Realistic MPA-200 volume pot replacement

[saturated]

Ok guys time to get to work 

First order of business attempt to reach this little guy

Oops need some background info: customer (me) claims left channel spins 360.  Amp has been tested seems to pass DBT and passes sound from guitar 🎸 (not the plan just testing)

So I figured the best way was to disconnect the front face plate.  That did not leave me much room because the wires are tightly bundled and I do NOT want to open that Pandora's box unless I have to.  So I laid it upside down and access was better.

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Then I saw I could unscrew the potentiometer bracket so I went at it with a sideways screwdriver but that was tedious I remembered a little ratchet set I bought a while back 

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This has been educational because I learned there is a song by Eric Johnson called "zap"

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And no I won't be attempting that 

Now my volume pot is almost liberated

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I need to find a suitable replacement it's A250K

Also would you clip it off or desolder 

[g1]

From you pics in the other thread it looks like it's an Alpha brand A50K (log) pot.
First before you even disconnect it I would pop the back cover off it and check if maybe it has just come apart.  If the plastic piece with the wiper and stop has popped off the shaft you may be able to just press it on again.
Otherwise, if you have to replace it, Alpha pots are easy to come by, but you will want to match up the shaft so the know will fit right.

[g1]

Maybe this:  https://www.ebay.ca/itm/304482856805

[saturated]

Yes sir thanks

I might be up the creek trying to find a pot with the splined split  long shaft.  I think I looked at every one on eBay and Mouser last night 

None are even close to this length I need to measure it

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I know

I still need to attempt the repair

I guess I'm getting a taste of what the big boys have to deal with when doing this professionally 

"Hey man I fixed your amp.  If you need to adjust the left channel volume just use a little flat head screwdriver 🪛"

 

But I'm really excited about this amp 

[saturated]

One thing I need to learn about is what happens if a different value k ohm potentiometer is substituted 

If I need a 50k ohm

-what happens if I put a 10k ohm in

-What happens if I put a 100k ohm  in

[g1]

What happens with different values depends on the circuit.  It can affect the loading on the previous stage, change the knob settings, or make even bigger differences if it is in the feedback loop of an op-amp.

Sometimes what is done is rebuild with parts from a similar pot that is the correct value.  You might be able to swap in the 'wafer' from an Alpha pot that has the correct value but the wrong shaft.

[Tassieviking]

What is the length of the shaft ?
You will want to measure the splined shaft and the threaded shaft length and also add them together to be able to find a replacement.
The other option is replace both pots and also the knobs and you get a lot more choice to finding the pots, you can look at solid shaft pots or D shaft pots if you replace the knobs as well.
What is the diameter of the knobs ?

[galaxiex]

You can get "universal" solid shaft pots that have a long "cut to length" shaft.
Requires new set screw type knobs.