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So... Years ago I've bought this great flanger from an a**hole that screwed up all the trim pots, breaked the switch, cuted cables, etc...
I repaired it and tried to get back the trimpots to the best position.

I've readed a lot of threads about it, even this: http://www.metzgerralf.de/elekt/stomp/mistress/align.shtml#4
But, I'm far from somebody that have a oscilloscope

Anyone had the same experience?

Can anyone share the stock trimpot values?

I know that there are no set positions, each is adjusted to the correct values for each individual pedal.
But, I think some value can leave me closer.

You don't need a scope to set the clock trim. You can do that by ear.

http://www.diystompboxes.com/smfforum/index.php?topic=91981.msg1047491#msg1047491

You can do BBD bias by ear too. Bias pot too far left or right will stop the sound going through the BBD. So you just twiddle the pot to find those two extremes and set pot half way. Then play notes. If the are distorted, tweak a bit more left or right till distortion is gone.

Feedback pot is set to prevent the thing oscillating when color is high. You set of so there's is no oscillation at max color for all possible range values in filter matrix mode.

I would set BBD bias first.
Then clock trim.
Finally the regent/feedback pot.

As a very rough guide to do it by ear, set it to the filter matrix mode, feeback at half way, range all the way up, rate down.

Set all the trimmers to 50%, to start with and then feed an audio source (guitar, mp3 or whatever but it will need to be continuous) in to the pedal and adjust the bias trimmer until you hear the delay signal passing, it should have a small range where it works and then tweak it for the least distortion (if you have an audio probe, probing the output of the BBD will make this easier to hear) if you encounter oscillation, back off the feedback trim a little.

Then if you have a multimeter with a Hz setting, probe pin 1 of the 4013 and adjust the clock trimmer for 40kHz, if not, you'll have to adjust it to where you think it sounds best (delay sound not too sproingy or noisy) and tweak it as needed after you finish setting up.

Next adjust the mix trimmer, you'll want to turn the feedback control all the way down now and this is where an audio probe would be very useful (instructions to build one are in the debugging page tab above) and adjust for a 50/50 mix of dry and wet signal at the output.

Finally, turn the colour control all the way up and adjust the feedback trimmer until just before the point of oscillation.

Or do it how DrAlx posted while I was writing this :D

Wow.... you guys are genious!
With all your advises, ASAP I get home, I'll try.

I'll use the note between C# and D, in A string.

Thanks a LOT!

To update!
Ok ... I made the alignment with his advice.
The pedal works fine now!

Conclusions:
- BBD bias: it is where it stops sounding, and where to make the sound "distort" a bit. But I'm not sure; It did not distort in much rank. There is no fixed value / voltage for this?
- Setting the clock: put a bonnet on the 4th fret, and slightly adjust to the peg to get that C#/D in between note. Hit with a screwdriver the pickup and tune the trimpot with the string note.
- Mix: all the way up... what the hell...  ;D
- Feedback: Colour at max, and set where the oscilation stoped.

I have my doubt's with the BBD bias.... :-[
It's like the college exams where all the exercises are related; and if you fail the first one, all the others are wrong. Even if you make that right.  :icon_rolleyes:

If the BBD bias is turned totally clockwise or totally anticlockwise you will get either nothing through the BBD or distortion. There is a small range of  trimpot settings somewhere between those two extremes that works best and let's the signal through with minimum distortion.
If you had an oscilloscope you would input an audio sound wave, either sine or triangle, and then turn the bias pot to the position that gives the least distorted output wave.  You don't have a scope so have to use a combination of your eyes (by looking at the angle of the trimpot setting) and you ears (to listen for distortion).
To give the signal the best chance of making it through the circuit undistorted, you need to set the color (feedback) to minimum, use filter matrix mode. Also put the range pot near the middle so it is not at an extreme setting. Play a clean guitar signal into the pedal. There will be a small range of bias settings where the signal out of the BBD will sound OK. E.g. if you from find that the bias sounds OK for bias pot angles between 4 o'clock and 6 o'clock then you would put the bias at 5 o'clock.

Thanks again Alex.
This afternoon I'll put my amp as loud and clean as I can, and make it the most accurate as possible.

