1981 V6 (9V) Electric Mistress does everything but flange! Help request.

[tj7]

1981 V6 EH Electric Mistress.
http://www.metzgerralf.de/elekt/stom...tress-v6.shtml

I dug this pedal out this week, having last used it a few months ago. It's my spare.
I have done nothing to it since last using it, but inexplicably it's decided to stop flanging.
I have no idea why.

Bypass works fine.
The "filter" mode works (or whatever that other effect is, the metallic kind of effect).
Switch to flange and it stays in the same mode, so which ever position the switch is in, I only get that filter effect.

There are no strange noises in bypass or active mode.

I have tried using 9V battery as well as without battery and with direct power instead, and in isolation of other pedals.
Nothing makes any difference.

I have opened it up and checked for any broken solder / wire connections and can't find any.

Has anyone had a similar problem and / or have any ideas how I can solve this?

Thanks!

http://www.imagebam.com/image/c00f97439299378

http://www.imagebam.com/image/49fc11439299406

http://www.imagebam.com/image/11d14c439299443

[strassercaster]

just watched your video. wish i had seen it before my post. thats pretty amazing. i modified my phase 45 90 and small stone for univibe ha ha. i have a question if i wanted to mod my univibe for phase . What would be a good cap value(range) to start with? i pure
y guessing 47n?. i think the LDrs are so lish and warm i want to hear them phase ha ha. you guys are upto some serious stuff here. I love it. i wish i would have gotten into this years ago but i got the fever now. please explain a little about whats going on in the video. it sounded nice and chewy extra. warbled and to be honest like a univibe on steroids. the  androvibe steroidvibe  ha ha. killer vibe

[tj7]

just watched your video. wish i had seen it before my post. thats pretty amazing. i modified my phase 45 90 and small stone for univibe ha ha. i have a question if i wanted to mod my univibe for phase . What would be a good cap value(range) to start with? i pure
y guessing 47n?. i think the LDrs are so lish and warm i want to hear them phase ha ha. you guys are upto some serious stuff here. I love it. i wish i would have gotten into this years ago but i got the fever now. please explain a little about whats going on in the video. it sounded nice and chewy extra. warbled and to be honest like a univibe on steroids. the  androvibe steroidvibe  ha ha. killer vibe

Woah dude, I don't know how you managed it but you sure as heck haven't written a reply to *my* thread.... damn, got all excited thinking it was a solution! Please don't reply to this, as I'll only get another notification making me think someone has actually replied to my post.... thanks in advance.

[Fender3D]

Hi Tj,

I was going to mod my airplane into a helicopter when I saw your post which reminded me the crazy jet flanger effect....












lol

jocking... 

check the filter matrix switch first, otherwise focus on LFO (ic4a or ic4c).

[tj7]

check the filter matrix switch first, otherwise focus on LFO (ic4a or ic4c).

Ok, but check how...?

[DrAlx]

The "filter" mode works (or whatever that other effect is, the metallic kind of effect).
Switch to flange and it stays in the same mode, so which ever position the switch is in, I only get that filter effect.

You say Filter Matrix mode works but didn't clarify if that mode fully works.
When in FM mode, does the Range pot affect the sound?

You also say when you put it in Sweep mode, it sounds the same as FM mode.
So same question for that case.  Does range pot have an effect on the sound?
If it does that suggests it is stuck in a fully working FM mode, and that points to a bad switch.
If you find that range pot only has an effect in FM mode, but not in Sweep mode then that suggests non-functioning LFO.

The switch has 6 connections in this pattern...
   X  O  X
   X  O  X
Put the Range pot at maximum and the Rate pot to give slowest sweep, and then measure the voltages on the 4 X pins.
One of those pins will be connected to the LFO output and so have a voltage that varies in time.
When in "Sweep" mode, that pin with put its varying voltage onto one of the central O pins.
So if you don't see a varying voltage on any of the X pins, then then the LFO is not working.
If you find a varying voltage on one of the X pins but not the O pin, then the switch internals are bad, and switch-cleaning spray could fix it.

[Granny Gremlin]

Ok, but check how...?

Take an Ohm meter and make sure when you trip the switch it actually switches output contacts (remember, the contacts come in groups of 3 depending on if it's a single or double pole etc - the middle is in, and the other 2 are the out depending on switch position).  That's an old switch; they can go (especially if you used it a lot). Check for continuity between middle and both sides (only one should work); throw the switch the other way and check again; the other putput should work.  If either  both outs work or if the working out does not change with switch position then the problem is the switch.

... yeah what DrAlx said.

[tj7]

The "filter" mode works (or whatever that other effect is, the metallic kind of effect).
Switch to flange and it stays in the same mode, so which ever position the switch is in, I only get that filter effect.

You say Filter Matrix mode works but didn't clarify if that mode fully works.
When in FM mode, does the Range pot affect the sound?

