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Zenman Tube pedal
Old 8th May 2020
Here for the gear

Zenman Tube pedal

Might anyone here know a bit about the internals in this pedal?

I've a internal transformer failure but cannot find prints or specs on this tranny.

The box is tube based, powered from a 12 VAC source.
Looking at the electrolytics' voltage ratings of 475 VDC, it's clear this pedal is running full on high voltage DC (no starved crap here).

I design and build my own tube pedals and use specific trannies with specific turns ratio to get my full wave bridge rectified plates but I want to keep this particular pedal STOCK.

No markings on the tranny and no response from the original manufacturer.

Peavey has bought Budda but supports no hardware prior buyout.

East Amplification provides no response to my queries.

Any help here as to the specific turns ratio (step-up) on this internal tranny?

Any help would be appreciated.

Best to ALL!!


Old 8th May 2020
Here for the gear

Well...keeping the pedal stock is not going to be possible since the transformer just died.

My best and educated gues is that they used a back to back principle and you probably wanna shoot for 200 - 250 volts. So find a step down PT with a corresponding secondary voltage and mount it in in reverse.

Maybe post a picture? People here might find it usefull

Old 8th May 2020
Here for the gear

it just came to mind that its probaly feeding the heaters from the primary side of the PT.
Can you confirm this? are heaters dc or ac ?
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
Old 9th May 2020
Here for the gear

Correction to previous comment!::

As to filament, i stated a 12VAC rectified feed for filaments which clearly doesn't provide AC filaments. Sorry for the confusion. I'll look closer at the topo as I did see diodes in the filments path, indicative of DC filaments. However, this feed is completely separate from the internal transformer. Inconsequential, as transformer in question is for high voltage only and NOT anything related to filaments.
Old 15th May 2020
Here for the gear

Morning to all.

Wanted to get a few pics posted and provide further commentary on this ZenMan project.

One can easily see the power supply topo beginning where the transformer of interest is located. This portion of the PCB Has the imprint BUDDA-PHATMAN, 1997, REV2.

The unit is the BUDDA, ZenMan, Pure Vacuum Tube Overdrive, from Zen Engineering. (4 stages). S/N000678

As mentioned, the 12VAC internal tranny has no output. Filtering in the supply is comprised of reservoir caps of X2, 10uF./450VDC. Next filter stage uses Nichon's (X2) 47uF.250VDC caps .Both using series dropping 1/4 watt resistors. The final (used) A+ and B+ are applied to tube's plates.

Externally powered by wall tranny (walwart) at 125VAC Primary and 12VAC secondary. Original supply rated at 1 Amp. Present Jameco is rated at 1.5 Amps.

The internal (failed) tranny takes a 12VAC primary feed and generates a secondary voltage that is still unknown. I still seek that spec but it (stock) appears to be elusive.
As mentioned, my client would prefer to repair in a stock fashion. Of course, my many options offers ranges of plate voltages, up to 300 VDC or downward towards the upper 100's. Am looking at a 12VAC tranny provide a nice 200-210 VDC secondary for full wave rectification.

STILL listening out for what that "magic" secondary "WAS",..but not waiting long on moving forward
Attached Thumbnails
Zenman Tube pedal-20200514_023146.jpg   Zenman Tube pedal-20200514_023303.jpg  
Old 15th May 2020
Here for the gear

The culprit (opportunity)>>>
Attached Thumbnails
Zenman Tube pedal-20200514_022715.jpg  
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