Microsynth troubleshoot! (Filter Question)

[j.frad]

HI everyone!
I've finally gotten to complete my microsynth and I'm at the trouble shooting stage...
I've reposted the project files here: http://rustingwall.free.fr/m/
beacuse I didn't want to spend too much time finding the old url again, if it's a problem I can remove it.

So here is the problem:
1)The regulators of the power supply get pretty hot, I don't know if it's ok (ggg bipolar power supply), the ICs all get the righ voltages...
2)The filter doesn't sweep.

I've probed the circuit and I cant get the sqare wave signal and the octave up signal ok, the gruitar signal is distorted depending on the gain, and the sub octave is kind of weak but that might be becaus I'm probing on a little 2W amp and using a bass guitar...

The overall signal (mix of all) gets to the filter, i get it at pin 6 of IC 10/11/12 filtered differently but the filtering is fixed
The attack delay seem to be sort of working.
The peak follower works, the voltage is higher or lower depending on my attack and on the gain, but I think it's a negative voltage, anyway it works...

The issue is in the stop detector, the small signal detector and maybe in the sweep generator of the filter (start stop frequencies' area).
-Point 6 which shouldbe high on silence is negative voltage and acts as a stop detector (goes "low", actually high because it is negative voltage at the end of the note)
-point 7 which should be at -8V and pulse high on, attack, is around 6 volts and goes lower on attack, it becomes negative if I turn the trigger pot butthen stays around  -8 volts and doesn't react to the attack.
-Pin1 of IC 7 which should be low and pulse high at the end of note (stop detector) is at around -8V and goes back towards 0V when I attack but doesn't really pulse.

It looks like things are mixed up between the three:Pin 1 of IC 7/ point7 / point6.
So this is what I tried:
on board number 3
-take out the jumper that comes from pin 1 of IC7 and wire that to point 7 on the board 2
-take out the wire that comes from point6 and goes to board 2, wire on board 3 where pin 1 of IC7 used to be
-take out the wire that comes frome point 7 on board 3 and wire it to point 6 on board 2.
this was supposed to "unmix" things. the start and stop frequency controls seem to gain some activity, bu all I get is still a distorted sound fith some high pitch filtering and oscillation...the squelch control is wierd, so is the trigger pot...
Not very useful...the filter sill doesn't sweep

Any suggestions? Does anyone remember having to do serious modifications? I did all the parts replacements needed...
thanks a lot!

[Sir H C]

The heat in the regulators means something else is probably getting hot too.  Check the op-amps, resistors, and caps to see if there is a short or relative short somewhere.  That would be the first step.  I don't think the regulators should get too hot (how many seconds can you hold them?)

[j.frad]

Well at first there was a short that I solved, now I can leave the power on for about a minute before it gets too hot...

[Sir H C]

Still those regulators should be able to take about an amp before they get really hot (without a heatsink unless you are dropping a lot of voltage across them).  Might just be good to feel the parts to see if anything is hot.

[j.frad]

and a good idea it was, IC3 is getting hot too...gotta find were the problem is...
might as well solve my other main problem: the sound of it!

[swt]

What type of ps are you using?. if you use the original ps, it's normal to be hot. If you use a bipolar with the 78xx series, remember you need +8/-10 volts for the circuit to work properly. What layout did you used?. let me know, and i'll se if i can help...

[j.frad]

well I didn't know about the +8/-10, that might be my problem, I still have IC3 heating up and it's not the IC that's fried because putting another one in gives the same result...
My power supply is the -9/+9 from GGG:http://www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf
I think I did pcbs for the original PS, I could try that next week...

Do you think this could cause such a horrible sound? all i get is distortion really...
My problem with IC3 could also cause the bad behaviour of the stop detector/attack detector/small signal detector sector of the circuit, but I don't know what would be the proble, the C12 tantalum cap seems oriented well...
Oh I had to sub the 6.8V zenners for 5.1V could this be a big issue concerning the filter?

Thanks for taking the time to help me, I'm really excited about this thing.

