Bypassing broken gain pots - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th May 2008, 12:47 AM   #1
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
Default Bypassing broken gain pots

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?
  Reply With Quote
Old 17th May 2008, 02:25 AM   #2
diyAudio Member
 
gtforme00's Avatar
 
Join Date: Oct 2004
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
  Reply With Quote
Old 17th May 2008, 03:45 AM   #3
diyAudio Member
 
Join Date: Mar 2007
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.
Attached Images
File Type: jpg pot.jpg (19.1 KB, 178 views)
__________________
If it ain't broke Don't fix it
  Reply With Quote
Old 17th May 2008, 03:54 AM   #4
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Do you know what value it is? Does it look like these.....

Click the image to open in full size.
  Reply With Quote
Old 17th May 2008, 04:30 AM   #5
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
Quote:
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

Click the image to open in full size.
  Reply With Quote
Old 17th May 2008, 04:36 AM   #6
diyAudio Member
 
Jonny Hotnuts's Avatar
 
Join Date: Dec 2007
another pic

Click the image to open in full size.
  Reply With Quote
Old 17th May 2008, 04:54 AM   #7
diyAudio Member
 
Join Date: Mar 2007
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.
__________________
If it ain't broke Don't fix it
  Reply With Quote
Old 17th May 2008, 05:21 AM   #8
diyAudio Member
 
gtforme00's Avatar
 
Join Date: Oct 2004
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.
  Reply With Quote
Old 17th May 2008, 06:00 AM   #9
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Quote:
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.
  Reply With Quote
Old 17th May 2008, 04:05 PM   #10
diyAudio Member
 
Join Date: Feb 2008
Send a message via AIM to MatthewS Send a message via MSN to MatthewS Send a message via Yahoo to 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
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Gain Blockwith Variable Loop Gain Bonsai Solid State 17 11th July 2008 03:40 PM
Bypassing B+ in PP amp oshifis Tubes / Valves 6 5th May 2008 09:28 PM
Heretical Unity Gain line stage PLUS a little gain ? yagas Tubes / Valves 7 24th January 2006 02:30 PM
Alps pots vs. TKD pots? TKD worth the extra$$? G Tubes / Valves 11 17th August 2004 05:33 AM
Why bypassing this way? StefanJ83 Parts 4 30th January 2002 11:38 PM


New To Site? Need Help?

All times are GMT. The time now is 01:34 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2