You also say when you put it in Sweep mode, it sounds the same as FM mode.
So same question for that case.  Does range pot have an effect on the sound?
If it does that suggests it is stuck in a fully working FM mode, and that points to a bad switch.
If you find that range pot only has an effect in FM mode, but not in Sweep mode then that suggests non-functioning LFO.

The switch has 6 connections in this pattern...
   X  O  X
   X  O  X
Put the Range pot at maximum and the Rate pot to give slowest sweep, and then measure the voltages on the 4 X pins.
One of those pins will be connected to the LFO output and so have a voltage that varies in time.
When in "Sweep" mode, that pin with put its varying voltage onto one of the central O pins.
So if you don't see a varying voltage on any of the X pins, then then the LFO is not working.
If you find a varying voltage on one of the X pins but not the O pin, then the switch internals are bad, and switch-cleaning spray could fix it.

Thanks for all this info everyone.
I have never done more than basic soldering, so I am going to have to buy a meter and learn how to do these measurements!

However - I have more info.

In *either switch* position, neither RATE nor RANGE pots make any difference.  They do absolutely nothing.
The COLOR pot *does* affect the sound - the Filter sound is made deeper with a higher knob position.  This is the same in either switch position.  It's evidently stuck in filter mode, but given this new info, does this also mean the LFO has died?
If so, would it just make more sense for me to buy a replacement part and solder it in?

[DrAlx]

Range pot doing nothing means filter matrix mode is not actually working either.
At this point I'm not even sure you have a working BBD.

You say the color pot does something to the sound. Can you actually get "bell-like" sounds in FM mode when Color is set high ?
If so then the BBD may be OK, but for some reason is only ever being clocked at one clock rate.
If you can, record some sound samples and upload them to soundcloud or some other file sharing site so we can have a listen.

If the sounds are bell-like then the BBD is probably OK, and the problem is that it is only ever getting clocked at one rate.
No bell like sounds suggests broken BBD.

[Fender3D]

If the filter/matrix switch is broken ic4b can't work properly...
If you happen to have a dpdt switch, you might swap it just to see if it works.

Just remember you're dealing with an extremely rare and expensive SAD1024 here.
Before you make any further damages, consider referring to an authorized or capable technician

[tj7]

If the filter/matrix switch is broken ic4b can't work properly...
If you happen to have a dpdt switch, you might swap it just to see if it works.

Just remember you're dealing with an extremely rare and expensive SAD1024 here.
Before you make any further damages, consider referring to an authorized or capable technician

I'm in Australia.  Not gonna happen.   I'll record some samples tonight.
This is really inexplicable.  This pedal has been sitting in a box for two months after perfectly functioning at last use.... and suddenly this has happened.  Bugger!

[Granny Gremlin]

That's why I think it's the switch.  Similar thing happenned to me with a vintage bass' output jack the other month - I was worried because it has complex electronics (a large Moog circuitboard) and some irreplaceable parts, but I just needed to replace the extra long bushing Switchcraft jack and it's all good. Hadn't played it for a year or 3 and it was fine the last time I unplugged it; been in it's case ever since.

[tj7]

The "filter" mode works (or whatever that other effect is, the metallic kind of effect).
Switch to flange and it stays in the same mode, so which ever position the switch is in, I only get that filter effect.

You say Filter Matrix mode works but didn't clarify if that mode fully works.
When in FM mode, does the Range pot affect the sound?

Ok, here's a sound file:
https://soundcloud.com/matthew-h-slaughter/9v-ehx-em-color

This is EXACTLY what I get in either switch mode.  The variation in sound you hear is me changing the position of the COLOR pot.  The other pots do nothing....

[DrAlx]

It sounds like the BBD is fine, and the VCO (i.e. clock generator) is most probably OK too.  That's good news.
The problem must be that the control voltage for the VCO is never changing.
A bad switch (mentioned above) is the most likely culprit.

The switch pins look like this

1  2  3
4  5  6

One switch position will connect (1 to 2) and (4 to 5) like this:
1--2 3
4--5 6

Other switch position will connect (2 to 3) and (5 to 6) like this:
1 2--3
4 5--6

Slide the switch to sweep mode, and then take of couple of flat screwdriver blades (or knife blades) and make those connections manually.
e.g. if the switch is slid over to the left, then connect the 2 sets of pins to the left using the two blades
Otherwise the two right sets of pins.

There should be enough hiss on the pedal to hear any sort of sweeping, so you don't need to play the guitar with your feet while your holding the blades in place

[tj7]

Slide the switch to sweep mode, and then take of couple of flat screwdriver blades (or knife blades) and make those connections manually.
e.g. if the switch is slid over to the left, then connect the 2 sets of pins to the left using the two blades
Otherwise the two right sets of pins.

There should be enough hiss on the pedal to hear any sort of sweeping, so you don't need to play the guitar with your feet while your holding the blades in place

Ok.  Here's a photo of exactly what I did:

http://www.imagebam.com/image/ede8c0440055109

The audio file is a recording of me manually making the connection between the pins as pictured, also just 2 at a time eventually covering all permutations with the effect switch flipped left AND right.  As you can hear, it makes no difference which mode I have the pedal in. 

