Electric Mistress V2 1977 HELP

[brokenstarguitar]

Ok I have an Electric Mistress V2 (1977 I believe) with the Mick Davis mods. Now i dont get any sound out of it. If i turn it all the way up i can hear is "whooshing" but vary faintly which makes me think the chip is fine. Ive went over everything, even playing with the trimmers. I even swapped out the Rate pot but i get the same issue. What could be wrong with it? Caps maybe? Id rather not do more than I have to since Mick worked on it himself. Heres a few pictures

[theehman]

Check your voltages and see if you've got around 13.2vdc on pin 8 of the 4558.  Check for signal on the 4558 pins 1 and 7.
Just because Davis worked on it doesn't make it special.  I've seen some horror stories come out of his hands.

[brokenstarguitar]

Not sure i did it right so i put up a picture showing what i used on my DMM. Voltages as follows on the 4558... I think i did something wront with the dmm cuz i didnt get anywhere you said i should be. Could it be a bad 4558?

Pin1: .35
Pin2: .33
Pin 3: .24
Pin 4: .12
Pin 5: .13
Pin 6: .30
Pin 7: 30
Pin 8: 30

Check your voltages and see if you've got around 13.2vdc on pin 8 of the 4558.  Check for signal on the 4558 pins 1 and 7.
Just because Davis worked on it doesn't make it special.  I've seen some horror stories come out of his hands.

[antonis]

That DMM setting is for AC voltage measurement...
Tthe next one (solid & dotted line) is used for DC ..

[Rob Strand]

Pin1: .35
Pin2: .33
Pin 3: .24
Pin 4: .12
Pin 5: .13
Pin 6: .30
Pin 7: 30
Pin 8: 30

That DMM setting is for AC voltage measurement...
Tthe next one (solid & dotted line) is used for DC ..

And with those measurements and that setting you would have to question what is going on!

Options:
- The meter wasn't on that setting for the measurements!
- The meter was on that setting and something is wrong with the power supply.
   Perhaps the filter caps are dead.  [Doesn't look like that model has any.]
- Also I thought those unit had a regulator.   30V at the IC means the regulator could be blown.
   (Can't find a decent schematic quickly on the web with the PSU section drawn; it used to be easy.)
- Check type of adaptor matches the device.

Start by measuring the DC voltage across the main filter cap.
Next measure the DC voltage across the IC.

Look for a TO-220 regulator on the PCB.

A few meters can measure DC on the AC range; "total" rms.  The manual for that meter shows
it is not one of those types of meter.

The earlier one does not have a To-220 regulator.  It's got a discrete regulator with a LM741 (IC5 on schem). 
The LM741 is powered from the input DC rail so that could be 30V.
30V could mean the regulator transistor is blown.

http://metzgerralf.de/elekt/stomp/mistress/index.shtml
http://metzgerralf.de/elekt/stomp/mistress/images/1976-electric-mistress-v2-schematic.gif

[brokenstarguitar]

I tried the DC but theres multiple options. So i picked the one without the "-" symbal.

Pin 1- 680
Pin 2- 240.00
Pin 3- 76
Pin 4- 84
Pin 5- 79
Pin 6- 196
Pin 7- 191
Pin 8- 187

I still dont think im using it right but when i try the other settings i get "0". Is there a specific setting i should be using? I did notice theres no ground. Should i check other places, replace the  caps or replace the 4558?

[theehman]

Here's where to check for your 13v

[Rob Strand]

I tried the DC but theres multiple options. So i picked the one without the "-" symbal.

Get a 9V battery and measure that first.  Find the DMM setting that produces 9V.   You need DC for sure.   Preferably auto ranging.

The '-' symbol just means the voltage is negative.  If you expect positive voltage and it shows negative, just put the negative (black) probe where the positive (red) probe is and visa versa.   Try swapping the probes with the 9V battery.

FWIW,  my gut feeling is there is a problem with the power supply and it's pretty much reading 0V.   I suspect your multimeter is autoranging to mV (1/1000th V); so a reading of 30 is 30mV.    If you look at the side of the meter display you might see the units are "mV" and not "V".

Manual Page 6 (not very clear),
https://emimikos.gr/shop/Documents/MS8268_P1.pdf

[brokenstarguitar]

These are the settings on the dmm

[DrAlx]

So most of those pics have mV as the unit, but the last one says 261 V.
How are you powering that pedal?
I suggest you not plug in any sort of adapter and instead just use 2x 9V batteries.

[Rob Strand]

To get 261V I suspect the multimeter has a bad switch.

[brokenstarguitar]

Ill get batteries tomorrow.

