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10M RA & 4M RA pots needed


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9/3/2000 11:37 PM
nuke
 10M RA & 4M RA pots needed
I'm looking for a 4-megohm and a 10-megohm reverse-audio taper pot for a blonde-fender restoration project.  
 
anyone have a source new or used for either, especially the 10 meg? I can probably sub a 3 meg RA for the 4, but the 10 meg is hard to come by.
  
9/5/2000 3:58 AM
MBSetzer
Hi Dr. N:  
 
Not too long ago here or in a stompbox area someone described how they disassembled a pot and sanded the carbon evenly until the element increased resistance to where they wanted it.  
 
This might help but it does sound fairly desperate, sure would be nice to get regular new parts that don't need modification to do the job.  
 
Mike
  
9/5/2000 8:46 PM
PTJohn
Yeah, that was me. I turned a 50k linear pot into a crybaby pot by shaping the resistor element. Works very well with low power levels. Not too difficult to do, but if you need something that dissapates wattage, it may not work too well. If you tried to turn a 1M into a 10M, you'd be shaving a lot of carbon off. You might be better off using a multiposition rotary switch with resistor dividers and experiment to get the right drops for your tone. The other solution would be to put in a CLM650 or NSL32AA optoisolator that runs from 400 ohms to 10M and run a divider circuit tacked to the back of the pot.  
No other suggestions here, other than buying salvaged test gear and ripping it apart in the hopes of finding the right pots.  
 
Good Luck.  
PTJ.
  
9/6/2000 8:23 PM
nuke
How did shaving the pot work out in the long run? Since this will be an intensity control in the vibrato circuit, it will be a front panel part so it needs to stand up to use.  
 
I'm considering shaving a 3M RA, since that's all I can get. As long as I can get it in the ball park it should work.  
 
I'd be happy if I could track down a used 10M RA somewhere. There's nothing quite like the blonde vibrato (in the higher line amps).
  

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