Home Forums Help/Technical Questions HELP! Vintage electric mistress makes sound but no effect.

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  • #83079

    Hi all, I had posted on this forum back in 2010 about my electric mistress, the original post can be found here for some background information to my problem.

    https://www.ehx.com/forums/viewthread/4029/#29052

    Back then I had given up on fixing my pedal.
    Well a few years and some better electronics repair experience later I have decided to give this pedal a go again.
    After a lot of researching and comparing schematics and pictures, I have come to the conclusion that I have a modded EH5150D. The closest match to my pedal I have found is this.
    http://www.metzgerralf.de/elekt/stomp/mistress/deluxe-electric-mistress-v3.shtml
    However there are some minor differences to note.

    My pedal is in a silver case with black print, not a green and black print.
    My board only has 3 trim pots as shown in the last pic on that page, not 4 as seen in the 4th pic on that page.
    My pedal has a small disc capacitor on the back of the board marked RMC N150
    My pedal does not have an onboard transformer but instead has a 1/8″ jack to supply power. the screw holes for the transformer are there which leaves me to believe that this was modded before i got it to remove the transformer and add the 1/8″ jack.

    Now after comparing a lot of different pictures of DEM’s and various schematics I have concluded that this unit in fact takes 24v AC not DC. Hoping this was the root of my original problem all along I had decided to reconnect all wires according to the pictures and try an 18v AC 800mA power supply with the pedal. And now I have a bit of progress.

    When powered the pedal now gives me my guitar sound when both on bypass and activated.
    When activated I can still hear a faint ticking noise that speeds up or down when the “rate” knob is adjusted.
    The “depth” knob has no effect.
    The “color” knob now actually does something! (progress?) when i adjust the color knob it basically acts as the tone control on my guitar would. when turned down it kills all the highs on the guitar signal, when turned up it boosts the highs higher than my guitar naturally outputs.
    I am hoping this is a good sign and a step in the right direction.

    When following the schematic found here : http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v3-schematic.gif

    I can confirm that I have 19.3v AC being fed to both LM4001’s I have 26.1v DC coming out of the LM4001’s and into the 78L15 transistor, and I have 14.9v DC coming out of the 78L15 transistor and to the rest of the board.

    My repair knowledge is still pretty limited, but poking around the board with my volt meter. I get 14.9 volts in many places where i should. I have even checked the SAD0124 and I am getting 13.9v on pins 5,7,9,11. 14.5v on pins 8, 10. 3.75v on pins 2 15, 4.16v on pin 12 and 4.49 on pin 6.
    Not sure if any of that info helps but figured i would put it here anyway.

    aside from checking voltages around the board there is really not much else I know how to do. I do own an oscilloscope but i have no clue how to use it. So unless someone can guide me, I can’t really check the actual clock frequencies coming from any of the chips.

    I have even tried adjusting the trim pots around the board and the best i can get from them is either my guitar sound or a horrid squeal.

    I am not sure where else to go with this. It has made some progress since 3 years ago, but still not working as intended. I would give almost anything to get this baby to work again. If anyone can help me further in this quest I would be so appreciative. I can post all the pictures you want if needed.

    Thanks.

    #119260
    The EH Man
    Moderator

    Audio probe the input pin of the SAD1024 and see if you’re getting signal to it. If you are, audio probe the output pin for signal. That’ll narrow down the area.

    #119261

    which pins would those be?

    #119262

    i get my guitar signal on pin 2, 15. nothing on 6 and 12. so im assuming the SAD1024 is shot? if so is it possible to replace? also if the SAD1024 was fried, wouldnt i get no signal through the flanged output at all? or does the flanged effect mix with a dry signal or something?

    #119263
    The EH Man
    Moderator

    Have you checked your voltages to see if it’s around 15v?

    #119264

    Yep, mentioned that in the first post

    ” I have even checked the SAD0124 and I am getting 13.9v on pins 5,7,9,11. 14.5v on pins 8, 10. 3.75v on pins 2 15, 4.16v on pin 12 and 4.49 on pin 6.”

    sound goes in on pins 2 and 15, and no sound coming out on 12 and 6 even tho it shows there is some sort of voltage there.

    also getting 14.5 – 14.9 volts at random places throughout the board. basically anywhere after the first transistor.

    Thanks for your help and quick replies by the way. I soooo want this thing to work again.

    #119270

    ok so i found an SAD1024 for sale but its going to cost me about 50$ so given all the information above what is the likely hood that this will fix my unit? Should I buy it, or are there any other expense parts which could be the problem that I am aware of? after the SAD1024 chip it’s just fairly cheap capacitors, diodes, resistors and a few cheap IC’s right?

    #119305

    anyone? as far as I can tell, the trim pots need to be realigned and the SAD1024 chip replaced and the pedal should work again. I have read that there are a few people who can do this. Anyone know roughly how much this would cost if i supplied the SAD1024 chip? I have the chance to buy a V4 reissue for 100$ so I’m trying to weigh whether it would be better to just buy that or get mine fixed. Does the V4 sound much different than the one I have?

    #119306
    Stephengiles
    Member

    14.5v on pins 8, 10 is not good so the clock is suspect – it should be around 7-7.5v with the same voltage on pins 3 & 14. I would replace both the LM311 and the 4013 before spending out on the BBD. Good luck – EH should know that!!!

    #119307
    Quote:
    14.5v on pins 8, 10 is not good so the clock is suspect – it should be around 7-7.5v with the same voltage on pins 3 & 14. I would replace both the LM311 and the 4013 before spending out on the BBD. Good luck – EH should know that!!!

    Could that simply be because the trim pots are all out of whack?? or does that have nothing to do with the trim pots?

    #119308

    also before i go replacing these IC’s am i going to damage them by putting them in this thing if something else is out of whack? I dont really want to buy stuff if the problem is further up the line and im just going to fry them by putting them in.

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