electric mistress help !! (please) SOLVED !!

[Pierre]

hi !!
it seems that im only posting problems 
I just finished GGG's Electric Mistress and no surprise, it's not working...Im only getting hum and a subtle signal with some flange effect, no matter what i do with the trims, the hum its allways present. I suspect that the problem its in the power supply...Im using a 9v-0-9v transformer, that's giving 19V, but the 15V regulator's output reads only 11V...
For the rest, everything seems to be OK, all resistors /caps values are correct, all ic's are well oriented, the only thing is that i could not find a TL071 and i put a TL072 instead...
Any help will be appreciate...thank you !!!!

[markusw]

You realise that the TL072 is a dual opamp while the TL071 is a single opamp, thus they have completely different pinout ?? Also there is no TL071 in the schem?

Markus

[Pierre]

wow ! thanks !!!
Stupid me  ...i build it just with GGG's loyaut, not paying attention to the schematic...IC 1 in the schem is a 741 and in the loyaut  its marked as a TL071...
Now its working, but im not shure if it's soundig as it should...a never played with one so i cant tell, but it does not sound like a flanger, it's a weird effect, cant decribe it...and it is a bit noisy...i dont know, maybe i did not set the trims correctly or there's still something wrong...

[Pierre]

i was playing a little more with the trims and im starting to find some cool sounds, even more putting a distortion in front of it...but it seems that the "rate" pot goes from very fast to too much...is the any mod to slower the effect down? 
and one more thing...i have found that the "balance" trim does not do allmost anything...is it normal?

thank you !

[Pierre]

ok...maybe the problem of this wierd behavior is the power supply, or in the 15V regulator...it seems that i did not pay attention and i put a 7815 instead of 7815 AC ...i dont know how bad it is but, since i dont have another voltage reg. i was wondering if i can try powering it with a 18V regulated power supply instead of the 18V AC transf...Can it be powered with 18V DC ?...can i leave the input diodes?..
...sorry for those silly questions but after 2 years of DIY im still newbie

[Pierre]

...well, now im powering it with a 18V regulated power supply (the same of the PT-80), i tought that it wont work because the proyect indicates an AC power supply, but it works and the allmost without hum and noise...
The only thing that keeps bothering me is the speed of the effect, it goes from fast to very fast and at the end of the rate pot the effect is more like a strange kind of reverberating sound...Again, i have never had the chance to try an original Electric Mistress so i dont know if this is normal...but with my clone i dont think that i have i wide range of usable sounds...With both rate  and range pots at cero, it sounds like a crazy chorus...increasing range and rate, it sounds like...i dont now, like some kind of an alien spaceship alarm system...
Again, any help will be very usefull !
Thank you

[markusw]

Probably check again everything around the LFO (IC4a,b,c), maybe also for solder bridges, shorts....
If you get some chorus effect your'e at least not that far away from having it working

Markus

[Pierre]

im checking all again, resistors, caps, looking for solder bridges and i cant find anything wrong...I guess its not some chorus that i get, im getting flange sounds, evrything seems to work ok, the filter matrix switch do what i think it must do...the only problem its the speed...the effect goes much more faster than the sound samples i heard in Tone Frenzy...
and other thing, the balance trim pot does not do anything...
I allready changed pots (just in case) and the .22µf cap and the 33µf tant. caps are correctly oriented...

[GibsonGM]

I'd suspect that my rate pot was the wrong value...maybe you have linear where you should have log?  Putting a resistor across the outer lugs will put the pot in parallel, to decrease its value (R1xR2/R1+R2, you get 1/2 if they're the same value).  Or putting a R in series will raise it (R1+R2).  I've had the same problem, due to not having the correct pot, and fixed things that way til I could get the right pot (see "The secret life of pots" on Geo's page).   What is making me think your pot is off is that you have fast chorus on minimum setting, and wild & crazy above that.  So, the min is probably maxed, see?    Good luck! 

Sounds like a cool effetct.  I'm going to make one too, and you can probably help me out then! 

[Pierre]

that's the first thing i've checked, but no, its a 1M log pot (Alpha) as indicated in GGG's  schem...i messured it with the multimeter and it works ok...

