Problem with the "envelope pot" Moog MF101

I’ve just received a second hand Moog MF101.
Everything work well excepted the envelope follower. I mean, when i turn the “envelope amount” pot nothing happen!! when i turn the pot at half, the sound is cut.I think this pot must transform the MF101 into an autowha pedal but in my case this pot just cut the sound!!!
I 've tried to modulate the envelope with an expression pedal but it’s the same story.
I need help… or advice. I can’t find any service manual for the MF101 and i really want resolving the problem.
Is it a possible “dead” potentiometer? in that case how to change the pot and what’s the good value?
PS: excuse my bad english i hope you’ll understand
Thanx
Julien

Run a strong signal with lot’s of dynamics into the Fooger. Observe the ENV lamp as you adjust the pot.
The pot is just an attenuator for the envelope follower. It doesn’t ‘create’ an anvelope.

I’ve tried with a drummachine (Soundmaster St305) at high level output! On the MF101 i can see the envelope lamp flashing red more faster if i turn the pot but if i turn the envelope amount pot at 1/3 it cut all the sound comming from the drummachine. I suspect the pot is “dead” it’s also noisy and scratchy when in use!!!
Do you think it’s a good idea to change the pot? What’s the exact value and where to find a new one?
Thanx

Run an instrument into the Audio Input
Turn the resonance to self-oscillation at a low Cutoff
Mix to 10
Set Amount to zero
Send the Env Out CV through a patch cord to Cutoff In

The overall amount is fixed but you should hear the filter being modulated.