Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: vidmachine on May 22, 2019, 11:36:44 AM

Title: Another Randall RG100ES question
Post by: vidmachine on May 22, 2019, 11:36:44 AM
Can any one help me identify and locate a replacement for this (see photo.)  It is the mid pot for an RG100 and is believed to be a 2K Linear pot.  There are numbers but I can't seem to find a match.  seems to be a 3/8" bushing and 1/4" shaft.

It has a problem with crackle and the contact cleaner didn't help.  It also has a very small spot where the sound volume jumps up right around 10 o'clock.
Title: Re: Another Randall RG100ES question
Post by: galaxiex on May 22, 2019, 06:16:54 PM
Looks like a CTS pot.

The number 137 is the EIA code for CTS.

The next 8929 is the date code. Probably 1989, 29th week.

The other numbers spec the pot.

Unsolder the pot and ohms measure from outside lug to outside lug to find the overall resistance.

Turn the shaft to center and measure ohms from middle lug to each outside lug.

Compare and if approx the same, it's a linear pot.

If one outside lug reads much higher (or lower) than the other, it's likely a log pot.

Got to DigiKey, Mouser, etc to find an equivalent.

DigiKey has the 450 Series of "Stock pots" that can be ordered/configured how you like.

Look in this pdf...


Title: Re: Another Randall RG100ES question
Post by: vidmachine on May 22, 2019, 11:17:47 PM
Thanks. I pulled it out and dissected it.  There was literally no carbon left on the track.  I’ll get a replacement and see what happens.   
Title: Re: Another Randall RG100ES question
Post by: edvard on May 27, 2019, 03:24:05 PM
Schematic says it's a 2K linear.


EDIT: Ooops... 5 days too late... Have you fixed it yet?
Title: Re: Another Randall RG100ES question
Post by: vidmachine on May 29, 2019, 12:30:51 AM
Pot is in but I had to use a smaller diameter shaft.  It functions fine.  Still need a good loud test to see if it is going to solve all my concerns.