Home › Forums › Vintage EHX › 18v Electric Mistress Troubleshooting Questions

Viewing 13 posts - 16 through 28 (of 28 total)
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  • August 6, 2016 at 10:53 pm #121817
    nedblau
    Member

    Ok, will measure. I only bought the SAD 1024 because I found one relatively cheap. I figured if I didn’t use it I could sell it pretty easily. If it turns out I don’t need it, I’ll offer it here for $85, the same as I paid. I couldn’t find very many for sale anywhere, and the went from $100-$125 used to $150 for NOS. I did find $25 SAD512s though.

    August 6, 2016 at 11:33 pm #121818
    nedblau
    Member

    Well, there’s voltage on all the ICs at least. How am I looking?

    741

    1) 0
    2) 3.3v
    3) 1.62v
    4) 0
    5) 0
    6) 1.21v
    7) 3.45v
    8) 1.6mv

    4558

    1) 1.4v
    2) 1.4v
    3) 1.35v
    4) 0
    5) 1.36v
    6) 1.4v
    7) 1.4v
    8) 3.3v

    1024

    1) 0
    2) 1.5v
    3) 1.7mv
    4) 0
    5) 3.59v
    6) 0.1mv
    7) 3.57v
    8) 0.42v
    9) 3.6v
    10) 0.42v
    11) 3.57v
    12) 0.1mv
    13) 0
    14) 3.2mv
    15) 1.49v
    16) 0

    7611

    1) 0.42v
    2) 0.42v
    3) 0
    4) 2.09v
    5) 0
    6) 23mv
    7) 0
    8) 0
    9) 0.42v
    10) 0
    11) 2.14v
    12) 0.44v
    13) 3.4mv
    14) 3.6v

    339

    1) 2v
    2) 3.6v
    3) 3.6v
    4) 0.43v
    5) 1.92v
    6) 0.92v
    7) 2.64v
    8) 25mv
    9) 1.52v
    10) 3.64v
    11) 122mv
    12) 0.1mv
    13) 23mv
    14) 0.92v

    August 6, 2016 at 11:42 pm #121819
    Scruffie
    Member

    Right, you see pin 8 of the 4558? That’s your voltage for the circuit at the moment, it’s currently 3.3V but should be in the 12-13V range, better than it was before but something’s still wrong.

    But… Pin 7 of your 741 should be your supply voltage of 18V and is only 3.45V, how are you powering the pedal? In your previous voltages it was at 18.8V so possibly you made a mistake with the mods and something’s dragging it down.

    August 7, 2016 at 1:01 am #121821
    nedblau
    Member

    I’ve been using batteries. I need to do the voltages again, because now I’m getting 15v on pin 7 of the 741 (with worn batteries) and nearly 22v with an 18v power supply. I know power supplies look higher than they should when unloaded, but 22v from an 18v wall wart seems out of line. Anyway, I’ll do the voltages again tomorrow. Thanks for hanging in!

    August 7, 2016 at 5:46 pm #121823
    nedblau
    Member

    This time I used the 18v wall wart instead of the batteries.

    741

    1) 0.1mv
    2) 6.6v
    3) 6.8v
    4) 24mv
    5) 5mv
    6) 14.2v
    7) 23v
    8) 8mv

    4558

    1) 6v
    2) 10mv
    3) 8mv
    4) 0
    5) 6v
    6) 6.1v
    7) 6.1v
    8) 14v

    1024

    1) 0
    2) 6.1v
    3) 3mv
    4) .3mv
    5) 14v
    6) 3.4v
    7) 14v
    8) 12v
    9) 14v
    10) 12v
    11) 14v
    12) 3.4v
    13) 0.3mv
    14) 3mv
    15) 6.1v
    16) 0

    7611

    1) 3.9v
    2) 3.7v
    3) 0.3mv
    4) 8.2v
    5) .3mv
    6) 236mv
    7) 0.4mv
    8) 0.4mv
    9) 12v
    10) 0.4mv
    11) 7.1v
    12) 12v
    13) 5mv
    14) 14v

    339

    1) 7.1v
    2) 14v
    3) 14v
    4) 3.8v
    5) 7.4v
    6) 5.6v
    7) 10.1v
    8) 97mv
    9) 6.2v
    10) 14v
    11) 0.47v
    12) 0.5mv
    13) 235mv
    14) 5.7v

    August 7, 2016 at 6:50 pm #121824
    Scruffie
    Member

    Muchhh better.

