I have blown a few in my time as well, some common reasons are;-
- Over lubrication of motor, this can dmage any motor but with digital it can lead to chip damage as well.
- Using larger (hoter) motors, the Scaley SSD chip is designed for 18K RPM motors and the biggest motors I have had success is 20K, the Slot.It SSD chip can handle up to 25K RPM's.
- Adding too much extra magnet can overload the motor.
- Motor shorting (bad motor) can also blow a chip.
- The SSD chip is also only rated to 16 volts so too high a voltage to the track can blow motors as well.
I had one particular car that blew 3 chips and I eventually tested the motor and it was sparking inside really badly, I think this meant it had a short in it and the easier and cheaper solution was to replace the motor.
There is a modification to repair the common blown chips types but you need to be good with a soldering iron as it is a real micro job. I have failed on 3 attepmts to repair a chip but I had one fixed but an electronics guy and it works great now and can handle hotter motors as well.
Hope this helps, blowing chips is a real bummer!