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Old 8th May 2020
Here for the gear

It's obvious the tranny has failed. 12 VAC on the primary. Notta on the secondary.

As mentioned, she's powered from a 12VAC source. This voltage is handled (rectified) on its own path. Quite convenient to rectify and use this 12 VAC to provide filament voltage (AC). Completely separate from the high voltage step up.

In my early days of prototyping tube pedals, I made use of reversing tranny directions to achieve various secondary voltages in the back to back configs. Done it may times. As time passed, I began to use dedicated step up trannies to do the job instead of the earlier (but workable) primal approach of reversing tranny orientations. Many trannies are available to attain a myriad of secondary voltages tailored to my projects at hand. nothing new there, really. My interest is in knowing what the exact original design specs were in this particular pedal. Should I not get the answer, I'll press on with making a selection (as I always have) to produce the desired rectified high voltage. There's plenty of room to work with as the DC variance isn't that impacting on the gain, as proven out in the tube curves. Plenty of room to use whatever DC plate voltage I desire. SO,...I've no concern in getting here back on line with a proper step up using a 12VAC primary source. AGAIN, my curiousity was in knowing what THEY used in the original design. Should this be known, I contend it can very well be returned to stock easily.
On the other hand, my tasks are often to modify what is before me, for what I want, and can easily order trannies to take care of the task. No need to reverse connect but to use a dedicated (properly current rated) tranny to get me what I want into the fullwave bridge rectifier ,..filter,..then rock and roll with the plate voltages. If I can't make discovery on what was provided originally, I'll simply take the often used alternate repair/design path.

Merauder: your suggested DC voltage are well within the choices I would use (and do use in my designs).

SPecifically, curiousity is related to what THEIR stock AC secondary voltage WAS and an interest in whether anyone here KNOWS (has measured) the answer to the specific question.

Thanks for the input guys. Truly appreciated. Should I not get a specific answer, I'll simply press on with a tranny selection of my choosing.

Again, this internal tranny has nothing to do with filament provisioning in any way.

I'll give a bit more time for input should I run across someone who knows , and has measured, the original design.


My best,

Doyle Sheppard, E.E.
Sheppard Designs