Is my PFC controller IC damaged?

[cupoftea]

Hi,
The PFC gate driver output of the ML4800, (PFC controller IC) is measuring 190 ohms (with red and black DMM probes either way round). The ML4800 is soldered to the PCB, with all the other auxiliary components around it. However, i have removed everything connected to the actual PFC gate driver output itself.

Would you agree that the ML4800 chip is Kaput?

(Its in a 750W PSU which was returned with a blown input fuse. The PFC FET gate drive protection zener is also short and actually looks damaged. The ML4800 PFC gate drive output actually drives an external NPN-PNP totem pole, which in turn drives the FET gate...(but as discussed, i removed everything connected to the gate drive output before DMM'ing it)

ML4800

https://docs.rs-online.com/cda0/0900766b813e3fbe.pdf

 

[cupoftea]

Just measured it on another PSU...and it was MegOhms (the ML4800 gate drive output). So i guess the unit i'm looking at has a dead ML4800.

 

[cupoftea]

Do you think the question of the top post is sensible at all?...or does it represent that i know zilch about electronics? ..Often, as you know, for cost's sake, you find yourself having to probe returned_failed electronics with whichever particular component in circuit, with all the other components around it...then you have to make sense of the DMM readings. Then there's the fact that the DMM applies some voltage to the circuit, and any IC's may get their silicon junctions "woken up" by this, and one can then get "interesting" readings. I mean, if the silicon in an IC gets "woken up", such that he [measurement voltage]/[measurement current] = 180R, then that could make you think its a failed IC, when it might not be.....then there's the fact that different DMM's have different voltages...some may actually forward bias the ESD diodes in ICs, etc etc.
I've searched the web for good guides on this, but any known ones gladly recieved

 

[Easy peasy]

the fet it's driving could be kaput - unless you isolated the gate ... (?)

 

[cupoftea]

Thanks, yes, there was nothing connected to the gate drive output, i unsoldered the FET, etc.