Headscratcher: a mysterious MFZ-1 failure

[lincolnic]

So I built this MFZ-1 for someone, from the Tagboard Effects layout (I'd link it here, but their search function seems to be broken at the moment). It was perfectly functional on the test rig, boxed it up, still fine, stood in the room while he tried it out, no problems.

Then he went to take it on tour, and it stopped working. He thought the footswitch had failed, so I figured I'd just replace it, but now that I actually have the pedal back in my possession it's much stranger than that. When the pedal is engaged, the LED flashes once and doesn't stay on. The signal cuts out entirely as well, but bypass is still fine. I was guessing that maybe the switch wasn't holding the connection on the effect side, but it shows continuity on the proper lugs when it's both engaged and bypassed according to my multimeter. Nothing's shorting out that I can see - I covered the bottom of the vero with electrical tape in the boxing process.

No pictures at the moment, but does anyone have any ideas about what might be going on here? It's too late for me to really dig into the thing and poke around, but if anyone's seen this before I'd be glad to hear about it. Again, this was a completely working build...until it wasn't.

[lincolnic]

Little bump. Any thoughts?

[rullywowr]

Sounds as if it may be shorting somewhere. If the pedal comes on for a second then goes dark with no audio there may be a direct short to GND.  Did you check continuity between +9v and GND?

[midwayfair]

Could be a bad cap in the power section. Power comes on, cap tries to charge, then slowly shorts to ground. It would cause exactly this behavior.

[lincolnic]

Good thoughts, guys. Thanks to you both.

Ben, I can confirm no continuity between +9v and ground.

Jon, I'll definitely investigate the power section caps, but why would that affect the LED behavior? If it's still getting a ground connection through the 3PDT, and still getting power from the power supply, wouldn't the LED stay lit when the switch was engaged? (For the record, in case my original post wasn't clear: the LED currently flashes once when the effect is engaged, it's only staying lit for about as long as it takes for the 3PDT "click" to sound.)

[alanp]

I had those symptoms once -- the 9V wire had gotten squished between a pot and the enclosure. Probably not your cause, though.

[lincolnic]

So I finally got to give this another shot today, and was able to solve the problem by reflowing the ground connections on my 3PDT and input jack sleeve. Having previously fixed a Distortion + with similar symptoms in the same way, I figured it was worth a shot. And it worked! I'm not sure if the pedal got knocked around in transport (its owner took it to Australia), or if I just had a cold solder joint that took a while to manifest.

Then, just for the hell of it, I went and did the same reflow to my Triangle Big Muff that mysteriously stopped working a while ago, and brought it back to life too. Clearly, I'm not spending enough time on my ground connections!