I have sat there gingerly manually connecting pins with this piece of metal for quite a while and at no point can I get any evidence of a sweeping sound or the flange effect that I am all too familiar with. I have also found that adjusting the RANGE and RATE knobs makes no difference to this process.   Sometimes, as you will hear, when I held the place between pins in a certain way the effect was bypassed altogether.

Thoughts?

https://soundcloud.com/matthew-h-slaughter/ehx-em-9v-switch

[PRR]

I believe your link to the project page was mangled in the copy/paste.

Page: http://www.metzgerralf.de/elekt/stomp/mistress/electric-mistress-v6.shtml
Schematic: http://www.metzgerralf.de/elekt/stomp/mistress/images/1981-electric-mistress-v6-schematic.gif

> does this also mean the LFO has died? ...make more sense for me to buy a replacement part...

LFO is at least 9 parts and 20 connections. Which one wants replacing?

DrAlx seems to know this circuit and his advice seems excellent. While there still could be some question about switch (AND connections), soon you need to meter voltages around the LFO, IC4a IC4C and associated parts. As a dumb-guess, IC4 pin 8 should be wobbling from +2V to +7V at a tremolo-like rate. (Many meters can't display this properly, but a "wobbly" reading suggests LFO action; a dead-steady reading is not good but a good clue.)

[tj7]

Thanks.  I have ordered a multimeter so I can do these tests....

[DrAlx]

Trying all sorts of different permutations will confuse things.  You should only connect the two pairs of pins on the switch.  e.g. if the switch is slid over to the left, then its the 4 left-most pins of the switch.  Also you need to be using use TWO blades, one for the top pair of pins and a separate blade for the bottom set of pins.  Did you do that? I'm not sure from your reply or photo.

I have a 9V EM clone, and I've put it in SWEEP mode.  I put the COLOR to maximum so I can hear the BBD clock noise as much as possible, and I can here the periodic change in noise as it is sweeping (I have Rate pot around 50% to 75%).  I don't play the guitar through, I just listen to the output noise of the circuit. When I go in with a blade and short out the relevant pins I get no change at all in the  noise.  In other words, you couldn't tell I was messing about with the circuit at all ('cos my switch is fine).
In other words, if the switch was doing its job and connecting Pins 1 to Pin2 (for example) then sticking a blade between pins 1 and 2 would not have any effect.

Now from the sample it sounds like sticking the blade in there WAS doing something.  See where I put a comment on the soundcloud clip.  There are "record scratching" type sounds.   That's due to the control voltage for the BBD changing (going from high to low very quickly when it "scratches up").
Unfortunately because you haven't said exactly what pins you were shorting out, and that you tried all sorts of combinations, I can't tell if these sounds occurred for the pins of interest, or for some other combination that is not relevant.
Do the test in SWEEP mode only, RANGE and COLOR at maximum, RATE over 75%.  Connect ONLY the two pairs of pins I described.  Try with one blade connecting the top pair only, then with one blade connecting the bottom pair only, then with two blades together (one for each pair).  If you hear a change in the output noise then the switch is not good. If you find that the noise does not change at all, then the switch may be OK, and the problem could be with the LFO section.

A meter will help greatly.

[tj7]

Trying all sorts of different permutations will confuse things.  You should only connect the two pairs of pins on the switch.  e.g. if the switch is slid over to the left, then its the 4 left-most pins of the switch.  Also you need to be using use TWO blades, one for the top pair of pins and a separate blade for the bottom set of pins.  Did you do that? I'm not sure from your reply or photo.

Thanks for all your help here.

https://soundcloud.com/matthew-h-slaughter/ehx-em-9v-switch-2

I had the box in "sweep" mode, and used two metal conductors (a bread knife and the back end of a scalpel) to connect the pins as you suggested, i.e. the 4 pins on the same side as the switch position, top two and bottom two each connected).  FYI I found exactly the same response when I tried the other two pins on the opposite side of the switch position, but didn't record this.

I would have thought that if I managed to get a stable connection, I'd hear a proper flange effect, even momentarily?

[DrAlx]

Very strange.  The blades are doing something 'cos I can hear the BBD clock noise disappear, but it is not flanging.  So there's more going on here than a bad switch.  We'll have to wait for you to post meter readings.

We'll need the voltage on all pins of the LM324.  Pin 8 should have a voltage that varies over a range of a few volts, and you should see this voltage going up and down when you put the RATE to low.

After going through the switch (in FLANGE mode) that varying voltage gets scaled and appears at Pin1 of the LM324.  So if the RANGE put to maximum, then you'll see a varying voltage at Pin1 of the LM324 also.

That voltage then gets passed to Pin2 of the LM311 IC (which controls the speed of the BBD clock).  So if you don't get flanging, then its likely that one of the voltages described above is not changing.