Thursday, October 6, 2011
Second Son of Judybox Project Underway
As part of the retro mod Son of Judybox project I acquired for a Franklin an allegedly defunct Champion 600 that arrived this afternoon from beautiful downtown Cody, Wyoming. As it happened this was because the preamp tube had come adrift. Once reinstalled it was fine.
After some fits and starts the first Son of Judybox project turned out to be a good exercise in repurposing, but the objective here is a little different.
I want to try and reuse the Ningbo Chaobo (I ain't kiddin') transformers and compare the sound to the fully retrofitted 600, because if I can, I can lower the price of this modification substantially. The original power transformer does not have a 5v rectifier winding, but if it can stand an additional 600ma of heater load I figure a 6X5 rectifier tube will do swimmingly. I could use a 6X4 but with my fingers I need octal territory to work in.
So the objective here will be to measure the original filament voltage with no tubes and then with tubes to establish a baseline voltage and then install the filament string to measure the draw and test the power transformer temperature. The original load, according to the Sylvania manual, should be about .75 amps and the design load adds up to 1.35 amps, the difference being the .6 amps that the 6X5 draws.
The other idea I have is to use one of Ted Weber's 6x9" oval speakers he engineered for the Valco crowd.