3 Leg Dog problems

[Michael Allen]

I threw together another one of these and I'm getting some crazy problems. I can play through it for awhile but then all sound cuts out and this crazy siren starts at a low freq and gets higher and higher and then oscillates at the top of it's frequency range. When I cut power and restore it, it works again with the same problem. Sometimes it's longer and sometimes it's right away.

I've replaced all caps and put a 100u across the power rails. No success. Any ideas?

[Connoisseur of Distortion]

the chip is very picky. I had a CD4049UBCN that didn't work, but a CD4049UBE will. what model are you using?

[Michael Allen]

UBE

[Ge_Whiz]

Have you:

1. Used a fresh battery?

2. Been sure to ground any unused inverter inputs?

3. Noted ROG's comments on the layout of this very-high-gain circuit? If you have built on veroboard, cut and isolate any unused track sections to reduce stray capacitance. If you have used perfboard, ensure that all wires are as short as possible.

4. Checked to see if the chip gets hot?

[Paul Marossy]

Yeah, a new 9V battery is imperative. That thing will squeal like a pig going to the slaughter on a low battery! BTW, I built mine exactly per the runoffgroove layout.

[Michael Allen]

I built this one using the pcb layout from runoffgroove to compare with my layout on Loudnoise. Had some noise and wanted to see if it was the layout. I'm using a power supply that's pretty steady .....

I don't think the wiring should be a problem since when this siren goes off, it's all sound cut out except for that siren. I've had pther oscilation problems before but this doens't sound like them.... it's weird man

[Paul Marossy]

That is weird. I hope you get it figured out.  :?

[soggybag]

I built a tube sound fuzz (almost the same as the Three Legged Dog) on a bread board the other day and it wouldn't stop oscillating. I tried a few things couldn't get it to stop. So I took it apart and figured I come back to it later.

[jmusser]

I must be really lucky, because I've never had any of these problem, with circuit oscillations building on perf board. I rarely get any type of a circuit squeal without the circuit even being boxed! I used the UBE chip on that one, and it worked like a charm. I hope you get it figured out, because it's the best thing that ever happened to my solid state amp.

[gez]

It might be misbiased, which could account for part of your problem.  Would help if you posted voltages and linked to a schematic...

PS  You did tie all gates of unused inverters to one or other of the rails didn't you?

[Michael Allen]

yeah, unsused inverters to ground. I'll post voltages later today

[Michael Allen]

seems that the problem was with my power supply. Homemade and it must have some kinks in it somewhere....

works fine now. When i turn down Tone knobs (and volume but not as bad) the static and noise increases unbearably,,,, is this normal? how can I fix it.. I've shielded in and out so is it just more wiring problems?

[gez]

seems that the problem was with my power supply. Homemade and it must have some kinks in it somewhere....

works fine now. When i turn down Tone knobs (and volume but not as bad) the static and noise increases unbearably,,,, is this normal? how can I fix it.. I've shielded in and out so is it just more wiring problems?

Is this 'boxed' or on a breadboard?  Often noise will be worse when a circuit is on a breadboard.  

Try it with a battery to see if this improves matters.  If so, then you still have some work to do on your PSU.  

With any high-gain effect noise is going to be more noticeable when you back off volume, these circuits tend to be reasonably quiet though.