Distortion Generator potentiometers

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X100Ver10
Posts: 83
Joined: Mon Sep 18, 2017 2:49 pm

Distortion Generator potentiometers

Post by X100Ver10 » Wed Dec 20, 2017 6:57 pm

I am trying to resurrect a Distortion Generator. The 5 slide potentiometers and the 2 switches seem to work OK after using some Deoxit D5 spray on them, however, they look like crap (rust, pitting) and I would like to replace them. I found and ordered the 2 larger slide potentiometers from Mouser (Alpha part number RA2043F-20-10EB1-A100K).
The 3 smaller slide potentiometers are proving difficult, especially since I can't read the part numbers on 2 of them due to the rust. The one at location R212 (the one on the left) looks like it is showing B10K and indeed measures 10K. The ones at locations R210 & R212 (middle & right) both measure at 500K but the part numbers are unreadable. Can anyone verify the following for me?:
1) The 2 unreadable smaller slide potentiometers are B taper (linear) or A taper (Logarithmic).
2) Does it really matter whether I use B taper or A taper?
3) Part numbers for the potentiometers and/or switches.

I'm still researching the switches but it is not looking good. Just more Rockman obsolete parts. :x

Anyone know if there are any of the 3 smaller slide potentiometers or the 2 switches sold anywhere? I also have headphone amp battery springs for trade, if interested.

Thanks.
Last edited by X100Ver10 on Wed Jan 24, 2018 3:06 am, edited 3 times in total.

RockmanCentralBob
Posts: 240
Joined: Fri Feb 06, 2015 2:10 am

Re: Distortion Generator potentiometers

Post by RockmanCentralBob » Wed Dec 20, 2017 10:39 pm

500KB are what you are looking for, and yes, it matters.
It's not gonna be easy to find the sliders though...

X100Ver10
Posts: 83
Joined: Mon Sep 18, 2017 2:49 pm

Re: Distortion Generator potentiometers

Post by X100Ver10 » Wed Dec 20, 2017 11:00 pm

RockmanCentralBob wrote:500KB are what you are looking for, and yes, it matters.
It's not gonna be easy to find the sliders though...
Thanks for verifying Bob.

Bob or anyone. Is there any interest in getting new switches and potentiometers made for the headphone amps and modules? If we can get enough people to go in on it, we can probably keep our individual costs down. I know CW will make the switches, however, they seem to want a 500 minimum for each item. Cost prohibitive for 1 guy. Who's in? :)

X100Ver10
Posts: 83
Joined: Mon Sep 18, 2017 2:49 pm

Re: Distortion Generator potentiometers

Post by X100Ver10 » Thu Dec 21, 2017 1:15 am

Just an FYI - The Bourns slide potentiometers that I ordered will not work. The solder legs do not line up with the holes in the circuit board. Please disregard any Bourns part numbers that you may have seen in this thread.

The Alpha slide potentiometer does work great. The only difference is the black knob has a white line down the middle and the originals do not. The correct Alpha part number is RA2043F-20-10EB1-A100K.
Last edited by X100Ver10 on Wed Jan 24, 2018 3:11 am, edited 4 times in total.

RockmanCentralBob
Posts: 240
Joined: Fri Feb 06, 2015 2:10 am

Re: Distortion Generator potentiometers

Post by RockmanCentralBob » Thu Dec 21, 2017 12:57 pm

Have you tried calling Bourns directly?

One thing I've noticed about them is they change their part numbers over time for essentially the same part. So if you call them and give them a part number, or describe it's characteristics (size, shape, values) they can probably tell you what the current model of that part is and order it for you. I've done that before and they were most helpful.

X100Ver10
Posts: 83
Joined: Mon Sep 18, 2017 2:49 pm

Re: Distortion Generator potentiometers

Post by X100Ver10 » Thu Dec 21, 2017 9:34 pm

RockmanCentralBob wrote:Have you tried calling Bourns directly?

One thing I've noticed about them is they change their part numbers over time for essentially the same part. So if you call them and give them a part number, or describe it's characteristics (size, shape, values) they can probably tell you what the current model of that part is and order it for you. I've done that before and they were most helpful.
Thanks Bob for that suggestion. I will try that, if all else fails. I may have a line on the 3 smaller potentiometers in China. I am waiting on another response to my questions regarding measurements. It is looking better though and will keep this thread updated.

I did receive the larger potentiometers today that I ordered from Mouser. I think they are going to work. Except for the white line in the knob (LED?), everything matches up. Pictures attached.
IMG_20171221_151346.jpg
IMG_20171221_151322.jpg
IMG_20171221_151250.jpg
Bob, can you verify for me that the taper on the 2 larger potentiometers on the DG are A (logarithmic) and not B (linear)? I just want to make sure. I based my search for these from a post on the Gonna Hitch A Ride forum.
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RockmanCentralBob
Posts: 240
Joined: Fri Feb 06, 2015 2:10 am

Re: Distortion Generator potentiometers

Post by RockmanCentralBob » Fri Dec 22, 2017 1:16 am

No, they are B, Linear..... at least, that's what the schematic says.

X100Ver10
Posts: 83
Joined: Mon Sep 18, 2017 2:49 pm

Re: Distortion Generator potentiometers

Post by X100Ver10 » Fri Dec 22, 2017 2:58 am

RockmanCentralBob wrote:No, they are B, Linear..... at least, that's what the schematic says.
Just want to make sure we are on the same page. The 100K Volume and Treb Boost potentiometers on the DG are taper B (linear)? I was under the impression that taper A (logarithmic) potentiometers are usually used for Volume. Thanks. Sorry to be a pest.

X100Ver10
Posts: 83
Joined: Mon Sep 18, 2017 2:49 pm

Re: Distortion Generator potentiometers

Post by X100Ver10 » Sat Dec 23, 2017 2:34 am

Mouser has the B taper slide pots for the Treb Boost & Volume in stock too (Alpha part #RA2043F-20-10EB1-B100K). I ordered a couple of them. I'll measure the resistance of the old ones while sliding the knob and compare that to the new A or B taper pots to make sure I'm using the correct taper.

Also, I ordered several of the smaller B10K & B500K pots from China. If what is sent matches the pictures in the listing, we are golden for a source for those rare parts. Unfortunately, I have been burned before by the wrong picture of an item for sale (see my headphone amp gain knob thread). I'll update when I get them. It will probably be late January 2018 though.

I'm still working on the 2 switches for the DG. It doesn't look good.

RockmanCentralBob
Posts: 240
Joined: Fri Feb 06, 2015 2:10 am

Re: Distortion Generator potentiometers

Post by RockmanCentralBob » Sun Dec 24, 2017 7:22 pm

X100Ver10 wrote:
RockmanCentralBob wrote:No, they are B, Linear..... at least, that's what the schematic says.
Just want to make sure we are on the same page. The 100K Volume and Treb Boost potentiometers on the DG are taper B (linear)? I was under the impression that taper A (logarithmic) potentiometers are usually used for Volume. Thanks. Sorry to be a pest.
They are definitely B taper..... these are not for volume but for tone controls, so it makes sense that you would want an even taper. A log pot would make the change uneven at one end from the other.