Sound cuts out

[tomwaters]

Hope this is OK to post here. I've just built a chord organ from a PCB set from thonk as I had most of the parts. Its working when I first turn it on but after a varying amount of time the sound fades out and leaves some quiet noise.

If I tap the joints around the op-amp it comes back for a while but fades out again. It can work for anywhere between around a minute and a few seconds.

I've changed the TL074 and reflowed the points of the op-amp and most things in that area, continuity tested the dac to output path and can't see anything wrong.

I've used 1n4148 in place of the BAT42 and 10r resistors in place of ferrites but don't think that would cause it. Any ideas?

[tomwaters]

Looks like this is fixed after adding the 100k resistor - TomWhitwell/RadioMusic#70