EH electric mistress

[OG]

I am trying to debug an EH electric mistress ( the standard version from +-1980). I have two pcb , some wires are missing but with the schematics i think i have enough information about the wiring.
I read that early El Mistresss  had some common problems with their voltage regulation and that Electro Harmonix published a note explaining how to solve this by changing parts. Does anyone knows about this?
Thanks for helping me if you can.
OG
Ps :  from what i remember, back then the El Mis and some other EH products were so unreliable that salesmen in the Brussels' music shops were giving you a "from the counter to the door waranty".
Great sound anyway so it's worth trying to improve it.
OG

[StephenGiles]

I have this note at home, so I'll upload it when I can. Personally, I don't think there is much you can do to "improve" the Standard Electric Mistress. It is stripped to the bone already so any "improvements" are likely to mess up the sound. For instance if you try to improve the almost non existent filtering, you will lose some of the bite of the beast. It may be worth buffering the 4013 - what do you think Mike Irwin?
Stephen

[Arno van der Heijden]

My Electric Mistress ticks like a clock, so you may have to look for improvements in that direction.

Stephen,
How good is your understanding of the original Mistress LFO? My Mistress sounds great on the faster settings, but the LFO has a weird asymmetrical sweep which hampers slower settings...
It can be heard on this sample:

http://www.student.tue.nl/T/A.C.v.d.Heijden/Mistress.wav (1.26mb)

I was suggested that this could be caused by the string of transistors on the base of the 2n5087, but these seems to have the right values. The Mistress didn't work when I bought it and I had to replace the SAD1024 and some opamps because they were fried, but I didn't replace the 4014 or the 339 so maybe it has something to do with that?

BTW, do you know how I can get a slight increase in volume (needed after a true bypass conversion)?

[StephenGiles]

I would change the 339 and 4013 as a first step, just in case something is amiss there. I'm still looking for the voltage regulation note - several thousand sheets of paper to plough through!
Stephen

[StephenGiles]

See here:
http://img.photobucket.com/albums/v317/StephenGiles/EHelectricmistress_UK.jpg
The note states:

Replace the 2N5087 or BC309 with a 2N4354

Replace the 2N3563 at pin 2 of the 741 with a 6.8v zener diode (1N5235B or equivalent)

Replace the transistor or zener at pin 6 of the 741 with a 47k resistor

Replace the 18k resistor at pin 3 of the 741 with a 22k

The recommended output voltage (on the collector of the PNP transistor) is 13.0v although the range 12.0 to 13.5v is acceptable
Stephen

[zeta55]

Hi.
I also have one that I had to replace the sad1024 chip and the 741 in. My problem is the "svosching" sound the cuircit gives. Should it be that loud. The flanging effect is great but the svosch is anoying. I've played with the two trimpots it does not filter the anoying sound away.

[OG]

Thanks Stephen.
The E M i'm trying to fix is actualy the one with the right parts/value as mentionned on the note. The other board i own is older then, corresponding to the other schematic one can find on several diy sites (geo, etc).
So unfortunately the  answer won't come from this note and  this doesn't tell me why it is so unreliable . I'll try to do the audio probe test and check the voltage, replace caps, etc...
By the way, there have been several post here and on ampage about "deticking" a delay line, and also about the sad 1024 which i wouldn't not replace first because generaly it doesn't seem to be the problem (there are posts by Mark hammer on these subjects).  Mine seems to work , tweaking the tripot i can hear the sweep going up and down. But the circuit is only producing a huge hum noise as if there was no ground, and there is no the signal going through even in bypass mode, which in this case is not a "suck" bypass type like on the first schematic but is taken after the 4558.

[Arno van der Heijden]

I would change the 339 and 4013 as a first step, just in case something is amiss there.

Ok, I'm gonna try that this weekend. I'll post back after that.

My Mistress is older than the one on the schematic you posted. It doesn't have all the bypass caps, so I might have to add them to get rid of the ticking sound.

BTW, does anybody know how I can make the Mistress a little louder?

[StephenGiles]

As to the ticking, I have a vague recollection that a 2200uf capacitor soldered accross the power supply did the trick, but switch off first.
Stephen.

Make it louder.......why?
Stephen

[Arno van der Heijden]

I made it true bypass...

[Arno van der Heijden]

Stephen, I put in new a 4013 and 339, but that didn't help....

I should note that I have never heard another Electric Mistress, so I don't know exactly how it should sound. Can you confirm that my sound sample doesn't sound like it should? I get this sound with max. feedback and min. range.

Any other suggestions? Could it be the 2,2uF NP?

[Johnny Guitar]

I have been thinking of buying a PCB of the Dlx Elec Mist from GGG. I have an old SAD IC which I've been looking to put in a project. The only flangers I have are an MXR (which I really like) and an Arion (which I don't like that much).

Is this a good effect? I realize it would be a tough project but would it be worth while?

Thanks,
John B.

[Arno van der Heijden]

bump