Another machine joins the merry throng.
The Belcat 503 is a cheap delay pedal which (I think) uses a PT2399 chip. (The printing on the chip inside mine was hard to read)
I didn't study schematics for the chip but instead used the Reed Ghazala prod it and see approach...
There are probably more bends to be found but I was happy with these - three of the bends cause endless oscillation to distortion. The other causes glitchy noise bursts.
There's an 18 minute improvised recording using it here.
Circuit bent quid bleepy keyboard
Circuit Bent Belcat 503
Resonant Lowpass Filter + Holy Grail Reverb Pedal (these were set at the start of the recording and not changed so all the sound manipulation is done with the 503)
Towards the end of the recording I introduced a homemade oscillator and my circuit bend/hacked crappy SK 322b.