Naughty Fish Oscillating

[oldsoul]

I had this working but when boxing it up I must have done something because now it's just oscillating when I turn up the gain and or Volume.

[madbean]

Everything that's in the mV range on my voltages is basically ground. So, you've got a serious problem on IC1 and IC2. IC3 looks good and your LT1054 is spot on. So, first thing I would do is try a different IC. Unload IC1 and IC2, take you good IC in the IC3 spot and put it in the IC1 spot. Take another look at the voltages on it after doing so. If they line up with what's expected, then definitely those first two ICs are the problem.

If the voltages still read bad, then you need to start looking at your parts for wrong values, look at your soldering, esp. for any bad joints or hair traces, etc.

[oldsoul]

Thanks MB. I touched up some of the connections around the pots thats looked a little suspect. I fired it up, plugged a guitar in and it seems to be back to normal operation. Tomorrow when I'm more awake I'll make measurements and go through my soldering one more time and report back. Thanks for the quick response. I'm making this one for my brother as a Christmas gift so times ticking.

[oldsoul]

I fixed a couple of solder joints that were not looking awesome. Everything specs out perfectly and it sounds great. My only last problem is the volume pot is now not working.

[oldsoul]

Ok maybe my mistake. The volume pot is working but only at the bottom of its range. From full off no output turn to about 8oclock it adjusts the nothing after that. The volume just stays the same.

[oldsoul]

What sort of control  should I expect from the volume pot? I should add I used a 500K gain pot as you mentioned in the build notes not the 1M


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[madbean]

Do you mean the gain pot? The volume pot is an optional 100k at the end of the circuit. The Gain pot is at the beginning. In general, the Gain pot is not terribly effective in the first half of the turn. Using a reverse log taper (C) does make an improvement, but most of the really good action starts around noon onward.

[oldsoul]

I was referring to the volume pot. I did install a 100K pot


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[oldsoul]

Any thoughts? It seems like the volume pot should have more control. It just goes from almost completely dead  full on very quickly.

[oldsoul]

If I changed the Gain pot to 500kC should I change the VOL pot to something smaller like 50kB instead of 100kB? Also would changing it to a Log pot help?

[oldsoul]

Any thoughts on why the Volume pot has such limited range? It's either 0 or full volume in a short turn of the knob.

[madbean]

Sorry, I completely dropped the ball getting back to you. It seems like there might be something wrong with the volume pot itself. Any volume control should have a fairly gradual curve. Are you using a 9mm or 16mm? If it is a 16mm, you could try spraying some contact cleaner into the pot if you have any. Also, do you have a pic of the wiring of the pot? That might help.

[oldsoul]

No worries, I totally appreciate all the assistance.
The pot is a 12mm type. I don't have the circuit currently in front of me as it was given as a gift.
I will get it back this weekend and get you some pictures.