I'll keep you informed  :)

Quote from: DrAlx on February 17, 2017, 07:03:37 PM
If the BBD bias is turned totally clockwise or totally anticlockwise you will get either nothing through the BBD or distortion. There is a small range of  trimpot settings somewhere between those two extremes that works best and let's the signal through with minimum distortion.
If you had an oscilloscope you would input an audio sound wave, either sine or triangle, and then turn the bias pot to the position that gives the least distorted output wave.  You don't have a scope so have to use a combination of your eyes (by looking at the angle of the trimpot setting) and you ears (to listen for distortion).
To give the signal the best chance of making it through the circuit undistorted, you need to set the color (feedback) to minimum, use filter matrix mode. Also put the range pot near the middle so it is not at an extreme setting. Play a clean guitar signal into the pedal. There will be a small range of bias settings where the signal out of the BBD will sound OK. E.g. if you from find that the bias sounds OK for bias pot angles between 4 o'clock and 6 o'clock then you would put the bias at 5 o'clock.

That's the way I used to do it.

So, I have good news.
I think I finally have it. :)

But there's something that I noticed: the sound start when I pass the half way on BBD bias trimpot.
Totally clockwise: distort a lil' bit.
Half way, to totally anticlockwise: clean sound.

I mean: 50% no effect, 30% the same good effect, and the last 20% a bit distorted.
So, as you recomended, I leave it at the halfway of the good effect sound, it is at 2 hours, like in this pic:
(http://i47.photobucket.com/albums/f191/krinor/DeluxeElectricMistresstrimpots.jpg)


As I can figure out, the most critical one, is the fine tuning clock.
Now, I feel the flange is like "armonic".

I'll keep playin it this days and see if they're fine  ;D

Thanks a lot!!!

> 50% no effect, 30% the same good effect, and the last 20% a bit distorted.

Play louder (more signal IN to the Mistress). The "30% the same" will now show some distortion. Trim for largest signal with least distortion. It isn't critical, but there will be about a 10% span that is "best". It will very-likely be just about the center of your "30% good" range, so you could just center there and get on with the music.

Quote from: PRR on February 19, 2017, 12:09:05 AM
> 50% no effect, 30% the same good effect, and the last 20% a bit distorted.

Play louder (more signal IN to the Mistress). The "30% the same" will now show some distortion. Trim for largest signal with least distortion. It isn't critical, but there will be about a 10% span that is "best". It will very-likely be just about the center of your "30% good" range, so you could just center there and get on with the music.

I'll try again as louder as I can  ;)

Hi Everyone.

Brand new to the forum and I didn't want to start a new post as I feel like the knowledge from the members posting to this topic can help!

I have a 1978 DEM Version 1 with an issue I believe is trimpot related (but could be wrong).

Here is the issue:

When the effect is engaged and the Flanged Output is being used there is an audible loud hum sound. However every 10 seconds or so, it goes away and the beautiful flanger sound comes through for a split second before the hum returns. The best way I can describe it is that the effect is not audible and the dry signal is heard for 10 seconds of playing and then for an instant the wet signal kicks is and the loud hum stops before reverting back.

I am by no means knowledgeable about these but I have checked all the connections for soldering breaks or bad connections etc. Everything internally appears to be in place.

Would anyone know specifically if a trim pot adjustment to a certain pot would be the correction?

When I adjust the bottom knob I am able to adjust the duration of time between the non Flanged sounds with the hum and the effect kicking in super briefly.

It's almost like the effect is being blocked from coming through and then the connection aligns for a split second and repeats on a cycle.

Please help!!!

QuoteWhen the effect is engaged and the Flanged Output is being used there is an audible loud hum sound. However every 10 seconds or so, it goes away and the beautiful flanger sound comes through for a split second before the hum returns. The best way I can describe it is that the effect is not audible and the dry signal is heard for 10 seconds of playing and then for an instant the wet signal kicks is and the loud hum stops before reverting back.

Given the clean signal is coming through and it goes noisy when there is no wet signal I'd be looking at things that go open and float in the wet signal path.    The biggest suspect would be the 1k bias trimpot.    Usually you don't get enormous amounts of hum when something on board goes open.

I don't think it's a trim pot issue, with a trim pot i'd expect hiss, whine or distortion.

Hum to me suggests you have a/some bad caps, they're 40 years old now after all and have a limited life span, i'd start with the two large caps in the power section before moving on to the audio path.

