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Hi all,
I have gotten the NostalgiTone 60s triple combo together, and the tremolo and fuzz sound great, but the overdrive will not pass any signal. I get some white noise if I turn the volume up pretty high, but whenever it is activated (regardless of order switch) no guitar signal.
Things I have tried:
- Made sure the TL072 is getting +9v on the correct pin and doesn’t get really hot.
- Replaced TL072 with another one just in case.
- I had kind of a hard time with the ribbon cable on the OD, and thought it might be shorted or compromised somehow, so replaced it with six wires.
- Checked for AC voltage at the input of the OD circuit (looks like the + side of R1) – seeing the mV increase when I hit a string.
- Checked for AC voltage at pin 3 of the TL072 – nothing.
I’m at a loss here and I guess I could use some troubleshooting hints. Pics attached but please let me know if any others would help.
Thanks!
Provide DC voltage readings at all 8 pins of The TL072 in the proper orientation.
I will assume that none of those yellow capacitors are Tantalum which have a small polarity imprint.
No, they’re ceramic (MLCC) caps from Tayda; the ones they sell are that color. I looked to see if a different cap got in there somehow, but none have the polarity markings like above.
Here are the TL072 voltages (as close as I can get, let me know if I need to measure anything else). This is with the switch active / LED on:
- 4.4v
- 4.4v
- 4.0v
- 0
- 4.4v
- 4.4v
- 4.4v
- 8.8v
That seems fine.
Next I would check foot switch connection pads to my main board connector pads with your DMM in continuity mode. Especially since that is an area you had to kludge a bit. I would put it on beep and check between pads to make sure there is a true connection.
If that doesn’t help I would start re-flowing solder joints all along the back of the main PCB for the entire OD section (every single pad). Just reheat the pad and let the solder flow for a moment. Have some extra solder handy if needed. It is really a very common problem to have a cold solder joint.
Be careful not to bend the potentiometers back and forth too many times or you will damage the leads. You will likely need to re-flow those pads as well after your through re-flowing all of the component pads.
Well, I figured it out… the switches checked out OK and I reflowed the pads, and when that didn’t help I started probing for continuity. I saw there should have been a signal getting from C1 to R2, and on looking closer the trace looked a little funny – turns out that was because it isn’t there:
So I tacked a wire on there, and sure enough, the OD works just fine. If nothing else I’m glad it turns out I put it together correctly, lol.
I’m glad you were able to figure it out!
I’m honestly perplexed by the issue, as many of these PCBs have been successfully built and shared here, including by myself. I’ve also sold quite a few finished builds without encountering this problem. While I absolutely believe your experience, I want to reassure others that this appears to be a rare, one-off occurrence.
To clarify, I took a picture of the back of the PCB I sell, and you can clearly see the trace.
So again, I am sorry you had an issue but happy you figured it out.
Oh yeah, I’m sure it was just a freak occurrence. And the board was kicking around in my “backlog” box for quite a while before I got back to it, so we can’t rule out that it took some damage during all that time.
Plus, like you said I’ve built the DSOTM combo and one or two other small things and had no problems with those. So no worries at all.
I think this happens sometimes in the manufacturing of PCB’s. I had the same thing happen to me with an Aion PCB for a Mk3 Tonebender. It just didn’t work right after building it, so I took out my diagnostic tools and spent nearly 2 freaking days trying to figure it out. I discovered that there was no connection between the leg of one of the transistors (Q1 Collector) and another part of the circuit (R3 Resistor) that was supposed to be there. I reviewed the schematic and the PCB, double checking everything and reflowed the solder joints twice with no success. Knowing where the problem was through continuity testing, I made a jumper for where the missing continuity was and voila – the pedal worked! Just a bad PCB. Aion has a solid reputation. I’m just glad this wasn’t my first ever project because I would have never figured it out and would have given up. You can see my jumper on the back of the board going underneath a pot. Stuff happens.
“I think this happens sometimes in the manufacturing of PCB’s.”
A trace not connecting properly to a pad could be but not an entire length of trace missing from the PCB, masking and all.
The PCBs are fine as shown above.
That is sort of what I meant – a trace not connecting properly to a pad. Upon inspection, the trace on the Aion board I built appeared to be totally continuous, but there was no continuity via my multimeter. So there was a break in the connection somewhere, such as a microscopic discontinuity somewhere along the trace. Building on vero I had a problem with a circuit not working properly. I found a tiny, nearly microscopic solder bridge under high magnification that was the cause.
By the way, I never have ever had any problem with a Guitar PCB board.
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