Tektronix 7834 storage scope PSU help

[richnormand]

Tektronix 7834 storage scope just idling along and poof! The scope fuse just blew up, hard. Was not doing a measurement at the time and there were not any transients on the line that disturbed anything else on the bench.

The line rectifier bridge test OK as do the two main electrolytics.

Next step was looking at the two 2N3902 switching transistors. Both are gone with a dead short between base and collector. Open on everything else.
So it does look violent but what?

Before digging deeper are there any Tek gurus here that would know of such an history or issues with this version of PSU?

Cheers and thanks.