In one of the 828s that I look after, R5 has burnt out and gone o/c, momentarily (so I understand) taking the whole supply down with it. The device IC1 itself is not (at least now) s/c between pins 14 and 11/3, and on-board measurements (still with device removed) show that TR2 and 3 are still intact (i.e. not s/c C-E).
Is this something you’ve seen before?
With the device being obsolete, I’m proposing to dispense with P48 altogether, but have yet to get approval on that. I was just wondering if this is a known issue with this DC-DC convertor design.