Another method honed to perfection. Better than mine, when a hole punch is cheaper to acquire than a 3D printer

A layer of the rubber foam on the bottom of the coffin would solve the problem with light intrusion.
-Helmut

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.

 Hello Aquataur,
               Well impressive work and effort on your part, keep it up.
I just read some of you web page,, wow you have obviously done a lot of research.

In regard to the 3 issues of using heat shrink tube,
I agree as my first few attempts were a failure.

So now having constructed a few of Mictester's simple compressor (RCC) circuits I've refined a simple solution. So for those that don't have a 3D printer this is my DIY Vactrol setup which has worked well for me.

Achieved by simply punching out 10mm round plugs of high density black foam rubber as a base holder for each side. This overcomes the fiddly problem of assembly. wise to test that both the Leds and the Photo resistor are working before you heat shrink it.
The tube is also 10mm which makes a nice press fit even before heating. Cut the tube a bit longer than the 2 parts. (Pics below) The tube in pic is a bit short, used just for refference.
The lip at the base of Leds will need to be filed flat so the 2 leds sit in paralell, makes for a better fit in the tube.

2 things worth note;
I believe photo resistors work best with Green Leds, something to do with the different wavelength of colours,, better minds may know details on that. I use semi clear green Leds.
And make darn sure the leds are wired back to back. don't ask how I know that,,, lol.
Phil.

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

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

You cannot view this attachment.

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 

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

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.

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.

You cannot view this attachment.

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 

You cannot view this attachment.

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

You cannot view this attachment.

And no I won't be attempting that 

Now my volume pot is almost liberated

You cannot view this attachment.

I need to find a suitable replacement it's A250K

Also would you clip it off or desolder 

Yes sir thanks 

I think I lucked out getting the black one 

Black one MPA-200
-"normal" output 
-Stereo output so I can possibly use it to listen to ball games etc (loudly  )
-to my noob eyes looks evenly divided two channels each the same 
Kinda like working on drum brakes...don't take both sides apart at the same time

Silver one MPA-100
-weird multi voltage speaker output   
-Output transformer ?!   

So I'm hella glad to have the MPA-200

I need to order a volume pot just replacing that should take me about six months 

Not to bust the subject of this thread, but a warning ahead. 3D printing is a can of worms. As with everything, I advise to look into this subject only if you are determined to spend a lot of time with the subject. Don't be betrayed by the simplicity of a printed thing. An immense amount of work and knowledge goes into some designs, so that the print comes out smooth, functional and appealing.

Go to somebody who is in the know armed with a ready made .STL file such as the one I uploaded, buy the guy a coffee and wait for the print to complete. That's the way to go.

Look at the knobs a guy makes who does professional printing for the matter. Knobs are not only a functional element, but also your haptic and visual interface to a device. That said, his knobs are meant to go to cooking places and thus are just functional. Better a not-so-perfect knob than none.
3D printing has advanced incredibly in a short time, but for strength and surface cosmetics, a conventionally manufactured knob is unsurpassed.

A functional thing as the housing for a vactrol has no claim for a perfect look neither for durability.