Thanks to you both for the quick replies!

I guess before I start to take stabs at anything would the caps be able to temporarily work for a split second and then revert back??

I'm probably explaining it poorly but when the pedal effect  is engaged an audible hum is present which I know these older pedals were louder then modern but the part I am puzzled with is that after 5-10 seconds the hum stops and the flanger sound kicks in for a super short instant and then reverts back to the non Flanged signal and the hum.

My understanding is the Caps would be continual hum regardless and the effect would be audible the entire time?

I was guessing trimpots since the effect is present albeit briefly for that split second on a regular interval. I read somewhere that the position of certain trimpots can block the signal entirely from coming through.

I unfortunately do not have an oscilloscope but i also don't want to send it for service of $100 upwards if it's a simple fix by tweaking a trim.

Does the problem change with the rate setting? And have you measured the voltage from the regulator to make sure it's correct & steady.

Yes. When the rate setting is changed the intervals of time between the hum and non Flanged sound and the instant of no hum and Flanged effect either shortens or lengthens depending on which way I turn it.

So might be 10 seconds of non Flanged signal and hum and 1 second of Flanged no hum at the longest range. And when I turn the knob the other way it's probably 3-5 seconds of non Flanged signal and hum and 1 second of Flanged no hum.

So the period of time the effect is working is unchanged (milliseconds) but the duration of time between when it kicks in and out is shortened or lengthened.

I have a multimeter but was having trouble locating the voltages for the ICs to validate each Pin correctly.

Ah, that sounds like it might be the 1uF tantalum cap off pin 2 of the 311 in this schematic then http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v1-schematic.gif

As long as the 78L15 regulator has a steady 15V on its output pin, it's fine.

(https://s31.postimg.org/n4m5n4ozb/7_D3_C3577-729_B-48_E0-_A7_FF-_CDBC2_DDCD90_F.jpg) (https://postimg.org/image/n4m5n4ozb/)

(https://s31.postimg.org/knaefu2hz/94_CFAB4_B-9170-4_C41-_ADB0-12658376_A075.jpg) (https://postimg.org/image/knaefu2hz/)

These are the readings on the output pin. There were 2 and I'm not sure which one it would be. The reading on the first was steady at 16v. The second was all over the map between 1-3 and changed constantly.

I also pulled the 2 chips and reset them in the plugs as some suggest it can be loose but that didn't help.

The 3 potentiometers are all functioning as i can hear the changes to color and range and rate.

If it still has the original 1978 electrolytic caps, I'd say it's overdue for a new set.

Edit:  Sorry, already suggested, I should read instead of skim.

Well at this point a recapping is logical since 40 years is along time for these ecaps to go.

Are there any recommendations for replacing the 2 ecaps with specific ones.

Looks like the originals to me. ICC 220uF 25v and 250mfd 16v.


(https://s31.postimg.org/fnhjlbwg7/ED0_B72_D7-555_E-4_B10-_B4_CC-_A9219_C26407_A.jpg) (https://postimg.org/image/fnhjlbwg7/)

In those photos I can't see your black lead, you are grounding it to the enclosure when you're taking the readings aren't you? The one with 2.99 should be the output pin and showing 15V. If you are, you should check the AC readings from the transformer.

As for the caps, any old electrolytic with the same value (220uF should be fine for both of them, I wouldn't bother trying to find a 250uF as it's an obscure value) and equal or higher voltage rating will do.

Thanks Scruffie.

Sorry for all the questions. Very new to this stuff.
Yes my measurements were taken by using the black voltmeter connection running ground to the outside of the enclosure.

I was reading about replacing caps and lots of statements about attempting to maintain as close to the original uF rating as possible so that's why I asked about the 220 and 250.

As for the reading of the output pin at 2.99 yes it was taken grounded as described.

If you wouldn't mind, how do I take the AC reading accurately from the transformer?

Thanks again for all your help! Will try to recap first and then continue since those should be done anyways due to age.

Multimeter set to AC, 3 leads go from the transformer to the board, black probe on the middle connection and red probe on the two outer, each should read around 12V.

If that checks out then get all the electros and tantalum caps replaced (the old EHX boards have very flimsy traces so you might want to practice de-soldering first if you're not used to it, a spring loaded sucker is pretty much a must followed by a little wick for the remainders) and then if it doesn't fire up right away you'll need to post up all your voltages.

