Thread: Rework of the 5v to 24v relay driver

Originally Posted by Bob Willson

The 1GBTs are power transistors aren't they?

Yep - a bit like a cross between a bi-polar transistor and a MOSFET. (IGBT stands for Insulated Gate Bipolar Transistor.)

Does the part have to be removed to test for shorts, because if not, then I can do that fairly easily?

This sort of depends on the circuit, and what other circuit elements are in parallel with the pins being tested. For instance, there may be a coil connected between the collector and emitter, or even between the emitter and the gate, which would cause a low reading too, much like a short. Generally, though, test between each pair of pins with the DMM set on a low-resistance range, and if there is a measurement below about 1 ohm, the part should be removed and tested separately.
Unfortunately, without a schematic, it can be near impossible to work out what's connected to what on modern multi-layer PCBs and sometimes even what individual parts are.

Edit: I assume it's the (U,V,W) motor outputs you're referring to, but are the other, (250VAC, 30VDC, 24VDC and frequency), outputs working?

N.B. Do the resistance tests with the power disconnected, or some of the smoke might escape from the DMM, making it useless.