A customer offered this vintage German model train controller for a chassis and OC44 transistors for a Tonebender style fuzz. It couldn’t really go wrong.. 
The chassis originally housed a variable transformer which controlled a model train. These were made by Trix in Germany probably somewhere in the ’50s. To make the chassis suitable for a pedal housing, I made some metal panels for the pots and cut some parts from the bottom cover to make more space. The two parts of the bottom cover then had to be soldered together to be held in place.
The original big knob needed some modifications to fit to a regular 6.3mm pot shaft. The circuit was designed on perfboard which was cut and painted black for better looks. We based the circuit on the Eqd Black Ash Fuzz (which is based on the Tonebender Mk2) but we had to use PNP transistors, add an external bias pot, a Tilt style tone control and two switches to choose between Germanium OC44s or silicon metal cans for the two last transistors.
Pnp transistors can be used with positive dc supplies if you reverse the polarity in the circuit, it’s a known trick for Fuzz Faces: http://www.muzique.com/lab/fuzzface.htm The two switches alternating between silicon or germanium transistors was an idea borrowed from the Texas Square Face Fuzz that was built for Stevie Ray Vaughan by his amp tech Cesar Diaz.
Ready to button up and be delivered to it’s owner. Schematic glued on the bottom cover in case someone has to repair it in the future.
All in all it was a project I really enjoyed and I think turned out pretty nice.. Check the demo below!