Okay so I first swapped the 2 ECaps out for new 220uF caps. Same symptoms. Nothing has changed.

I measured the voltage from the transformer. Using the black probe in the middle and the red probe on the right it was a steady 16.4V. Using the black probe in the middle and red probe on the left cable it was a steady 32.6v

Pic attached to confirm.
(https://s31.postimg.org/7rfwf8l47/792_F16_CF-4_E51-4_B95-_BB8_F-767_C0450_A017.jpg) (https://postimg.org/image/7rfwf8l47/)

If it's a bad transformer and plug I've read about converting it to a dc input jack and powering via a pedal power supply. I'm running a voodoo lab pp2+ so that would be ideal.

If there is a recommended simple swap I'd like to do it and just use a standard barrel plug. There is a doubler cable so I could do 18v or 24v if needed.

I'm not sure where or what to get for a boss style input jack.

I don't know how the DEM is laid out, but looking at those wire colors (brown, brown, green), I'd guess that green is the center tap, and you would read ~16VAC from the green to both browns, indicating that the power transformer is okay.  Your 32VAC reading was across the whole secondary, skipping the center tap (16+16=32).

Hmmm.

Well I guess if that's the case and it's not the transformer or plug then I try the tantalum caps next since it wasn't the electrolytic caps. 

I am starting to wonder if the hum issue  and the lack of any flanging is an unrelated issue.

For argument sake if I was to focus just on the fact there is no flanging happening that makes me wonder again about trimpots being a problem.

It almost seems like I have a mild chorus effect happening compared to a direct clean signal.

Your transformer readings are good.

You could start poking at the trim pots but you have a regulator that says it's putting out 3V... that's not a trim pot problem and needs to be taken care of before fiddling with the trimmers because the circuit isn't going to work correctly if that's the case.

Did the voltages on the regulator input or output change at all with the new caps? If not, my next step would be to disconnect the regulator output from the circuit to find out if something in the circuit is pulling it down or if it itself is to blame.

Okay so my next steps today will be to:

1) Re-measure the output of 78L15 output pin to see if the new Electrolytic caps have fixed that issue.

2) If no improvement then swap the 1uF tantalum cap running off Pin 2 of the 311

3) If that tantalum cap replacement works, great. If not then disconnect the regulator (78L15) output pin only? Or remove the entire regulator from the circuit.

4) assuming that none of this corrects the situation I will then post voltages for the ICs


Anything I am missing in the order or should do differently. I appreciate all the hand holding through this :S just trying to get this back to life!

I would go in this order;

1) Re-measure the output of 78L15 output pin to see if the new Electrolytic caps have fixed its voltage issue.

2) Test all the electrolytic/tantalum capacitors on the board for continuity to make sure none are acting as shorts, if they are, replace them then repeat step 1

3) If the issue is not resolved then disconnect the regulator (78L15) output pin from the PCB and measure its input and output voltage, if its input is at least 18V and the output reads ~15V then reconnect the output pin to the PCB, if the output is still too low then the problem is most likely the regulator or failing that, the rectifying diodes.

4) Post voltages

Thanks. I'm going to have to visit my local electronics shop to pick up some pieces.

Would you mind taking a quick glance at the board and seeing if any visual things stand out as suspect?

Photo is before I swapped the 2 Large Electrolytic Caps. For the 1uF tantalum is that the little orange capped one on the immediate bottom left of the 311 chip? You mentioned pin 2 but when I follow that trace it goes to components above the chip (when referencing the photo)


(https://s31.postimg.org/mao07c1lj/A0_C3_FFE5-_C1_C2-43_AA-829_C-_A58_FF4_E01574.png) (https://postimg.org/image/mao07c1lj/)



(https://s31.postimg.org/s08u5c7fb/470052_C8-_E7_F3-4_C80-_B0_BD-_B9_E578_E7_BA30.jpg) (https://postimg.org/image/s08u5c7fb/)

QuoteFor the 1uF tantalum is that the little orange capped one on the immediate bottom left of the 311 chip?

That looks like a ceramic to me.  The orange/red one due north of the LM311 is probably what he was referring to.  Those two blues might be tantalums also.  Tantalum caps are polarized, usually have the + side designated, though often in very small print.

