Fixing blinking power light on an unresponsive Mac Pro is simple enough, but...

[atlanticza]

... it's a recurring problem. I've re-seated the Ram and Ram trays a number of times and my Mac Pro works well for a number of days (and reports the correct amount of Ram installed), then a day later or so, the problem occurs again at startup.

Is there something I'm missing here; is there some remedial action which would permanently fix the issue?

 

[666sheep]

It could be: defective RAM (most likely), riser (sometimes it happens) or logic board (rare). Check LEDs on RAM risers. How much sticks you have? If your Mac will start, check Memory status in System Profiler.
How many times LED is flashing?
Quote from service source:

1 Flash: No RAM is installed or detected. Or, the quick memory test failed. An LED will light up on the memory riser card next to the affected DIMM or empty DIMM slot.

3 Flashes: A RAM bank failed extended memory testing. An LED will light up on the memory riser card corresponding to the affected DIMM.

 

[atlanticza]

Many thanks for your response - I've learnt something. Next time it happens I'll check the LED status. (But so far, so good.)