Sunn Beta Lead potentiometer question

[sonichris]

I have a beta lead with a broken treble pot (the knob broke off). I checked the schematic and it seems to be a 1 meg pot, no info on whether it's a linear or log sweep so I'm assuming it's linear? Having a hard time finding a replacement, anyone know of a supplier? It's a 4 leg pot, 4th leg is just for support on the board. I have read that these have been replaced with a 3 terminal pot wired to the board when an exact replacement couldn't be found but would prefer to replace with original style.

[glebert]

Picture would probably help. For linear vs taper use a screwdriver or knife to turn the broken shaft into the center-ish position and measure resistance to the wiper leg and that should tell you. If you can't find the right part you might be able to swap the shaft and wafer from a different one into the original case.

[sonichris]

Thanks for the info. The pot is still soldered to the board so I couldn't get an accurate reading, however I was able to find a complete schematic that shows it being a 100k linear pot. Now I just have to find that style. Saw a video on youtube where someone just took the pot apart and replaced just the plastic shaft, so now I'd be happy with any working or non-working pot of any resistance, just that same style. I will upload a picture tonight when i get home.

[sonichris]

found a picture online. this person modified a 3-terminal pot by swapping the original legs over. bottom right picture is original. the shaft is white plastic and is a "D" shaft, it is round with a flat on one side.

[DrGonz78]

Perhaps the peavey pots will work?

https://www.tubesandmore.com/product...y-audio-spider

[sonichris]

Hmmm... Shaft is different and that 4th leg would have to be moved to the right. It's strange that so many of these amps were made and no one makes these.

[The Dude]

I would try this.

https://www.mouser.com/ProductDetail...50T328F104A1A1

You'd just have to extend the pot legs to the proper length. You could cut the legs off the old pot and use them to extend the new one. The only problem might be that the D shaft may be positioned differently than yours and the knob pointer may end up being off. I have no idea without both parts in front of me.

Edit: I just noticed they are not in stock, but you can probably find them or similar elsewhere.

Edit (again): Digikey has them here.

https://www.digikey.com/en/products/...xLgEFdiQBdAXyA

[sonichris]

Thank you, I might have to end up going this route. Also thanks for reminding me about where the flat lines up, wasn't thinking about that.

[J M Fahey]

I was able to find a complete schematic

So post it here, how can we help you otherwise?

Pictures too, same thing.

[sonichris]

I repaired the potentiometer, here is the repair thread.