direct drive coils, only one bip373 getting hot

[nsusammyeb]

Directly driving a ford coil pack in wasted spark mode. We have steady rpm signal and steady fuel injection and spark on two cylinders. However, the other two cylinders will fire but the transistor gets hot during cranking. We tried going not inverted and both transistors get hot, so we know our settings are correct.

Here is how we have it hard wired in.

U1 pin 8 to 330 resistor to left leg
center leg to spr4
right leg to ground on r37

U1 pin 7 to 330 resistor to left leg
center leg to spr3
right leg to common ground next to 5v commons

at a loss for words at this point.

[dontz125]

Which BIP is getting hot - pin 7,or 8?

Check the mounting of the troublesome device; look for security to the heatsink, thermal grease on both sides of the mica insulator, proper fit of the insulating collar (if using steel screws), no burrs shorting to the tab.

[phoenix3d]