Cooked a schumann pll clone while tuning in voltage.Where to start trbleshting?

[Bandwagonesque]

Hi everyone. With great frustration, I tonight cooked a recently finished schumann pll clone upon trying to tune the voltage section in. I seemed to have arced my probe across some point that it didn't like. I am going off of my own layout but here is the schematic. I really am at a loss to be quite honest. Before I light my head on fire, can someone tell me where one would start troubleshooting this circuit? It passes signal, but acts very erratically and seems to only work when the trigger is at noon. have zero idea what I need to replace now to get it back to the normal somewhat working (definitely worked way better right off the bat but obviously needed to be tuned in).  Just to let everyone know, i've actually jumped the gun and replaced the voltage regulators and chips already to no avail. . Everything else seems to just be diodes and passives. Do I need to begin replacing these too? Thanks for any help anyone can give and take care.

[PMowdes]

You need to make sure that you don't install the ICs until after you have tuned the power, some.of them won't tolerate higher voltages. 

[anotherjim]

Whatever, a 74HC14 won't live long supplied by 12V will it? Absolute max supply of 7v for those. Surely a CD40106 for that job?
But yeh, don't try switching on with chips in until setting the voltage regulators.
Trimmer pots can't handle much power, you might have burnt the track on one. A short would have to exceed around 1A to damage anything else.

[PRR]

Why would it need to be "tuned-in"? It wants a stable supply, not too big, not too small, and not toooo asymmetric.

And why 10k pot?? That allows dialing-in 105 Volts. (Or actually 89% of the pot rotation is useless, the last 11% hyper-sensitive, which is sure to confound the builder.)

[Bandwagonesque]

I really wish I knew the technical side to explain why but it really seems like a head scratcher of a circuit. here is what I based my layout on. I see zero wrong with my layout and it did work. I've built one before that I had to tune in and it really got it close to sounding like a real one I had access to. without tuning things into -12 +12v there it reacts real sluggish. but I tried replacing both the voltage regulators and pots tonight and pulled the ic's before tuning and it seems the voltage section is around 17v on both sides. I cant get the trim pots to adjust a thing.

I'm about to post my ic voltages and have a clone to compare it to post correct ones. I really don't know where to go from there. But there are diodes and electrolytics and film caps and resistors I have yet to replace to see where the culprit may be. I hate to chase my tail but can anyone tell me that if I need to keep replacing things and which components would make the most sense first to replace from here (voltage regulators and those trim pots have been replaced.) and if i measure voltages am I wanting the IC's in circuit? thanks alot everyone and take care. wish I didn't screw up this stupidly on this.

[antonis]

I tried replacing both the voltage regulators and pots tonight and pulled the ic's before tuning and it seems the voltage section is around 17v on both sides. I cant get the trim pots to adjust a thing.

Check R1 & R2 values..

P.S.
AS Paul already said, you don't need high value trimmers..
(actually, you don't need trimmers at all..!!)

You can estimate TRIM value from the formula: (V+) + 0.7(*) = 1.25 X [ 1 + (TRIM / R1)]
(*) D3 forward voltage drop..

[Bandwagonesque]

hi and thanks a bunch for every ones help so far.

thanks antonis for the help. I did replace r1 and r2 (240r and 120r iirc) and that didn't seen to make a difference either. so so far i've replaced

the voltage regulators, trim potentiometers (which I will go about replacing with resistors once I can order some more resistors now that I have the formula, thx again). and those resistors to no avail. Should I go about replacing the 470uf power caps or diodes?

hope i'm not a bother but this is one of my great regrets. stupidly measured across the bottom of the board to just beg for a bad arc which is what happened. Don't know why I didn't measure off the pins of the lf347n sockets. But glad I made the happy mistake of having the chips in when I turned it on. It works in that regard. It sounded about 70% there with all pots and switches working, just needed that last bit to really get it there. I can't explain why but I have a clone which was tuned right next to an original. That working clone of mine is about 90% there to the original even when at 12v - or + in the power section. This one I cooked wasn't equal to either but I reckon it could get there had I not cooked it.

I guess the tell tale sign is how the trigger and preamp work. on the schumann, iirc the trigger was at midnight it would self oscillate and go nuts. if it wasn't tuned right it was real sluggish. once it was tuned, every clone I made reacted the same if maybe sounding a bit different. can't explain it though.

[Bandwagonesque]

Hi everyone and hate to bump this post. I'm still running into a good amount of trouble with my PLL after cooking it. I went the lonnnnnng way around tonight and all at once, replaced basically everything at once except the pots. the power section, everything replaced with fresh components. I tested all of them and none of them seem to test 'damaged'. I'm really at a loss as I still am measuring at 17V volts on the + and - sides of the power section and can't get even the new trims to react at all or tune down to 17V.

This seems to be the stupidest mistake ive made so far in my building in that ive been chasing my tail to no avail. Can anyone tell me why it would still measure at 17V or kind of how this circuit works in a nutshell as I really am too green at this point to figure anymore out. The info so far given makes great sense, thats where I fried it right around the voltage regulators but even after replacing all of that i'm still stuck banging my head.

can anyone with good experience with the PLL tell me what may be wrong? I almost feel like I have to rebuild the thing entirely, like a friend the perfboard itself i'm going that crazy now. Would be happy to provide other voltages too, I don't have the IC's plugged in of course. I figure once the power section is fixed and I can tune it in I can plug them in and be back on my way again. Any help would be so so so appreciated as I truly miss this thing. Seriously the stupidest flub that i'm paying for dearly in time.

[antonis]

Maybe trimmer wipers aren't connected on respective ADJ pins..

[duck_arse]

might we see some photos of what you have built, please?

[antonis]

might we see some photos of what you have built, please?

You have to admit you're quite a curious/nosy/snoopy/busybody guy, aren't you Stephen.. ?? 

[anotherjim]

That layout looks like it's for TO-92 plastic case regulators. Schematic names the bigger TO-220 tab case. What did you fit? In my experience, no apparent regulation happens when the regulator pins are wrong way round and I think the choice of case reads backwards on the pinouts.

[11-90-an]

might we see some photos of what you have built, please?

You have to admit you're quite a curious/nosy/snoopy/busybody guy, aren't you Stephen.. ?? 

I mean, it *is* protocol around here, right? 

[Bandwagonesque]

hi everyone and thanks a bunch for the replies.

unfortunately i'm between a rock and a hard place as my pll clone's layout is unlike anything out there, in that I can stick a layout up to use as a reference. And this build...oh boy. I may need to yank the guts to get a clear topology shot. I'll provide photos here real soon but afraid they may only go so far in helping.

I may have to trace this or the topology at least so it may be a couple days. But I will say that I replaced all the components wit the same type I originally used that I accidentally cooked (from the same batch). Now this PLL clone looks like it has some nominal differences in comparison to the vero layout thats up that everyone seems to build from. So once I can get a trace of at least the circuit with the power section up I'd be happy to share it in hopes something turns up. But I did replace both of them in the same orientation as the original and still having my issues. I'll make a list of the differences in components used as there are differences. But i'm just stunned how its still not working after replacing them with the exact same components from the same batch.  *shakes head*

I know it sounds crazy, but if say I drank enough and wanted to swap everything out again, would I have to replace the pots too? Apologize for asking crazy questions here as i'm still at a loss. But thanks for all your help so far folks, it means a whole lot.