IGBT gate emitted protection

[diag7919]

Hi there, I'm fixing a inverter welder, full of SMD. Found a shorted (across C/E) device, ST GWT60H65DFB.. there is a 5k1 resistor and zener in parallel across pin 1 & 3 (G & C), the Zener is shorted but I don't know what the voltage of this Zener is.. there are 3 other igbt with similar zener/resistor network. I removed one of the good zener's and on 15v diode range of my GW121 meter it show o/c.

I believe the maximum GC voltage is +-20v so I'm thinking this zener is probably 18v??.. does that sound about ok?, the zener K is on the gate
Regards

[diag7919]

I sussed it.. used process gen/meter on 24v output, connected up a 20k series resistor to limit current then measured across zener, guess I was right with my guess, 17.98v..