Build Your Own Clone Message Board

I am pretty new to building pedals, and I just completed at OD2. I think it might just be a problem with my trimpot settings, but I am not sure. I have the trimpots set to the standard specs. When I try to turn the overdrive level, tone, or drive knobs up past about halfway, they start doing a kind of frequency sweep and making fuzzy feedback noises. Does this sound like a trimpot issue or is something wrong with my circuit?

Also, the boost level knob basically only turns the pedal from completely off when turned all the way down and only goes up to the same level as when the boost is turned off when I turn it up all the way. Any suggestions?

Could be a trimpot issue, but several other possibilities exist. Really need to see photos of the build: viewtopic.php?f=50&t=6405

You might also want to read about the trimpot settings in my OD2 FAQ.

Here are some pictures.

This first image shows a resistor that might have been overheated when I was soldering. It's the 220ohm. Might be a problem?


Here are other images of the build:

Try turning the MAX and MIN trimpots so that they both have the flat face pointing straight down toward the footswitch end of the pedal. And turn the LOUDER trimpot so that it directly faces the brown 1uf film cap to its right. See how the pedal behaves then.

The singed resistor should be OK--they're very durable.

That is how I had the trimpots set originally, and I tried them at those settings again, and I am still getting the same issue. However, the boost level is now working correctly.

I also realized that the tone knob is adjusting the tone correctly, the drive knob is adjusting the drive, and the overdrive level is changing the overdrive level like they should. It is just making a lot of noise in the background when I turn the overdrive up much at all and then try to add drive or adjust the tone. The guitar is still coming through clearly, but there is just a flat gritty tone in the background when I am playing and that tone just continues when I stop playing. The tone get deeper as I add overdrive or drive. So it seems like the pedal is working, there is just this nasty noise that sweeps up and down when I mess with the knobs.

A lot of your soldering could stand improving. I see several questionable solder joints and the pots and switches looks pretty skimpy on the solder.

Are you powering the pedal with a battery or power supply? If power supply does it have a regulated output or is it a garden variety wall wart type?

Adjusting the trimpots should not have an effect on how the boost works since it is a separate circuit from the overdrive that just happens to be in the same box. It does sound like you have some instability in your pedal and it is just taking off and oscillating on its own. Stephen has a point - it could be ripple from an external supply.

Seems like the sort of problem that could be hard to fix without an oscilloscope. Have you tried a different op-amp? The standard kit comes with an alternative OP2134 doesn't it?
Might be a problem with the 51pf C3.

I beefed up the solder on some of the weaker looking joints and reflowed everything again, and I still have the same problem. I tried the other opamp as well, and the problem was the same, but it was a little worse and more sensitive.

I just have a cheap power supply that I am running my pedals off of. I didn't install the battery strap because I figured I would never use it. But I might try that...

So I was working on some more joints, and I think the 220ohm resistor that I thought I just singed was actually partly separated on one end to the point where it was almost in two pieces. Could this still be completing the circuit but causing the unwanted noise and instability?

As far as I can see there is only one 220 ohm in the circuit which provides an AC path for the tone control wiper to ground. Yes I think this could be the cause of your problems. You should of course replace it.

i think your problem is you have both the LED and both the tantalum clipping diodes installed, doesn't the instructions say to use one or the other but not both?

"Step 4: Add the 3mm red clipping LEDs. The LEDs will have one lead that is longer than
the other. The longer lead goes in the square solder pad hole. The shorter lead goes in
the round solder pad hole. DO NOT add these if you plan on using the MOSFET
clipping. You cannot use both at the same time. You can only use one or the other."

No, he's fine. It's "either/or" for the red LED clippers or the pair of MOSFET clippers--he has the LED's installed, and the MOSFET spots are empty.

BTW, there are no such thing as tantalum diodes--you're probably thinking of the tantalum capacitors that are used in the OD2, but they have nothing to do with the clipping stage.

your right, i was a lil drunk when i posted that!