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I'm attempting to replace potentiometers in an old guitar combo amp. Here's how they look:

a potentiometer

Besides the usual three contacts, each pot has a mounting bracket with four more pins. They look and feel very robust, in fact, the board is affixed to the chassis only with these potentiometers, the rest of it hangs in the air. I've never seen such pots before (but I'm a hobbyist), is it a common design? Does it have a name? Can I buy replacement parts? If not, how would you approach this repair?

While we are at it, on the schematics the pots are labeled "100K1" and "100K3", what do "1" and "3" mean? Thanks!

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    \$\begingroup\$ I would assume the 1 and 3 are the number part of the reference designator, and 100k is like the "R" part. If you can't find a pot with legs like this you could just use another method to support the board, like some screws and sheet metal bent into a bracket. \$\endgroup\$ Commented Mar 12 at 20:39
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    \$\begingroup\$ google.com/search?q=potentiometer+with+bracket&sclient=img and then hit the "Images" button. \$\endgroup\$ Commented Mar 12 at 22:45

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It looks possibly like a custom made part. I've never seen one like it in any manufacturers catalogue. The 4 pins on the bracket are for mechanically attaching the assembly to the board, and perform no electrical function other than possibly earth screening.
I would suggest you try the following steps.

  1. Carefully remove the pot and it's bracket from the board. It's impossible to tell from the photograph if the bracket is soldered or crimped somehow.
  2. Once free you can measure it to check you have correctly identified it's value and obtain a similarly sized, modern replacement pot.
  3. Now remove the old pot from the bracket (you may have to damage it) and assess the situation. With a bit of luck you can drill a hole through the centre of the bracket to mount the new pot so that the shaft sits at the same height above the board, but but facing the other way. The body of the new pot sits where the old one did, but the shaft points the other way.
  4. You can now reverse the bracket so the flat side faces out and the shaft points in the correct direction again.
  5. Then it's just a matter of reattaching the bracket to the board using the original method and adding 3 wires from the board up to the terminals of the new pot.

From a comment to the OP question by Transistor it appears that this assembly was a catalogue part, but is now classified as vintage (read obsolete). I can't identify a current source of supply.

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