Volume/power pot for a multivox keyboard

[Josemitejam]

Hi all,

The volume/power potentiometer is very crackly and will complete cut the volume at different points in its rotation. It will fully click the power on and off though. So I'm looking at getting a new pot for it, here's some pictures below. Can someone guide me to the correct potentiometer to buy? I see lots of options online and I'll surely buy the wrong one on my own!

Thanks a ton!

Joe

[MikeA]

What you have looks like an ALPS (Alpine) dual gang, 50k ohm, audio (log) taper, solder lug pot, 24mm diameter, with an SPST on/off switch (the TV-1 layer at the bottom.)  All that should give you the criteria you need to make a choice.  For example, this one is a match except for the on/off switch, which you'd have to wire out to a separate toggle but there may be a closer match out there somewhere: 
https://www.tubesandmore.com/products/potentiometer-alpha-audio-dual
https://smallbear-electronics.mybigcommerce.com/alpha-dual-gang-24mm-linear-audio-taper-solder-terms/
(same pot, two different sources)

[Kevin Mitchell]

Hmmm. Dual gang 24mm 50KA with SPST switch that actuates when fully counter-clock-wise (apposed to a push-pull switch).
Is that 3/8" bushing?

Searching....

Edit. Aww Mike beat me to the details....

[MikeA]

Kevin, I don't hold out much hope for the switch part, as you say, they've all gone to push-pull to serve the guitar market, rather than the "turn-to-click + volume" audio market of yore.

[Kevin Mitchell]

Kevin, I don't hold out much hope for the switch part, as you say, they've all gone to push-pull to serve the guitar market, rather than the "turn-to-click + volume" audio market of yore.

Yeah, I was being optimistic 

I just looked at the entire Alpha catalog. They do not carry anything appropriate for this.

If you can't find an old-stock replacement you could get creative and use an optocoupler like VTL5C3-2 (or roll a pair yourself) to emulate a dual gang taper. This way you can use a single gang switching potentiometer with wiggle room for the needed value.
It is just a level pot after all.

Edit; it's also worth while to shoot some cleaner in there. Perhaps there's gunk covering the carbon track and the rake is skimming over it. Worse case is the track is already gone.

[Josemitejam]

Thanks everyone! I just ordered some cleaner, hopefully that will do, if not I'll be taking up the other suggestions!

Thanks!

Joe

[anotherjim]

All kinds of pot assemblies still exist, just some are not considered a jellybean item anymore - a batch needs to be commissioned.
https://www.robot-italy.com/it/panel-mount-10k-dual-log-potentiometer-w-on-off-switch-10k-dual-log-w-switch.html
You need a 50k audio taper dual-gang with a rotary power switch. I found a 10k. This might work if you know the circuit, it may only need larger coupling caps to feed the lower resistance.

[aron]

I don't remember that keyboard but it brings back string ensemble vibes!

[anotherjim]

It's an electronic piano. I don't recall it either. The only electronic ones that are well remembered were the RMI and Farfisa models, and mostly for the non-grand piano sounds that they could do. I can't find a free schematic
https://www.synthmania.com/multivox_mx-20.htm