Well. Not so good news.

I replaced the 1uF tantalum cap (it was the red one above the 311)
I also had to replace the 78L15 due to the continued poor reading on output.

New components in. And now there is NO audio when engaged.

What could have happened here?


(https://s31.postimg.org/odg1vu58n/E7335418-574_E-4_EA6-_BA58-3970680_DBACE.jpg) (https://postimg.org/image/odg1vu58n/)

Are you getting 15V out the regulator now it's been replaced? If so, voltages of all the ICs are needed.

No now I am getting 3v out of BOTH the input and output of the regulator.

Also there is no sound happening when the pedal is engaged as if there is a circuit break preventing any signal. All that was changed was the 1uF tantalum cap and the 78L15.

What's the best way to troubleshoot the signal now that nothing is coming through.

You need to stop focusing on the signal and focus on the power first, if the circuit isn't receiving proper voltage, it isn't going to work properly.

So, looking at the schematic we can see there's the transformer, two diodes which rectify the AC power to DC, a smoothing capacitor and then the regulator.

So far you've replaced the capacitor, the regulator and confirmed the transformer has a suitable AC voltage coming out of it but that a suitable DC voltage isn't hitting the regulator and therefore a suitable one will not come out of it.

Which, unless something in the circuit is pulling the voltage down (which is why I had you test the regulator with the output leg disconnected from the circuit board to isolate it) means there's really only two parts left which could be causing the voltage problem, the 1N4001 rectifying diodes.

Did you test the regulators input and output voltage with its output disconnected from the PCB before continuing?

With the 78L15 output removed it was reading correctly for input and output. But when it was reconnected both input and output dropped to approx 3-4v each.

Ahh, okay, now we're getting somewhere then :)

So that tells us something on the board is pulling the voltage down as it's gone bad.

As it's in a socket and it's easy to to try, try pulling out the 4013 and see what happens to the regulators output voltage.

If that doesn't bring it back up to where it should be you'll need to take voltage readings, start with the 741 and 4558 first.

Okay so with the 4013 Out we have 3.6v in and 2.9 out.

With it back in 3.4v in and 2.7v Out.

741 voltages

1. 0
2. 7.0
3. 6.0
4. 0
5. 0
6. 6.5
7. 17
8. 0

4558 voltages

1. 5.1
2. 5.1
3. 4.6
4. 0
5. 6.8
6. 7.1
7. 7.1
8. 17

Well something funny is happening here, you say your regulator is giving out 3V, but your opamps are showing they are getting 17V... which is higher than it should be.

The voltages on those look fine other than that, what are your voltages on the 4013, 311, & 324.

The 4558 is biased by the SAD1024 output voltage so for now we'll assume it's not the problem.

Edit: You have checked the pedal is grounded to the enclosure haven't you... that might explain the strange readings, if you use a ground point on the PCB (the middle pin of the regulator would do) for the black lead of your multimeter and check the regulator output that way.

(https://s31.postimg.org/lkwhmq5rb/ED5_F5_DB6-_FD3_B-4_B3_A-_B7_E8-286211485471.jpg) (https://postimg.org/image/lkwhmq5rb/)

So this is the regulator i am measuring. Output is 2.7v and input 3.4v. Circled in red.

When I go and use the middle pin ground of this regulator as a reference ground the readings are dropping. So I used the ground of the other 78L15 (not circled in the photo) and it results in the 2.7v and 3.4v which matches when I use the enclosure.

Would there be a problem with this regulator in red? I bought a spare if needed.

4013 voltages

1. 7.3
2. 7.3
3. 7.7
4. 0
5. 7.4
6. 0
7. 0
8. 0
9. 0
10. 0
11. 0
12. 0.02
13. 16.9
14. 16.9

311 voltages

1. 0
2. 3.8
3. 2.7
4. 0
5. 17
6. 17
7. 7.7
8. 16.9

324 voltages

1. Cycling between 0 and 16
2. 7.4
3. Cycling between 4 and 10
4. 16.9
5. 1.95
6. 1.99
7. 3.9
8. Cycling between 0 and 9
9. 7.4
10. 7.4
11. 0
12. 1.9
13. 1.9
14. 1.9

I'm using the V1 schematic from this great collection:
http://www.metzgerralf.de/elekt/stomp/mistress/index.shtml
http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v1-schematic.gif

I don't see how you can get 17V from a 15V regulator without something being wrong.
Maybe the regulator was installed the wrong way around?

