Hey Joe & thanks !
I think I took pictures of the OD relay configuration and I draw a schematic. Let me retrieve (or redraw it) so I can post it here if you intend to do that little easy mod too.
About the "wheel diodes" (= "diodes de roue libre" in French) : it seems that it's called "flyback diodes" in US/UK. In a few words : a flyback diode is installed in // with the coil of a relay in order to null the flyback current ("extra courant de rupture" in French) due to the coil relay switching. That flyback current is responsible for the annoying to very loud "pop" noises that arises when you switch that relay on and off, and the diode is here to null it by shorting it. As this kind of current is a short but ample impulsion, you need a fast (high speed) diode for best cancellation. Here I used 1n5819 diodes.
You should easily find much complete litterature on flyback diodes in English on the web ! i.e. :
https://en.wikipedia.org/wiki/Flyback_diodeMy Serial Tone Killer is not a Twin, it's a modified OTS100, on which I added :
- a footswitchable digital EHX reverb unit with deported pot.
- a footswitchable integrated FX Loop able to deal directly with guitar FX pedals.
- a 1W "HOME" single ended EL84 switchable output stage.
- an integrated 4x9VDC regulated power supply for in-llop stompboxes.
- an extra filtering on the HV voltage.
I'm facing issues with the 1W facility : the prototype tested on my Boogie MKIIA worked amazingly well, but it sounds awfull on the STK, no matter the attempts that I made to cure the problem. Well... It's a bad wedding, so to speak... I will dismantle it, I think, and replace it by something else : I'm studying the possibilities.
IMHO, If you target to DIY a Twin-Reverb, do not choose the OTS route : the circuit is much different from the TR. Ceriatone probably have an offer in that field.
Also, considering that it's only your 2nd DIY tube amp, I'm really afraid that you would face many other issues by "following exactly my footprints", so to speak, with all my respect. I mean : assemble a kit is not the same as designing mods or a whole amp. If you finish and debug your OTS and C-Lator satisfactorily - not to say perfectly - let me tell you that you'll have taken a big step !
And for more detailed pics about the Serial Tone Killer, you can have a look to my Serial Tone Killer subject on the forum.
And yes, it seems that we are here like two survivors...
I'm located near the city of Lyon.
Cheers !