Ok here is a qick and dirty schematic and PCB drawing of my powertech 20A 13.8V unit. I'm still waiting for Q1 & Q2 to arrive from UTS to fix my unit.
I've replaced caps, some diodes but not really a lot. It's an easy system to repair and as noted there is little to none in the way of voltage and current foldback.
The drawings are really quick and dirty forgive me but I've included a zipped file of the PCB/Schematic for eagle PCB cad. I've done some poetic justice to some parts used....in lieu of drawing my own switchmode transformers.
Hopefully my transistors will arrive soon.
Brendan