"Continuity testing usually won't find a bad solder joint"

I'm still in the process of figuring out why my General Guitar Gadget Reverb pedal doesn't work.

JD from GGG tells me that continuity testing usually won't find a bad solder joint. If the meter beeps, it means that there is a connection ... what more do you need for the pedal to work ?

JD adds that I'd rather need a good light and a 10x loupe.

Is there a systematic way to proceed ?

The best way to proceed would involve some equipment. With a scope, signal generator, and some spare parts, this could be cleared up in minutes.

A simple audio probe, as supplied by BYOC, would work also. One of these could easily be improvised. The idea would be to follow the signal from the input to the output, and see where it goes wrong.

here is a link to some pics of potentially cold solder joints

http://www.tangible-technology.com/articles/joint_update.html

and another

http://softsolder.wordpress.com/2009/07/03/cold-fractured-solder-joints/

in all likelihood you're going to need some magnification

This worked for me on a 5E3 build. It might work for you

I tapped on every solder joint with the end of a wooden chopstick while the amp was powered up. Got a loud thump when I hit the bad joint. Joint didn't look bad to me, but re-flowing it fixed my problem.

I'm going to reflow the solders first. Then look how to build an audio probe.
But, big But, there is a large part of the circuit that is inaccessible to me : the digital audio-brick ... And from what I've heard when pedal is engaged (a strident high pitched self-oscillating feedback kind of sound) there might lay the problem.

Understood - that's why I mentioned 'some spare parts' above. If power, ground and input signal to the module are correct - swapping in another module would be a good next step. Without a spare module, another thing to try would be removing the module, and seeing if that stops the noise.

Without a spare module, another thing to try would be removing the module, and seeing if that stops the noise.

it stops the noise I get almost the same signal as when by-passed without the reverb ... :mrgreen: