bobschwenkler
Well-known member
I'm working on the first MOSFET device I've worked on so far and I have a few questions about power MOSFETs. I think I know what the answers are, but I want to check with people who'd know before I go chasing my tail working to repair this amp.
It's a push pull amp and the power stage has ~+/-85 volt supply rails. The drivers for the power stage are medium power BJTs fed with pretty close to the same supply voltage. The same thing has happened in both channels (at separate points in time), so I'm wondering if there's an underlying cause, but until I get things back to normal I don't feel I can trouble shoot that possibility. The driver BJTs on the + rail went short base-collector, which then would have put the full voltage of their supply rail on the gates of the + side of the power amp and also probably the same on the - side of the amp.
I'm reading really low resistances all directions across the MOSFETs with a multimeter, which is totally wrong, right? Is it possible that this failure mode took out all of the power MOSFETs in this amp in one go? If it's relevant to anyone, the power amp is comprised of IRFP9240 and IRFP240s.
It's a push pull amp and the power stage has ~+/-85 volt supply rails. The drivers for the power stage are medium power BJTs fed with pretty close to the same supply voltage. The same thing has happened in both channels (at separate points in time), so I'm wondering if there's an underlying cause, but until I get things back to normal I don't feel I can trouble shoot that possibility. The driver BJTs on the + rail went short base-collector, which then would have put the full voltage of their supply rail on the gates of the + side of the power amp and also probably the same on the - side of the amp.
I'm reading really low resistances all directions across the MOSFETs with a multimeter, which is totally wrong, right? Is it possible that this failure mode took out all of the power MOSFETs in this amp in one go? If it's relevant to anyone, the power amp is comprised of IRFP9240 and IRFP240s.