QuoteSo this is the regulator i am measuring. Output is 2.7v and input 3.4v. Circled in red.

I looked at the PCB and I suspect the part marked with the RED circle is not the regulator.
To me it looks like the lower part nearer to the diodes and the two big caps is the regulator (making the RED circled part the transistor).

(https://s31.postimg.org/6dl3gc0s7/ABF880_F7-2_E59-4_C11-9747-_CDDD7736880_D.jpg) (https://postimg.org/image/6dl3gc0s7/)

Based on the schematic you mean this?

QuoteBased on the schematic you mean this?

Yes.

You should also confirm it yourself like this:
- Look at the schematic find the two diodes on the left.
  Now look at the PCB and find the diodes the transformer wires connect to.
- On the schematic notice the two diodes connect together then connect to the regulator.
  On the PCB find the track where the two diodes connect together then go to the regulator.
  (Confirm also that it goes to the correct pin of the regulator.)

You should also be able to confirm the part number marked on the device.
However, you should check the part via the PCB connections, as I mentioned before.

(https://s9.postimg.org/qaj02loln/mistress_v1_power_trace.png) (https://postimg.org/image/qaj02loln/)

Thanks for the help and clarity.

Sorry was my bad on mixing the 2 up and not checking the board clearly.

Okay so the reading on the output are 19.3v and 17.8v input on the regulator.

The transistor is reading at 2.7v output and 3.4v input.

All the voltages posted above are still unchanged for the 4013 and 311 and 324.

Pins 1,3,8 on the 324 do not hold a constant V.

QuoteOkay so the reading on the output are 19.3v and 17.8v input on the regulator.

The output at 17.8 volts looks bad it should be 15V.
You could check the soldering on the ground pin of the regulator.  Perhaps touch it up.

QuoteThe transistor is reading at 2.7v output and 3.4v input.

Not sure what input and output is.
Look here
https://upload.wikimedia.org/wikipedia/commons/4/41/Transistor_PNP_symbol.png

B = base, E = emitter, C = collector.

From what I can see:
- the base should be about 1.5V off the +V rail.
  So for your +V=17.8V,    (Keep in mind +V should be +15V)
  base = 17.8 - 1.5 = 16.3V
- the emitter should be about 0.65 V higher than that. So about 16.3V + 0.65 = 16.95V
- The collector is connected to pin 3 of the LM 311 so that will be at 2.7V based on you previous measurements.
  It looks *roughly* right as it should be close to the voltage on pin 2 of the LM 311 which is 3.8V.
  I would of expected slightly better match but it's not really a place to be probing with a multimeter
and getting a precise value.

So to me, your transistor E and B voltages look wrong.

The other thing to keep in mind is the switch position.  On one position the voltage in pin 3 of the LM311 will be constant on the other it will move around like the LM324 voltages.

Just to clarify something,   before you said you replaced the 78L15  did you put the new regulator in the transistor position or in the regulator position on the PCB?

Quote from: Rob Strand on April 08, 2018, 04:18:40 AM

Just to clarify something,   before you said you replaced the 78L15  did you put the new regulator in the transistor position or in the regulator position on the PCB?

What I was about to ask, would explain why you stopped getting audio after replacing it and also probably indicate the regulator is in fact bad if it's putting out 17V.

Other than the supply voltage, the voltages you've posted look within range for the IC's.

Okay so I definitely replaced the wrong spot. I put the new 78L15 in the spot circled in red.

It should have gone into the spot circled in green.

At this point to correct the issue given the readings being too high I have another 78L15 spare.

Steps should be to swap the new 78L15 in the green circled space.

What about the one in the transistor position I already changed.

Sorry I realize this was a simple mistake and trying not to waste the help I'm getting by misguiding the process I took. I really appreciate the help here!

Thanks to you both!


(https://s31.postimg.org/y7h0dipxj/DE4524_BE-_DF1_F-4_DF4-8_BC3-_D6_BDA6_A4_CB76.jpg) (https://postimg.org/image/y7h0dipxj/)

These things happen, even to the best of us, main thing is we've caught it and can carry on debugging.

