Parentheses Fuzz not working - UPDATE: LED still not working

zipfool

Member
I'm working on building a bunch of these pedals and about half of them have this problem where the LED for the distortion circuit won't light up even though the circuit is making the right sounds when engaged.

I have mounted these "problem" PCBs in an enclosure yet, so maybe it's just a grounding issue. I'm testing them by hooking them up to power outside of the enclosure.

I have tried removing the LED in question and just socketing a new one in place and it still doesn't work...
 

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LOL, yeah I never imagined it growing to this level. One step further and it isn't a hobby anymore.
I posted an earlier build on a local gear group on Facebook and more than a few people asked if I'd be willing to make more :) .
 
you definitely need to get the LED sorted out. it the LEDs are working out of the box on some of them, they should be working on all of them. have you checked to see if you are getting voltage to them?
 
Bad batch of LEDs? Have you tested the LEDs by themselves out of circuit?

I keep a CR2032 on my bench for that. Handy for bi-colour LEDs, too, to get the correct colour orientation.
 
Did you double check that you have the anode and cathode correct? I’ve had a few LEDs over the years where for whatever reason, the cathode was the long leg instead of the anode— wasn’t until I took a look at the LED and saw what side the anvil was on that I realized that the LEDs had the leg lengths switched around
 
Bad batch of LEDs? Have you tested the LEDs by themselves out of circuit?

I keep a CR2032 on my bench for that. Handy for bi-colour LEDs, too, to get the correct colour orientation.
You might be onto something, and maybe I somehow fried the LEDs when I was applying the heat shrink to the legs.
If, when I test, the LEDs are getting voltage from the PCB—then I'll check the LEDs off-board to see if some of them are rotten.
 
Did you double check that you have the anode and cathode correct? I’ve had a few LEDs over the years where for whatever reason, the cathode was the long leg instead of the anode— wasn’t until I took a look at the LED and saw what side the anvil was on that I realized that the LEDs had the leg lengths switched around
I judged anode/cathode based on leg length, but I'll double check the actual LED bulb to make sure these aren't backwards. That would be a simple fix, provided my solder sucker does a good job cleaning it up.
 
I checked all LEDs and they're fine. But apparently each of the three boards suffers from a different sort of fuck up from me.

PCB 1: All Circuits make the right sound.
Distortion LED: 0v
All the others: 2.35v

PCB 2: All Circuits make the right sound.
Octave LED: 8.8v
All the others: 2.35v

PCB 3: no sound whatsoever.
Boost LED: -2.3v
All the others: 2.35v
 
One other thing that's weird: out if a batch of 7, these three were the only ones I tried to clean with alcohol once all the on-board components were soldered in. Couldn't have an effect like this though?
 
I doubt it was the alcohol, it evaporates really quickly. Status LEDs should be really easy to troubleshoot, there's not much that can go wrong. Take a look at this part of the schematic:

1623900334881.png

Check C100, R100, R101 and R102. Check you're getting voltage through D100 Check the joints, could be a poor solder joint or a bridge to something nearby, reflow if necessary.
 
I doubt it was the alcohol, it evaporates really quickly. Status LEDs should be really easy to troubleshoot, there's not much that can go wrong. Take a look at this part of the schematic:

View attachment 12786

Check C100, R100, R101 and R102. Check you're getting voltage through D100 Check the joints, could be a poor solder joint or a bridge to something nearby, reflow if necessary.
Thanks for the suggestions. I figured out the problem with PCB #3, so that's working fine now.

Both pcb #1 and #2 appear to have two totally different problems. #1 needs more extensive troubleshooting, so I'll just follow up on that later.

#2 is an interesting situation. The LED still doesn't work, yet D100 and C100 both show normal voltage (I think).

D100: 9v / 8.8v
C100: 0v / 8.8v

R100 is where it gets interesting. Before you ask, yes I did try to replace R100 and I got the same results. I also tried cleaning up the board around that area to ensure no bridges.

R100, when the foot switch is not engaged: 8.8v / 8.8v

R100 when the foot switch is engaged (Distortion is on): 8.8v / 0v

This is not what the other LED resistors measure at when engaged. For them, I get: 8.8v / 2.35v

So now I'm at a loss as to what's going on...
 
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Pinging this topic to see if anyone knows what values I should be getting on these components?

On a second look, I realized that the LED pads aren't getting the voltages I think they should.

I took the LED out and confirmed that it is working independent of the board.
Now, when I measure the voltages at the LED pads, I get 8.8V on both pads when the switch is engaged. Is that what I should be getting?
 
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Nope. You should be getting voltage on the resistor side and gnd on the switch side. If your switch is giving you 8.8v then it is broken or wired incorrectly
 
If you're getting the same voltage on both pads it could be a short, either in the LED or on the board. Could you post some close up pics of the pads, both sides of the board?
 
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