[Pierre]

ok...i give up !
everything seems to be ok and i dont know where else to look...minimun speed is way to fast and there's  nothing i can do to solve it. Maybe one of the ics
is not working properly...(hope its not the SAD1024 )...

[markusw]

ok...i give up !
everything seems to be ok and i dont know where else to look...minimun speed is way to fast and there's nothing i can do to solve it. Maybe one of the ics
is not working properly...(hope its not the SAD1024 )...

Maybe the two 33µ tantals in the LFO are the wrong value or damaged? btw, the LFO will work (or not) regardless whether the SAD1024 is present or not. So I don't think it's the SAD1024.

.... it would be helpful if you'd post voltages at the IC pins.

Markus

[Pierre]

i cant say if they are damaged, but the 33µF tant. values are correct, and well oriented...
The voltage at the IC 4 pins are :

1- 6.60V           8- 6.59V
2- 6.59V           9- 6.61V
3- 6.59V          10- 6.59V
4- 14.49V        11- 0 V
5- 2.36V          12- 1.70V
6- 2.40V          13- 1.70V
7- 3.56V          14- 6.59V

I messured them powering the effect with a 18V regulated PS and with rate por set at full ( 0 Ohm)...Maybe this is a stupid comment but if i set the rate por at minimum (1M) i cant have a stable read in some IC's pins...
Thanks (i feel less alone)

[gez]

.... it would be helpful if you'd post voltages at the IC pins.

It would be even more helpful if you posted a link to the schematic.  I've just spent a few mins trying to find it at that site and had no luck.  Can't say I'll be able to help, but plenty of people here probably can...if you link to the schematic [/hint]

[Pierre]

here it is...
http://www.generalguitargadgets.com/diagrams/dmistsc.gif

[Pierre]

well, now im shure that the effect in it self works as it should. I remouved the 1M log "rate" pot just to change it for another. I messured it and, again, it seems to work ok...but, just in case, i replaced it with another without any luck. But, thats what i've observed, leaving just the wires of the pot conected to the PCB, and toching them i have a very nice flange effect, from really slow to fast, depending on how firmly i hold them...i dont know what is the resistance of a human body (if this has any sense ) but with that value i have a perfect flanger...
Sorry if this post and all the topic is a bit silly but i would like to have this wondefull (and expensive) flanger working...

[gez]

Check the values of C13 and C14 and check their orientation.  While you're at it, double check the values of R25, 26, 27 & 28.  Also, scrape between the traces of (and near to) your rate pot with a scalpel.

I've never built one of these, so don't know how slow the sweep is supposed to be, but it sounds as though your effect isn't working as intended.  If you do have the right values in etc (and please try all the above first) it's a trivial affair to lower the range; making R28 larger, or increase the values of C13 and C14 is probably the easiest approach.

This is a flanger, not a chorus.  The fact that you're getting reverb sounds suggests you're running the clock too slow.  The 'clock adjust' trim should sort this out...that's what it's there for.

[Pierre]

 
i finally removed C13 and C14. Not that they where the wrong value but it was my last chance...I put two 47µf electrolitics in place (i did not have any 33) and to my surprise, it works !!!...Now i have a very nice flange effect, very very slow (maybe too slow, but i'll change caps to 33µf again)...So i guess one of them was damaged, it never happend before but there's allways a firts time...
Thank's Gez, Markusw and GibsonGM, you just pointed where i should look 

...and thanks for your patience, i know my english is maybe a little hard to read....

[GibsonGM]

Glad it worked, pierre!  Just another example of checking, double and triple checking, and playing around in the most likely spot for the problem to be    Could've been a bad solder joint which got fixed when you replaced the caps...but that was the right way to approach it!     

You like the Electric Mistress? The last one I built was the Easy Vibe, which I really like for vibrato - would like more flange, so I might build the EM.  Is it really deep?

[Pierre]

untill now it was pretty happy with my FL301 clone (from Tonepad) but i like this one a lot more (maybe im goinig to try them toghether  )...I dont really know how i real Electric Mistress sounds, but it does not matter, this one sounds good. Maybe i have to do some adjustments, like replace the caps for 33µf and playing a little with the trims (the balance trim stills doing nothing )...