Regulating Vintage MXR M117

Hi!

I got a 1979 MXR M117 flanger that need to be regulated, it's oscilating with the regen all the way up...
Contacted MXR tech for some tips about that, since is not in a current production, and it's old and awesome  , but the guys told me to F"#$ myself... so I need help on this...
Anyone? Any service manual around? I got the schematics.
Thanks in advance!
Cheers

Ed

Maybe you can get lucky if you contact someone at ART... Some guys that started there were from early MXR I believe.

What is it you are trying to do? It's a bit vague to me what you are describing.....

I don’t have a service manual but regen will make feed back when all the way up.  The caps in it are pretty old . .  Check them or just replace them.

fazer said:

I don’t have a service manual but regen will make feed back when all the way up.  The caps in it are pretty old . .  Check them or just replace them.

Click to expand...

Does it only happen when the pot is all the way up? If so, its probably just the feedback of the effect. If you dont like it then put a resistor in series with the top of the pot. Choose a value less than that required to feedback too much.

Some people like it when a delay can go to greater than 100% feedback. If it troubles you, don't turn the knob that far?

SaMpLeGoD said:

Hi!

I got a 1979 MXR M117 flanger that need to be regulated, it's oscilating with the regen all the way up...
Contacted MXR tech for some tips about that, since is not in a current production, and it's old and awesome  , but the guys told me to F"#$ myself... so I need help on this...
Anyone? Any service manual around? I got the schematics.
Thanks in advance!
Cheers

Ed

Click to expand...

That is not something I would expect to change over time, but should be simple enough to reduce the recirculation signal.

Identify the regen pot and look at what is connected to it's wiper, generally a resistor. Making that resistor a larger value will reduce the amount being recirculated. There may even be a trimpot in that path, if the design targeted for being on the edge of runaway.

Do not start randomly turning trimpots without first being certain of their function.

JR