere, but it will probably take me as long to figure out where they are as it will take for a new pot to arrive in the UPS. I still need to check through my box of salvaged guitar parts to see what values are on the spare pots I have. Who knows, I may get lucky. 

The feedback is greatly appreciated. It drives me nuts to have things in a dismantled state like that.

Elantric

QuoteIf you strap a 60k resistor across the pot the effective resistance will be about 50 k. This sweep won't be linear, might be a little weird, but easy enough to experiment with.

62.5k ohm in parallel with the 250K pot = 50k non-linear pot
http://www.sengpielaudio.com/calculator-paralresist.htm


gumtown

60k ohm across the 250k ohm pot will also have a strange result, the end to end resistance will be 50k, but the sweep in the middle range will still be up to 125k.
This will effectively give you 0-50% range in the first 20% travel, 50-100% range in the last 20% travel,
and a not much change in the middle 60% travel.

You can get anything on eBay
10 x 50k ohm linear pots for 2 bucks
http://www.ebay.com/itm/10-pcs-50K-ohm-Linear-Taper-Rotary-Potentiometer-Panel-pot-B50K-15mm-/381374716268?hash=item58cbb4596c:g:BZsAAOxyfVtSLw7E
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

HecticArt

I only had 250's and 500's in my salvage parts, but the new 50's will be here Wednesday or Thursday.
I'll finish the wiring and make the new cover plate in the meantime. 

Thanks for the help.