/diy/ - Do It Yourself

>>1895666
>While unclipping the neg probe I caused a spark
That means a reasonable amount of current was flowing through that lead, or at least through the tip of the probe. If you were probing for current then that's perfectly normal, but if not then you shorted two adjacent contacts with the probe. Happens far too often, especially when probing directly on ICs.

Looks like the circuit is a pair of full-bridges (with all NPNs) and you'd have shorted either B+ to B-, or one driver output to B+ or B-. Probably something to B- as you were working with the low-side transistor. This could have damaged either the drive transistor Q2 or the power supply output (especially if it has a linear output stage), so I'd check both. It could also have damaged Q1. So just measure the voltage on the supply rails (AC as well to ensure the ripple is low) and the output voltage of the half-bridge in question, should be near halfway between the rails at idle, and similar to the other half-bridges.