Mechanical fix for a switched potentiometer?

[Harry Klippton]

My guitar teacher has this vintage gretsch 6152. The tremolo speed control is a switched potentiometer where it clicks off the tremolo circuit when you turn the knob all the way counter clockwise (like the on/ off of a tweed champ?). At some point, the shaft came loose and slipped down inside the chassis. The nut part of the threaded sleeve fits in the tabs on the base of the pot, but it doesn't stay put. Is there a fix for this? The pot is 500k and the only switched pots I can find are 1M for champs. Looking for experienced advice on this

 

[Bricksnbeatles]

there might be a way to fix that, but from the picture it appears to be straight-up structurally broken.
I did find this though— just gotta cut the shaft down to the correct height:

Home

500K Audio Taper Potentiometer with Switch 1/4" ShaftAudio taper 1/4 watt monaural potentiometer with M8 x 6.5 mm L bushing. Built-in switch turns power source on and off with volume control.Specifications: • Shaft height without threads: 0.9" • Total height including body and switch: 2.18" •...

www.parts-express.com

 

[Harry Klippton]

Oh yeah I forgot about the long shaft ones. I might have to consider that too

 

[giovanni]

Worst case scenario, could you add a separate switch? Or look into a push pull pot?

 

[Feral Feline]

Same sort of thing happened to my Trend's tremolo pot, and the Vol turned out to have a problem as well, so I ordered a couple of B500k switching pots. I thought I got the pots from Amplified Parts, but they're not on the invoice so I don't know where they came from. Amplified parts does have a switched A500k pot (same as what Bricksnbeatle found for you).

It's been a while since I tinkered with my amp, and it's still sitting at my friend's atelier since I don't have a step-down transformer at home, but I'm sure we wound up installing a 1M pot on the volume instead of the stock 500k the amp came with. If that's the case, I should have a spare split-shaft B500k switching pot kicking around.

I'll be going back on Tuesday to work on my 5E3, so I'll have lookeeloo for the B500k-switched and be able to tell you then.

 

[Stickman393]

Are you sure that you're installing that threaded sleeve correctly?

You said that the nut fits in the tabs on the pot...I don't see how that could possibly hold that part in place. From a glance, It looks like you need to flip the piece In your hand upside down: the threads look like they're supposed to be inserted in the void *around* the shaft of the potentometer. That is, there should be a mating threaded section that you could screw the threads in to inside the pot, with the faceplate sandwiched between the piece in your hand and the potentiometer.

If those threads are stripped, you may be able to salvage it with a little soft metal...sometimes I'll wrap a little bit of copper from wires around stripped threads before I re-insert. That works sometimes.

A quick search on ebay for a 500k switched potentiometer yeilded at least one result with a knurled short shaft, if keeping it looking original is important. There are also other options available such as push-pull or push-push pots that you could adapt to this purpose.

 

[Harry Klippton]

Got this all worked out. I disassembled the pot, took the top plate off and super glued the threaded shaft in, that way no glue could get down in the guts.

There was a lot of extra lubricant or contact cleaner when I disassembled the pot and I'm thinking that might have made the press fit slip out. Now I'm off to make a footswitch for the reverb and tremolo circuits

 

[Stickman393]

Good to hear that you got a fix in place!

Still, even looking at it assembled: I'm *highly* skeptical that those tabs were meant to hold the hex part of that piece in place.

You notice how the other parts of the potentiometer use folded tabs OVER adjacent surfaces in order to keep everything together? You would need something similar in place over those two tabs: a friction fit between two soft pieces of metal like that essentially has no structural integrity. It seems to me that the slightest lateral force would knock it loose, if that was the original intention.

That said; I could be wrong. I am curious to see how the other potentiometers mount to the faceplate there if you're up for some exploration, but that's up to you.

Cheers!

 

[Harry Klippton]

Good to hear that you got a fix in place!

Still, even looking at it assembled: I'm *highly* skeptical that those tabs were meant to hold the hex part of that piece in place.

You notice how the other parts of the potentiometer use folded tabs OVER adjacent surfaces in order to keep everything together? You would need something similar in place over those two tabs: a friction fit between two soft pieces of metal like that essentially has no structural integrity. It seems to me that the slightest lateral force would knock it loose, if that was the original intention.

That said; I could be wrong. I am curious to see how the other potentiometers mount to the faceplate there if you're up for some exploration, but that's up to you.

Cheers!

I pulled the reverb pot, which is the same, to check before doing this. The four fold-over tabs don't hold the threaded shaft in place, just the two raised edges keep the nut from spinning