Awful Waffle problems

[ttolliver]

Hey gang -- I've reached the limit of my troubleshooting skill and thought I'd toss some pictures out in case something catches someone's eye.

When turned on the LED comes on, but the pedal passes no signal. There is no noise of any sort. It's as if the guitar is not even plugged in. When the pedal is switched off but the volume and gain are turned to max you get some noise. No part of the guitar signal is recognizable in the noise (it doesn't change when you strum) so it is just the hiss of noise. And you only hear it at the last maybe 15% of knob travel. But within that travel you can just discern volume changing volume as it should, gain changing gain, and tone changing tone. The LED goes on and off when it should.

Guitar cables have been checked. I tested all of the off board jacks back to the board, polarity of the LED, power jack polarity, correct direction of caps and the diode, etc. The ugly solder with a bit of a void in it is from a 100k resistor that kept reading around 63k that I replaced. It must have had an alternate circuit path available since it read 100k back on the bench. Behavior is the same before and after that replacement.

This is the first pedal I've built without one of the foot switch breakout boards. But I've double checked those connections a couple times. The TL071CP is a temporary placeholder while I wait for LM741s to arrive.

Anyway, give a shout with any advice or if you see anything suspicious.

Thanks!

 

[Robert]

Looks like the wires on your Input jack need to be reversed. ("IN" pad is connected to the ground lug)

Output jack appears to be OK.

 

[ttolliver]

Thanks!!!

And now is where I admit that I originally built it the way you say. But then while troubleshooting convinced myself they were reversed and swapped them. And then took these pictures.

I just swapped them back and I'm back to the original problem.

The LED is on when the pedal effect is off, and vice versa. The pedal doesn't sound right either...but it's only fair to withhold judgment on that until I get a LM741 in place. I understand the slow and noisy characteristics of the 741 are necessary.

 

[Nostradoomus]

LED looks backwards, that’s the old board style LED pad. Cathode (flat side) goes to the circular pad on those.

 

[ttolliver]

Thanks @Nostradoomus.

I swapped it and no luck. No light from the LED at either foot switch setting. Thinking I might have fried the LED I replaced it and still no luck swapped that way. The LED is definitely involved in the problem, but it's apparently not the only problem. FWIW, I definitely have the generation of LED graphic below.

I'll sleep on it and take another run at it. I have a buddy here in town that's built one of these I can borrow and eyeball too.

Thanks again for the help.

 

[falzhobel]

I "regularly" break some PCB while working them... The trace are very fragile and using the iron near those pads may break them.

It takes another level of diagnostic here since you need to trace where your signal is lost...

 

[ttolliver]

That's a great reminder @falzhobel. It has been in the back of my mind to grab another PCB and take a fresh run at this one.

Knock on wood, this is the first build that's given me problems. Well, if you don't count accidentally forgetting to drop the ICs into Brown Betty before the first test