Cunningham Zonk/MK1

[Bambalam]

Hello,

I am trying to understand this particular Zonk/MK1 build. There is a switch that toggles between Zonk and MK1 mode (changes out that first input capacitor - a lower value for the Zonk and higher for the MK1). There is a wedge version that only runs on 9v and there is a pedal board version that runs on a battery or power supply. It looks like the builder is fine tuning the bias with non standard resistor values and a trim pot.

There are many photos available on the builders instagram account. I have traced what I can understand of the circuit, but it doesn't match what I expected to see; the Hornby Skewes Zonk Machine and the Sola Sound MK1 Tone Bender that the builder says it is based on. I see a difference in the resistors coming off of Q1 and Q2. I'm unsure about the off board wiring and the use of the trimmer in the pedal board version.

Did I trace it wrong, draw the schematic wrong or is there something else?


Thanks.


Q1 Transistor = Texas Instruments 2N1307
Q2 Transistor = Mullard/Valvo Black Glass OC45
Q3 Transistor = Texas Instruments 2G308






My trace and schematic drawings.



Sola Sound MK1 Tone Bender and Hornby Skewes Zonk Machine Schematics





Pedal Reference Images:
https://drive.google.com/drive/folders/12Rn-GLys2jhJ9U0bDUycsW0DAXA1k-Kk?usp=sharing

 

[andy-h-h]

Hmm... The image on the bottom right. I think can see a normal looking MKI / Zonk style input. Cap to Q1 base, 1m to ground, 8k2 on emitter, cap from emitter to Q2 base etc, 2k2 on collector fo Q2. I'm sure some resistor values have been tweaked a little elsewhere, but I'm not sure I'm seeing what you are seeing schematic wise.

 

[Bambalam]

Resistors differ on each transistor cap.

Trace: Q1 cap resistor, Q2 cap no resistor and Q3 cap no resistor.

Sola and Hornby: Q1 cap no resistor, Q2 cap resistor and Q3 cap resistor.

 

[andy-h-h]

Looking at the tagboard version - I'm seeing a regular looking MKI / Zonk type circuit with nothing out of the ordinary. The input switch just adds a 0.0027nf cap in series with the 10n cap, to reduce the value down to the Zonk range. It's the same topology, with some different value resistors.

The pedal board version has a capacitor in series with a trimmer - my guess is that this is a simple tone control on the output, not unlike the original Marshall Supafuzz based on the MKI.

This is what I see on the tagboard layout, using the various pics on the google drive link as a reference. I'd say there will be variations of all the usual resistors by the builder.