Went to do the first smoke test of the tracking system after I put it back together, and the magic smoke came out with a bang. Two of the power transistors blew their cases, so what to do.
I pulled out and connected one of the small IC trackers, and after one try it went bang also.
The problem seems to be the back emf on the trailer wheel, as the tracker reverses direction when at the null point, the transistors can take a good surge of current. I made a dual full bridge from 10A power darlingtons and drove it with the IC tracker board. Works well, and the heat sink hardly gets warm.
I found that we needed better pointing accuracy so I made two shade mask to partially shade the sun sensors so even the slightest angle will cause the signal to be large enough to run the tracking wheel.
Next for the grill mount and first cooking trial.
Will look into a better power amp for that axis.