Identify unmarked diode

[newjackruby]

Hello,

I am tracing the circuit of a 1980's distortion pedal, and I've got everything ID'd except for the diodes. There are four of them, they all appear to be the same, but they either have no markings or they've just lost the marking in the last 35 years or so.

When I test them, I get around .565 volts forward and OL reverse. That's about all I know about them. I'm not sure where to go from here.

Thanks!

[antonis]

Consider any general purpose silicon diode..
(there is a rare case of being Zener diodes but it should be more rare the existence of 4 of a kind..)

Maybe more info about the specific pedal should be more enlightening..
(e.g. are they of some pair form and/or are both pairs inside a NFB loop or is some pair wired with one end grouned..??)

[newjackruby]

Okay, here's some more puzzle pieces.

The pedal is "Studio Series Distortion DS-01". I believe it was made by Washburn, or is maybe a knockoff (or first version) of the actual Washburn pedal, the "A-D2 Distortion". They also updated it later and renamed it the "A-D3 Stack In A Box". I was able to find a Stack In A Box schematic, but it is a different animal, as it has two 4558s, and the one I'm working on only has one.

Including photos of all 4 diodes in my box, front shots of all three versions, and the A-D3 schematic, which also has 4 diodes and identifies them. I'm thinking maybe I should just tried those diodes in my project as a starting point.

All thoughts welcome, thanks!

[TGP39]

They do look like the 1S1588 Toshiba Silicon switching diodes used in the KOT.