(Yet Another) Electric Mistress Help Request

[boyersdad]

Hey all,

I have what appears to be a 1978 V2 Electric Mistress flanger. It was in rough shape when it was given to me, as it didn't work at all. The enclosure was rusty and in insides were dirty and in a mess.
I've given it a good clean, and mostly got it working. The problem I'm left with is that there is still an unacceptable amount of "swooshing" at output, even with the input disconnected.

This is the schematic that most closely resembles my board: http://www.metzgerralf.de/elekt/stomp/mistress/images/1976-electric-mistress-v2-schematic.gif

Someone (maybe factory?) has modded the PSU in this guy to use an 78L12 12V regulator instead of the 741 (which is present and still operational on the board). Two transistors have been cut off the board (one would have been the original transistor in the PSU circuit, but not sure what the other one was...). Either way, power supply seems stable. I'm getting correct voltage where I need them. The other difference is that the Q labled BC177 is actually a BC309.

I replaced all the electrolytic caps with new ones of the same value (except 33uf replaced with 47uf, and 2.2uf replaced with 2x4.7 in parallel).

I'm powering the unit via 18.0V from a lab grade bench power supply. It's CLEAN.

I did the scope and function generator alignment process described here: http://www.metzgerralf.de/elekt/stomp/mistress/align.shtml#2

I replaced the trimpot for the feedback, as it seemed a little out of sorts.

There were several red painted resistors that "looked" really bad as the paint was bubbled and flaking, however they measured in spec. I replaced all of them just to be safe.

I'm basically left where I feel everything "should" be working correctly, yet still sounds dirty and with too much swoosh and wine at output.

Any suggestions would be great! Thanks all!

[pappasmurfsharem]

(except 33uf replaced with 47uf, and 2.2uf replaced with 2x4.7 in parallel).

2 x 4.7 in parallel is 9.4uF it works opposite for capacitors vs resitors

You need to run them in series to get 2.35uF

I don't know if that is your problem however.

[boyersdad]

Whoops, quite right. They are actually in series, not in parallel. Good catch.

[boyersdad]

This noise that I'm experiencing is quite common to SAD1024 devices. I have an original Memory Man which is also basically unusable due to the extreme noise bleed.
I'm wondering if maybe the clock noise and/or LFO are bleeding into the audio by pulling on the PS... Perhaps I should try bumping the supply filtering way up. I'm just going out on a limb with this one, but I'm really running out of ideas here.