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_diode

My 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 !

Sorry Joe : a bigger picture below...



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Hey Joe (OK it sounds Hendrix...  :)

Yes, the Ceriatone Forum seems somewhat desert... It shoudn't be, considering the models and the building/components quality available from Ceriatone. Not "hype" enough ? Inexplicable...  

You will indeed have to improvise some details according - or not ! - to your experience of amp builder... There's nothing major about the OTS : the layout is well done and alongwith the schem, you should manage all right.

A point I personally corrected - again, it's personal, right ? - I opined that the state of the PAB relay and OD relay were : Relays OFF => PAB or OD OFF. It's true for the PAB, but not for OD where you have Relay ON => OD OFF. This was not my taste, so I rewired the OD relay board in from NC to NO contacs, and voilà.

Another personal improvement I made : I used 5VDC relays instead of 12V, hi-speed wheel diodes instead of 1N400X, tight-braided coil relays supply wires, and of course 0µ1 caps across the back panel relay switch contacts. All this to avoid any switching relay noise that occurs when you switch on and off a relay coil (U=Ldi/dt).

A suggestion - if you allow me to do it - I would not start with the filament wiring first. Leave it for the last operation. Wire all the sensitive circuits before without being annoyed by the room taken by the filament wiring. Here's an example on my Serial Tone Killer. Fender - among others - used this technique :



At the left of the picture, you see a little pot which is the hum balance. It is installed close to the input tube. it allows to balance the filament hum much better than the classic 2x100R at the 6.3V Xfo winding. Again, this solution is done on the Twin-Reverb amps for years.

But it's only my advice, OK ? It's your amp and you decide !  

The "Serial Tone Killer" name is only a nonsense joke, as my project is derived frome a "Ceria Tone" set of boards. Nothing Else...  

And unfortunately, Joe, I'm located in France...   You can have a look to my small, amateur and non-commercial amp website, if you are willing to !    Type GUILHEM Amplification on Google and it should appear.

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Hello Jobewan,

So as a Noob to Ceriatone, what resources are available  for the build?

I did not build a complete kit like you, so I may not had all the ressources, but I'm akeen to think that there's not much than the layout directly available through Ceriatone website in the documentation page :

http://www.ceriatone.com/overtone-special-fm-modern-eagle-mod-50/

What do I get for instructions (if any) and what do people normally use for their builds?

The layout and a schematic, I guess - At least, that's what I have done, but my project is not the standard OTS100.

Ar you going off of the Layout doc only?

If you're building the exact kit, I guess yes.

Is there a schematic?  (I hope so)

A generic schematic OTS 50 is available. Email Nik : he'll kindly send you a .pdf copy - it's what I did.

and are there in process pics somewhere I can reference?

I don't think so, I did not searched for one since my project is not a regular kit. But see captainbackfire's thread : it should help you.

http://ceriatoneforum.com/overtone/my-overtone-special-50-build-(pics)/

Thanks folks.  I will take plenty of in-process pics and try to share them here.  I did donate to the board.  I hope it keeps going!

Good Luck ! Good idea too : It seems that we are not numerous to post on this forum these times...  

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Wiring is finished  :









The chassis is under measurement tests (and debugging  ) :



With used-less-than-average tube set, the power output stage reaches 75W RMS clean tone in Full mode (see scope waveform at left), 35W RMS in Half mode and 1W RMS in Home mode.
Measurements are made under 400Hz sine wave, at the onset of clipping, on a 8 ohms resistive load. That's a good start... 

Wait and See...

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Work is on progress  :





Wait and See... 

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Interesting way of making faceplates, Drpaedu - I note it !

I design mine via Inkscape, which is a freeware that generates vectorial drawings compatible with laser engraving machines, and after that, I have them laser engraved by local company specialized in signs and faceplates :







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Thanks for those detailled pics of wiring an OTS, captainbackfire.

Even if my Serial Tone Killer is a bit different, it may help to see what's done in an original model 

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Thanks Hayden !

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Continuation :

The chassis in now ready for wiring :



The fixation of the chassis in the cab is done :



Weight calculation :
- chassis and cab as above, plus back panel weighted at 16.0kg
- Eminence EM12N speaker factory spec'ed at 3.0kg
- tubes, wiring, miscellanous details estimated at 2.0kg
- Mains cord, FSW and its cable estimated at 2.0kg

That is to say a total at circa 23.0kg... We'll see !

Next step : wiring.

Wait and see !  

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Continuation.

The chassis is under drilling, assembling and populating :









First presentation in the cab :





Some chassis assembly detail awaits treatment, and I will be able to finish populating and start wiring.

So Wait and See !

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Thanks captainbackfire !

The works has progressed since then... I'm very slow by crucial lack of time !

The faceplates are engraved :



The 3 cabs are tolexed :



But the the first to be continued for the moment is the biggest one : the Serial Tone Killer...





Wait and See...

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I finished the cab yesterday :



Work is in progress, even if it's very slow... 

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The wood is in shape (and now painted black inside) - awaiting Tolex :





The faceplate is designed - awaiting engraving :



The job is done step-by-step, part-time, when I have time...

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Assembly is finished - minus the baffles :



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