[brokenstarguitar]

Ok guys, my dmm seems not to be working correctly so i cant take voltages so i probed it. I get no signal anywhere except down by the Redicon ic. I dont even get a signal at the 4558 or the input jack.  Heres a quick video of where im getting audio.

Let me say that my guitar (signal) is no where to be heard, just the "swooshing" of the chips.

https://youtu.be/XpcInwdWXWA

[theehman]

Ok guys, my dmm seems not to be working correctly so i cant take voltages so i probed it. I get no signal anywhere except down by the Redicon ic. I dont even get a signal at the 4558 or the input jack.  Heres a quick video of where im getting audio.

Let me say that my guitar (signal) is no where to be heard, just the "swooshing" of the chips.

https://youtu.be/XpcInwdWXWA

If you're not hearing guitar at the input jack or where the input goes to the pcb, you may have a shorted jack.

[idy]

If you find the signal at the Redicon (sic) but not at the input jack, you are doing something wrong. You are confused.

The video, well doesn't tell much... but assuming that tone we are occasionally hearing is your "signal generator" (?)... we would then know that signal was getting in through the input jack.

If signal is reaching the Reticon, it must be getting there through the 4558. You would almost certainly be finding the signal at pins 1,2,3 and 5,6,7 of that chip.

From there it goes to the 1024. In pin 2, out pins 5 and 6. In pin 15, out 11 and 12.
No need to look for signal elsewhere. You won't find it. Maybe a swooshing of clock rate artifacts...

You will not (should not) find signal on any other chip. Not the 4013, not the 741, not the LM339. Don't bother looking for it there.

[brokenstarguitar]

Im actually using a Ditto as my signal generator, that swooshing isn't what i recorded through the ditto, not even close.

I also probed everything, top and bottom (once in bypass and once on, still getting no signal either way),. The only place i get signal is when i touch those few spots in the video and its NOT my signal from my looper.

[idy]

The only place i get signal is when i touch those few spots in the video and its NOT my signal from my looper.

So to clarify, you are using a looper with something like "music" on it as a signal, and the tone we are hearing on a few pins is not your signal? So don't call it signal. It's something from the oscillator/clock. But I do hear whooshing, which implies some flanging going on, maybe.

OK, so why isn't you signal getting to your input jack? Easier to figure that out than to go probing around an innocent and expensive and obsolete SAD 1024. Until you figure that out it is silly to probe randomly around a complicated board. Signal to jack, jack to, 4558, you would get dry signal out even if every other chip was fried.

And you owe it to yourself to sort the meter business out. If it broken, the world is full of cheap meters that are better than nothing. If it is not broke, learn what the settings mean, learn to use it.

[idy]

Have you looked at the manual for the meter: I mean looked inside, read at least a bit? Do you know how the "range" function works? The DC volts setting, then range for volts or millivolts, press and hold the button for auto range mode...

Being able to read the voltages of the chips is the next thing after figuring why the signal is not getting from your cable to the tip of the in jack and to the board.

People don't know what you don't know, what knowledge is missing. So to bell helpful we have to ask basic questions. Ask us how many of us had been stumped by an "obvious, newbie, silly" mistake. When you measure voltages the black probe needs to be on a good ground. I like to use an alligator clip so I can concentrate on the red or "business" probe. We haven't seen you whole pedal. Are the jacks grounded? Do they have ground wires to them or are they "grounding through the enclosure?" Bad housekeeping, but people did things like that.

Astonished the peeps have not begged for a nice picture of the thing you are working on.

[Rob Strand]

Ok guys, my dmm seems not to be working correctly so i cant take voltages so i probed it

Some common problems:
- dmm fuse blown.
  Check the dmm fuse.
  If it is a ceramic fuse and not a glass fuse it's hard to see if it is blown,
  you need another dmm (or use another method like a lamp).
  On some meter all the ranges stop working when the fuse blows but on others only some ranges stop working,
  so it's best to check the fuse first.
- meter leads damaged or open circuit: 
  The way to check is to set the dmm to the ohms (200 ohms) range.
  Short the meter leads together.
  You should see less than 1 ohm, preferably 0.2 ohm or less but it depends on the initial dmm lead quality.
  (an open circuit reading can be the leads or the fuse.)
- flat battery. 
   Normally the battery low indicator comes on but on rare occasions some meters misbehave on some ranges
   before that occurs.  I don't think that's your problem.
- dmm switch intermittent or faulty. 
   This happens often these days (any cheap meter produced after 2000).
- soldering the between the dmm sockets and the dmm PCB cracked/open/intermittent.
   This happens often these days (any cheap meter produced after 2000).

I think it's worth doing the ohms check on the meter leads and to check the dmm fuse.