PWM and 4066 troubles

[Radamus]

I recently breadboarded the PWM (from http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html ) After some initial trouble from misunderstanding my breadboard, I got it to work really well and I was generally pleased with the sound. I decided to solder it today and I finished everything. The way I did it was a little unusual, I think, because I used a DPDT as a control for a 4066 that actually switched the sound. Here's the problem: I probed the unit and I get a hum right off the bat from the input jack. No guitar sound, just a single tone humming. I disconnect the power, and the guitar sound comes through clearly. Power back on, it just hums. I plugged it into the output jack just to check, and it works just fine with the power in. Something is canceling my guitar tone and replacing it with some sort of hum, which occasionally comes out as the pulse wave.

I am assuming this problem is coming from the 4066 chip, but I don't know. Can anyone help me out with this?

I don't have any 9 volts, so I'm using an adapter that uses 13. I used this on the breadboard, too. I'm giving the control sections of the 4066 the full 13 volts, as with the Vdd itself.

I'm kind of winging it here. I don't know much about how the 4066 is supposed to work other than which parts connect and its total tolerance. The question, then, is: What's causing the hum?

Thanks

[Radamus]

I don't know if I was clear enough about the problem, so I'll try again.

I started probing this project right at the beginning, the input stereo jack, and I found that none of the guitar signal was present. Instead, it was a single tone hum. As I went through the circuit, this hum was modified and changed, but none of the guitar signal made it. I'm really not sure why the guitar signal stopped there. I tested the jack and it is okay. The only new thing to this project since I successfully breadboarded it is the 4066 chip. I followed the manufacturer sheet as far as I know. There are three IC's (I've never used any before) and I'm not sure which one might cause a hum or noise canceling. Is this something that is common? Will the schmitt trigger do it if improperly used? Have I fried a component?

I find this to be really bizarre and I don't know where to start diagnosing. Usually, I probe it until I lose sound or until something goes wrong, but this is wrong right at the beginning, which leaves me little to test.

Any thoughts?

[Paul Perry (Frostwave)]

The 386 might be oscillating. They are (in my experience) prone to this, if there are stray loose or long wires attached.
I haven't built this particular circuit - I try not to get involved if i see a 386 - but it has happened to me elsewhere.
If I were troubleshooting, the first thing I would do, is see whether the 386 is acting as an amplifier.

[stm]

To me it seems like the power adapter is the culprit.  You *need* to try with a 9V battery (a 12V battery would be OK).

[nordine]

Q1- Are you using a 4066 or a 40106? ..the schematic calls for the second, and yes they are different
Q2-You say 3 IC's, are you sure?.. the schematic has only 2, a 386 and 40106

i've fried lm386's before, also i've fried 40106 when toying too much with them
i'd swap the existing ICs with fresh ones, and parallel to that, check for power shorts... touch the ICs if they are hotting up

[Radamus]

Q1- Are you using a 4066 or a 40106? ..the schematic calls for the second, and yes they are different
Q2-You say 3 IC's, are you sure?.. the schematic has only 2, a 386 and 40106

386 and 40106 in circuit, 4066 as control.

The 386 may be oscillating? Can I replace it with another op amp? If it is, how do I fix that?

To me it seems like the power adapter is the culprit.  You *need* to try with a 9V battery (a 12V battery would be OK).

It did okay in the breadboard with the same power supply. I'll grab some batteries just to check. I didn't realize it was 13 until after I'd been using it for a while.

[nordine]

The 386 may be oscillating? Can I replace it with another op amp? If it is, how do I fix that?

it may be, some cure this by swapping input from pin 3 to pin 2 of the 386 IC... now, you must use that same IC (btw, its not an opamp, so you can't put a lm741 instead)

[Radamus]

(btw, its not an opamp, so you can't put a lm741 instead)

Shows how much I know.

So, I'll try swapping that. If it's oscillating, does that mean it's already broken and I need a new one? or will I be able to still use this one?

Also, Can I use different inputs from the 40106 if others aren't working, or is that a sign that the whole chip isn't working?

Thanks for all the help. This is my first IC project. Before now, it was all transistors.

[Radamus]

Okay, I checked the 386 at the input and outputs and the hum gets louder from in to out, so I'm assuming it's amplifying. Does this mean it's not oscillating? and if it isn't, what is? The only new piece to this whole thing is the 4066. Do they oscillate (Probably a dumb question)?

I probed the whole thing and I pretty much just get the same hum everywhere. Input, output, potentiometers, almost every lead of the IC's.

Can I get some tips on how to attack this problem? Do I just need to start over? I have an extra 40106, but only the one 386 (which is weird because I need one for the ugly face, too. Must have slipped my mind when ordering).

Any recommendations are greatly appreciated. Thanks.

[Paul Perry (Frostwave)]

Well, run it from a battery, not an adaptor.

then if there is STILL hum, either something in the circuit is humming by itself, or there is hum being fed to the input..
or (who knows?) maybe the input cable is not properly earthed (grounded). Because, if that is so, then yes you will get mega hum.

Another handy thing to have for testing: a 1/4 inch plug, with a 10k resistor inside connectign signal and ground.
That is so you can have a "silent" test signal going into an effect.. if you hear anything when that 10K test plug is the signal source, then you know that your circuit is misbehaving.

[stm]

Something that has caused me hum problems in the past is having the SIGNAL and GND (TIP/SLEEVE) leads the input or output jack interchanged. Hard to find, as you usually concentrate more on the circuit rather than the wiring!

[Radamus]

They're those nice internal jacks, so I'm pretty sure they're in the right place. I picked up some 9volt batteries today, so I'll try it with those. At any rate, I need another 386, so I'll just buy a few when I get to it and try swapping it out. I'm using sockets from now on.