maestro mps-2 advice?

[pinkjimiphoton]

hi guys,
i picked one of these up a while ago with the intention of fixing it and adding to my collection,  but the car whacked a pothole the other nite and i gotta come up with enough for the repair. <not cheap> so i wanna get it going and throw it up on the bay with some other crap.

anyways,... is there any advice to getting these suckers to phase? it passes signal, i can see modulation happening on my meter, the fets seem to be working,  but i can't get it to do anything ... my billion dollar question is...

could it be the freakin pot? seems like i lose signal there. i'll try n get voltages, but was curious if i should add trimmers to it or something and change the fets to something like a 5457 or j113 <which i DO have bags of>

any help appreciated. its been bugging me for months now. just haven't had a chance to get back to it, and... like i said, i'm about 1200 short of the 1400 i need to fix my car

[Mark Hammer]

Based on your description:

• it "passes signal"
• you get measurements indicating a functioning LFO

Note that the "bypass" is essentially a mechanical version of how many pedals electronically produce bypass/engage.  That is, instead of using a JFET to block/enable the wet signal, a switch is used to either connect the wet path up to a passive mixing node...or not.  So, even if you had flawless modulation, if the footswitch - which is older than the majority of members here - was not making good reliable contact, you would get "signal passing" in both bypass and engage mode but not any audible phasing in effect mode.

It's an easy test to carry out.  Just bridge the footswitch and see if that restores the effect.  If not, then the next culprit in line would be a bad 741.  The test for that is also easy: stick your probe at pin 6 of each of those 741s and see if you get signal at its output. 

Given the two things it does do, my money is on one of those two issues.  Yes, there could be an issue with one of the 2N4303 JFETs, but the odds of all of them crapping out are very low, in which case you'd still get some audible phasing, just not as strong.  So it's gotta be something creating a blockage of the wet signal.  It could be the 150nf cap before the footswitch, but I doubt it.  Still, put that the third item on the list.