Sovtek MIG-50 pots not working properly

[Bruce / Mission Amps]

I took the chasis out, I do not like how the pots are mounted.

Ha ha... if you decide to use discrete pots with solder lugs, (the correct fix for this) remember to solder wires onto the pots first. Mount them lugs up and reverse the wires from the pot's outside lugs, with respect to the board and where the other pots were soldered in.
You'll figure it out.

[corey]

I can't figure out the pot values by looking at them. Does someone know what the values are? Otherwise I will just find a schematic.

[rathmann]

http://www.freeinfosociety.com/elect...ovtekmig50.pdf

[Bruce / Mission Amps]

I just rebuilt another Sovtek today... a blown up Mig 60. The OT is shorted from the primary to ground off the center tap!! YIKES!
This one is not really very good sounding even after a replacement OT.
Very gainy with too much woofy bass, thick mids and not enough clear treble.
Oh well.... I guess I'm glad it's not mine.

[stormbringer]

removed post so that i don't hijack your thread...

[Trace]

A gentleman mentioned that the shafts were not standard and he is correct. If you want to use the typical Alpha pots you will likely need to drill the face plate/chassis but at the end of the day it's a good idea to replace the pots as they are known to fail. These amps were built from cheap parts (very cheap--lol).

All the best!
Trace

[trevorus]

The pots in the MIG are just like the ones in the Russian built Big Muff pedals. The knobs are also the same style. May help find some parts. I have one that needs pots changed eventually, but it will be a little bit. I put a Mullard Diamond Bottom 12ax7 in V1, and some old used Sylvania 6L6GC's, and it's sounding awesome. The MIG's are good amps, though they do have some weak spots.

[corey]

I assume this is the Alpha pot you are talking about? Or would I want the 250 VDC rating?

[corey]

I forgot to put the link in the post.

More Info for item R-VA-8MM-1L

[MojoGuitar]

This thread has the Mig 50 pot values: SovTek Mig 50 pot values & taper

[soundguruman]

The values are 3 X 1 Meg, 1X 250K, 2X 25K, BUT is better, comrades, to be putting a 50 K in place of the 25K MID control. This is giving the glorious Soviet amplifier more mid range adjustment.
I installed PEC stainless steel pots in the last one, but I just worked on a MIG 60, and the pots were much better, and mounted to the faceplate, so that one did not need the pots replaced.
In this amp, the ones with the plastic controls, and the 1/8" shaft knobs, should be upgraded to 1/4" shaft professional controls. The original ones, with the 1/8" shaft pots, don't last.



Anyhow, the stainless pots, which cost about $10 each, have a really nice adjustment range, much better than the usual pots that the factory installs.



You gotta install flying leads, from the board, to fit some professional grade pots in there. I glue mine down w/ epoxy, so although the pots are not permanent, the leads are.

[jmaf]

From soundguruman's photos, it looks like every other 24mm chassis mount cts/alpha pot out there?

CTS Audio Taper Pot 3/8" Bushing

[soundguruman]

The original pot was plastic, and the thread ended inside the amp. This leaves the 1/8" plastic shaft unsupported at the knob, leading to easy breakage.
The new pot is threaded all the way to the outside, has a 1/4" shaft. This makes it worthy of rock and roll, hard to break it!
And you might be surprised, the thing works perfect after you change the pots, it's like a new amp, like playing it for the first time.
It's a very clean loud amp, like a bassman or twin. Of course we could change that.





Potentiometer PEC Canada, Audio Taper, Carbon Element, Sealed Construction
Diameter (body of round control): 1.115" OR 28.35 MM
Bushing (Threaded) Length: .444" OR 11.29MM
Bushing (Threaded) Diameter: .365" OR 9.28MM (approx. 3/8 inch hole)
Shaft Length: .315" OR 8MM
Shaft Diameter: .248" (1/4" approx.) OR 6.32MM
Total Reach (through hole, shaft + bushing) Length: .745" OR 18.93MM. Max length- from the body of the pot to the end of the shaft.
Hardware provided: 1 lock washer + nut
Knob Required: for a stainless steel shaft, you will need knobs with a steel insert and setscrew. A brass setscrew does not work on the PEC potentiometer.

You will need to shim / change the height of the mounting bar to accommodate the larger (professional grade) pots. You will need to adjust the height of the circuit board insulators. You will need to drill out the bar and faceplate to 3/8" to install the new controls, you will need 6 extra nuts to secure the pots on the outside of the faceplate.