    Right, there’s a problem with the 4558 & 4013 (which you’ve listed as 7611, which I assume is a date code instead of the part number).

    On the 4558, pins 2 & 3 should be 6V like pin 1, double check the readings on it as in your prior readings while low voltage they were correct in relative terms.

    If the 4013 is socketed try popping in a new one and retake the voltages on pins 9, 12 & 13.

    August 7, 2016 at 9:26 pm #121826
    nedblau
    Member

    Awesome, getting closer. I’ll have to hit the parts store tomorrow for a 4013. I’ll send results by EOD tomorrow.

    I could have a bad 4558. I replaced the original with one I had in my parts box. I have many, so I’ll try another one.

    August 11, 2016 at 7:15 pm #121842
    nedblau
    Member

    Hey Scruffie, I had to order the 4013 — sorry for the delay. It freakin’ works! I still need to check the voltages to really be sure everything’s okay, but I put in the new flip-flop and a new 4558 and it flanges. It’s obviously noisy, but there’s also some grit in there that seems out of place. Any suggestions? Maybe a bad resistor? Anyway, I gotta do real work now, so I’ll post revised voltages later today. Woohoo!

    Edit: this is with the old SAD1024 chip. Bonus!

    August 11, 2016 at 8:50 pm #121843
    Scruffie
    Member

    Awesome! :)

    Hmm… when you say grit, what do you mean exactly? Is it distorting? That may just mean you need to tweak the bias trimmer properly.

    If it’s a ‘chirping’ noise that’s due to the low filtering and the BBD not running in parallel multiplex which improves the sampling, it can be cured though with some minimal high loss and an easily reversible mod by tacking an 820pF to 1n cap in parallel with the 6k8 in the feedback loop of the 4558.

    A bad resistor is unlikely, there’s no electros or tantalums in the audio path either (at least when the pedal is engaged) that could have gone dry, although replacing the ones related to power might cut down on some noise and is probably worthwhile as they’ll eventually go dry and changing them wont affect the tone so it’s just one less thing to worry about going wrong down the line. The only other thing I can think of would be a loose solder joint so checking the board over and touching up any that look a bit iffy may be worth while.

    Congratulations on getting it going again, hope you enjoy it.

    August 11, 2016 at 10:30 pm #121844
    nedblau
    Member

    I still haven’t had a chance to confirm voltages, but I did play with it a little at lunch. The static/grit is associated with the Range control — more range, more static. I’ll tweak the pots on the board and update…

    August 16, 2016 at 10:55 pm #121864
    nedblau
    Member

    Finally done with pesky work and back to what’s truly important. So, pins 2&3 on the 4558 were both 5.8v. Pins 9, 12, & 13 on the 4013 were all hovering around 6.85v. Does that seem right to you? I haven’t had time fool around with the pedal since the last time I posted, but I did notice something odd — when the bottom is off the pedal case and the pedal is upside down, I get a very clean signal. When the pedal is assembled and right side up, I hear a lot of gritty whoosh at one point in the sweep. I have several BBD flangers and this is noisier than normal.

    August 16, 2016 at 11:05 pm #121865
    nedblau
    Member

    She’s a real closet queen…

    August 16, 2016 at 11:19 pm #121866
    nedblau
    Member

    Well, silly me. The noise issue was apparently caused by one of my guitars! It has super high gain old Japanese single coils, and I guess the Mistress didn’t like it. I just tried it with my Strat and it’s much better. Go figure. Scruffie, thanks again for all your help and positive vibes.

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