Schematic for Vesta Fire Digital Delay DDX Pedal

[pdf64]

I've got an old but working Vesta Fire Digital Delay DDX pedal dating from about 1990s, which has been pretty useful at various times over the decades.
But a delay pedal that would do wet only would be handy right now, so I'm thinking that it should be fairly simple to mod this to do that, provided that a schematic was available.
It's a fairly densely populated double sided pcb, so tracing the relevant areas of the circuit is somewhat trickier than with simpler, single sided boards

[Enzo]

So did you contact Vestax and ask if schematics were available from them?

[pdf64]

They went bust in 2014 https://en.m.wikipedia.org/wiki/Vestax

[Enzo]

Oh, too bad then. Sorry.

[pdf64]

So in the absence of a schematic, and the difficulty of tracing the circuit out from the double sided board, I tried feeding in a signal and using a scope probe, working backwards from the output jack, trying to identify where exactly the wet and dry signals were getting mixed together. I assumed it was going to be an inverting mixer, but it actually seemed to be a simple passive mixer.
Anyway, lifting R38 near the 9V jack achieved the aim of killing the dry signal, even in bypass mode.
So job done

I'm putting together an 'echo only' rig, so I can overdrive my main amp, feed a line out from its speaker signal via an isolation transformer into the delay pedal, then amp up the echoes from that with an old solid state combo that I picked up for free

It all seems to be working great but the proof of the pudding will be at a band session tomorrow.