The transistor you replaced by mistake would have either been a 2N5087 or BC309 (check which as the pinouts are opposite IIRC) either put back the original transistor, you can do a quick and dirty test to see if it gives you a reading on the hFe setting of your multimeter to check it's not fried or replace it with a new one.

If you threw it out you need to check the datasheet for the replacement you get to find out the pinout and then trace the connections vs. the schematic to make sure you orient it correctly.

I will have to get a replacement 2N5087 as I don't have a spare. Will be delayed till Monday.

Thanks guys!

Also my local electronic store doesn't carry certain items.

Noticed the regulator is a 78L15A.

Am I running any issues replacing with a 78L15. Haven't done it yet.

Here's how I see the transistor orientations.   You pics seems to match the 2N5087 orientation.
(https://s9.postimg.org/p29toqobv/mistress_v1_transistor.jpg) (https://postimg.org/image/p29toqobv/)

You could use any transistor for now just make sure it's in the right way.  The part isn't that critical.

What happened to the old one?  It was probably good.   And the trimpot is set to match that part.
Technically you need to tweak the trim-pot to match the transistor.

Interestingly the schematic shows 62k but the pics seem to have 82k.

Quote from: Rob Strand on April 08, 2018, 06:34:02 PM
Interestingly the schematic shows 62k but the pics seem to have 82k.

Definitely looks like 62k on my screen, I have a red light filter though so maybe that's bringing out the colour better.

QuoteWhat happened to the old one?  It was probably good.   And the trimpot is set to match that part.
Technically you need to tweak the trim-pot to match the transistor.

True but with component drift and cap replacements, that probably needed to happen anyway.

QuoteDefinitely looks like 62k on my screen, I have a red light filter though so maybe that's bringing out the colour better.

Actually when I look at the zoomed image it looks like 62k.  It's definitely a pure blue.

So

Regulator is now giving reading of 15v input and 22v output.
Transistor is E:14v C:1.5-2.7 cycling.

The regulator was replaced with a 78L15 and original was 78L15A

QuoteRegulator is now giving reading of 15v input and 22v output.

22V in and 15V out - yeah?

More importantly is it working?

So there is now NO signal coming through.

Not even the direct output jack which was working before without issue.

I rechecked that the transformer is still putting out 16v to each cable.

I tried flipping the switch between the filter matrix and flanger and no signal through either.

Not sure how to proceed.

QuoteNot sure how to proceed.

If there's no direct signal there's a chance IC1a and/or IC1b is not biased correctly. 
You will find the DC voltage at the output is stuck at the supply rail or ground.
http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v1-schematic.gif

If the DC at the output of IC1b is off maybe the bias trimpot needs adjusting.   IC1a will probably be off as well.
If only the DC at the output of Ic1a is off then maybe the gain trimpot is off.

[Edit:  Another thing, the cap you replaced, make sure it is in the correct way around.   If it's a tantalum put in the wrong way it will stuff-up the DC voltages.]

Rob is right about checking that tantalum polarity, especially as before you replaced it you were getting some signal.

Your IC1 (4558) voltages look okay to me though and I wouldn't touch any of the trim pots just yet, if anything i'd suspect the 741.

I think now it's time to build an audio probe, assuming you don't have a scope you'll need it for re-biasing later on anyway.

But that's excellent your supply voltage is now correct.

QuoteYour IC1 (4558) voltages look okay to me though and I wouldn't touch any of the trim pots just yet, if anything i'd suspect the 741.

I was thinking since the unit had been modded incorrectly and now put back to a good state, it would be worth re-measuring some of the DC voltages.   Basically we need to start again.

Fair point but I was more looking at them relatively, they're how i'd expect a working opamp to show even if the bias may be off now but the 4558 is disconnected in bypass and from the direct output jack and the 741 voltages while okay are slightly off and is always hanging off the input.

Having said that the 741 is biased by the 4558 so yeah, voltages on the 4558 & 741 again would be a good idea.

From the top here we go.

16.5v from transformer to both brown leads.

Regulator has 14.9v on the OUTPUT pin
Regulator has 22.1v on the INPUT pin.