[Sir H C]

If that op-amp is going into current limiting from the excess current it is sourcing/sinking then yes it could well make things sound horrid.  Do you have the schematic as well as the board layout?  I am trying to see what IC3 is doing.

[j.frad]

sure, I just uploaded them here: http://rustingwall.free.fr/m/
IC3 is just after a low pass filter and get the signal to what controls the opening of the VCF and VCA if i can compare this to an analog modular synth so I guess a malfunction of this IC could make the whole thing go really bad, but I cant see the problem! I don't know what causes an opamp to go into current limiting...

[Sir H C]

Measure the voltages on all 8 pins of that op-amp.  That should give us the clues we need.

[j.frad]

ok! my voltmeter is no very accurate, I can't find the digital one anymore...
pin1:-9.5v to +9v depending on squelch pot
pin2:-0.1v changes if I turn the squelch pot, goes from -0.1 to 1.5 volts (approx.)
pin3:0v
pin4:-9.5v
pin5:0v
pin6:0v
pin7:1v
pin8:9v
I find it strange that the voltages on pin1 and 2 can go up to 9 volts with a 3.3Mega ohm resistor in series, is that normal?

[Sir H C]

Is R15 3.3 Meg (orange orange green) and R16 27k (red violet orange)?  It seems that the squealch is doing way too much as it should only get pin 1 moving a small fraction of the rail supply as the 3.3M and 27k resistive divider (with pin 2 staying at ground as an op-amp should have it) should make it really want to go about 1 volt.

[j.frad]

The resistor values are correct, the squelch was originally an internat trim pot, not ment to be moved.
My multimeter I strange, the squelch pot now only has a range of +/-2volts, anyway, it set the squelch so that pic2 is a ground, pin 1 is now at about +1 volts, but it is still heating...
it's midnight here, gotta get some sleep, i'll be back in 10 hours

[Sir H C]

All those voltages make sense now.  I can only guess that maybe the C7 capacitor is bad and shorting to ground.  With pin 7 set to as near 0 volts as possible does the IC still heat up?  Might have oscillations in there too.

[RaceDriver205]

Excellent! Ive nearly got mine finished too. Ive only noticed one layout error so far, and thats that R105 is repeated on board 1 and 2. So you should only need the one on board 1 installed, and the other left out.
Keep in mind that it is complicated as hell, so going over every section of board and checking that theres no shorts/wrong parts/missing tracks/bad polarities, may be necessary. I wrote all of my part values on the layout sheet prior to starting, and that will one of the first things ill check if it goes wrong.
I am using CA3080s coz CA3094s are crazy money, so I have to make an adapter board for each CA3094 socket.
Hope you get yours to work, then I know mine will work! 

[j.frad]

I hope yours will work! The IC still heats up with the right voltage, I'll try replacing the capacitor...
I also have to try using a +8/-10 power supply, might help  the sound...
I'm using all CA3094, it is a lot of money put in that project, I'd be sad if it wouldn't work.
What if I reversed polarity of C6, just before the square wave shaper, could that be a problem with IC3?

I've been checking this monster board so many times...If you run into trouble, race driver, make sure you tell us ok? I'm not sure I'll be done with mine...

edit: nevermind C6

[j.frad]

ok I kept probing the unit, R96 was no good, replaced it, now i get sound: very distorted (should the gain pot make it so distorted?), but i get different sounds with the voicing pots, the VCA works ok, depending on my trigger setting and on a fine adjustment of the squelchn the filter does have some effect but doesn't sweep , I noticed IC13 is heating...
IC3 is still heating but not much...

I subbed the 6.8v zeners for 5.1v, is that an issue here?

[j.frad]

funny thing, these two ICs are the only ones with jumpers underneath them...

[RaceDriver205]

Did you check R105 wasn't repeated?

[j.frad]

This is something I have to fix too,
I read that on a real unit r105 was 10k+1k in series, but the way I put them is in parallel, one in each space marked R105...
I'll fix that and keep you up to date... Is it critical? I guess so, I'm not really sure of the effect on the behavior...