1979 Super Reverb Push Pull Pot Master Volume Replacement

[bobloblaws]

So this amp is one of the dreaded ultra linear models. The push pull volume pot was damaged in transit. As far as I can tell the only replacement available is the one advertised here https://www.amprepairparts.com/fende...tm#ctsswitched , it's the Revisit brand pot, part # P-V1MA-MV. So I ordered the pot but that turned out to be a bust. First of all, the thing did not clear the bottom of the chassis when trying to mount it in its place on the front panel. So I pulled out my Dremel tool and shaved a bunch of material off of the plastic housing to get it to fit. Then I encountered another problem. The shaft did not turn freely, it was very stiff. I ended up ruining a couple of brand new replacement knobs trying to tighten down the set screws enough so that the knob would turn the shaft without slipping. The threads in these cheap plastic knobs get stripped very easily. So then I disassembled the damn thing to try and figure out why the shaft was so stiff and to see if I could get it to loosen up somehow. But that was to no avail and ultimately it just ended up wrecked, filed under "G".

Soooooo, does anyone know of another source for these pot/switches? Or have some idea how I could McGuyver it with a similar product? Also, the knobs I have I got from Antique Electronic Supply/Tubes And More. Does anyone know where I could find replacement Fender knobs of a better quality?

Fender-Super-Reverb-Ultralinear-1978-1981-Schematic.pdf

[Bloomfield]

Lots of places have push-pull 250K and 500K for guitars. Perhaps you could swap out the wafer with the resistance track from another pot of the same brand, although I have never tried it. Nextgen near Ottawa have CTS and Alpha both with knurled shafts, but you might be able to make something work.

nextgenguitars.ca/categories/potentiometers.html

Andy

[nevetslab]

You might try this Alpha 1M Audio, DPDT Push-Pull switch from Antique Electronics Supply https://www.tubesandmore.com/product...ng-dpdt-switch

The bushing is 7mm dia, 7mm long, but you should be able to retofit it into the amp. I'm assuming it is the same panel mounting as the SF 135W Twin Reverb, mounting nut NOT locking down the escutcheon panel. I've bought both the original Fender knobs as well as their look-alikes from Antique, and have had good luck with both. Darren Riley carries them as well for more $$

[bobloblaws]

You might try this Alpha 1M Audio, DPDT Push-Pull switch from Antique Electronics Supply https://www.tubesandmore.com/product...ng-dpdt-switch

The bushing is 7mm dia, 7mm long, but you should be able to retofit it into the amp. I'm assuming it is the same panel mounting as the SF 135W Twin Reverb, mounting nut NOT locking down the escutcheon panel.

Cool, I think that one will work. I don't know what you mean by this though "...mounting nut NOT locking down the escutcheon panel".

[Tom Phillips]

May I also suggest that you consider removing the push/pull switch from the circuit? If the user likes the sound of the distortion when the knob is pulled I would understand why you would want to keep it stock. However, I have never found anyone who liked the distortion produced by that particular Fender circuit. I can add more info it you are interested in this suggestion.
Cheers,
Tom

[bobloblaws]

May I also suggest that you consider removing the push/pull switch from the circuit? If the user likes the sound of the distortion when the knob is pulled I would understand why you would want to keep it stock. However, I have never found anyone who liked the distortion produced by that particular Fender circuit. I can add more info it you are interested in this suggestion.
Cheers,
Tom

I'd like to be able to do that but this amp will be for sale in my friend's guitar shop so it really should be kept stock I think. Or maybe not.

[nevetslab]

Cool, I think that one will work. I don't know what you mean by this though "...mounting nut NOT locking down the escutcheon panel".

The escutcheon on the Fender SF 135W Twin has a large dia hole thru it, so the mounting washer/nut wasn't clamping the escutcheon down (effective panel thickness is chassis + escutcheon in that case). Here, you're just dealing with the 3/8" dia chassis hole. 7mm dia bushing on this replacement pot is smaller...0.276" dia. You may need a shoulder washer to center it, for one. The original pot's bushing is longer than 1/4"..enough so I was recently able to use a larger washer to clamp down the escutcheon, where it had been bent out of whack after the rear adhesive had failed, so it aided in holding it all down. If the escutcheon (silver labeled panel over the chassis front panel) is still in shape, not bending out at the ends, then you shouldn't have any issues, other than dealing with the larger mounting hole/hardware issue that imposes.