Transistor has 13.9v on the E
Transistor has 2.5v on the C

SAD1024A voltages

1. 0
2. 4.3
3. 7.3
4. 0
5. 14
6. 6.4
7. 14
8. 7.2
9. 14
10. 7.2
11. 14
12. 6.3
13. 0
14. 7.2
15. 4.3
16. 0

SCL4013BE

1. 7.2
2. 7.2
3. 14.2
4. 0
5. 7.3
6. 0
7. 0
8. 0
9. 0
10. 0
11. 0
12. 0
13. 14.6
14. 14.6

LM311

1. 0
2. 3.5
3. 2.5
4. 0
5. 14.6
6. 14.6
7. 14.2
8. 14.6

RC4558

1. 4.3
2. 4.3
3. 3.9
4. 0
5. 5.8
6. 6
7. 6
8. 14.6

LM324

1. Cycling 0-13
2. 6.4
3. Cycling 4-8
4. 14.6
5. 1.7
6. 1.7
7. 3.6
8. Cycling 4-8
9. 6.4
10. 6.4
11. 0
12. 0
13. 1.7
14. 1.7

UA741

1. 0
2. 6
3. 5.5
4. 0
5. 0
6. 5.9
7. 14.5
8. 0

I'm assuming you can at least bypass the whole effect with the foot switch?  That means the connectors and Jacks are OK.   It doesn't confirm the footswitch is OK.

Can you make sure the footswitch is switching the output jack to the 5uF cap + 47k resistor at the output of the unit?

Focusing on getting the clean signal working first.

When I check the DC (see below) it all adds up and there's no DC reason why there is no clean signal.

It's a weird circuit because the DC biasing starts at the Bias Trimpot,
then propagates through all stages to the output,
then the input opamp picks up its DC from the output opamp (!)

The thing about this design is it only takes one fault and it all collapses.

The DC voltage on the SAD1024 is a little lower than I expected (maybe 5V or 6V) but 4V is not a crazy value.

You could try tweaking the DC.  Take an accurate DC measurement at pin 1 of the 4558 and write it down so you can set it back later.  Then adjust the Bias trimpot to see if it comes back to life.   *However* at this point hold off on that.

Do you have an Audio Probe or an Oscilloscope?   If you do it is very easy to check the audio at the output of each stage and find where it stops.

http://geofex.com/FX_images/audioprb.gif
--------------------------------
DC around the loop starting at Bias Trimmer sets DC
Inputs first then outputs.

RC4558

2. 4.3
3. 3.9

1. 4.3

SAD1024A voltages

2. 4.3
15. 4.3

6. 6.4
12. 6.3

RC4558

5. 5.8
6. 6

7. 6

UA741
2. 6
3. 5.5

6. 5.9
--------------------------------

QuoteRegulator has 14.9v on the INPUT pin
Regulator has 22.1v on the OUTPUT pin.

Are you sure you are interpreting the pins correctly?
15V should be on the output.   

Check out the pic I posted before.
Also note you are viewing the PCB from the bottom *and* the pin-out extract from the data sheet is specified as viewed from the bottom of the device.

https://postimg.cc/image/qaj02loln/

Rob yes you are correct 14.9 output and 22.1v input.

Corrected my post.

I don't have an oscilloscope nor have I made an audio probe before or used one.

QuoteI don't have an oscilloscope nor have I made an audio probe before or used one.

The Audio Probe is a very simple idea.   It's a probe which lets you listen to the signal and various points in a circuit.   For example you can listen to the signal at the output of the first opamp in your circuit to know if the sound is getting through.   Then you listen to the signal on the second opamp etc.

The Audio Probe is just a capacitor with a wire (the probe) and a jack so you can connect the probe to an amplifier.   You listen with the amplifier you connect it to.  It can be you guitar amplifier - just turn it down!    Or preferably some crappy little amplifier like some old PC speakers.     I wouldn't use a HIFI amp and speakers as some faults can take out the tweeters.  The capacitor just stops any DC in the circuit feeding through to the amp.  It also stops the amplifier placing a DC load on the circuit you are testing.   

You should connect the ground side of the probe to your circuit.

Check it out,
http://geofex.com/FX_images/audioprb.gif

For a one-off job you don't need shielding unless the buzz annoys you.   Personally I'd make the probe out of some coax.

For the type of problem you have the audio probe is the absolute ideal tool.   Minutes to make and minutes to debug where the problem is.   It's a good "investment" - seriously!