Hmmm.... switched on my MSO5000 to check something about it for someone (it only has about 20 hours of use), after about ten minutes on it powered itself down and I was left with a repeating click and short LED panel flash every second or two.
Took it apaaaart, there's a near short (0.4 ohms) on the PSU connector's 5V pins to ground on the main board.
PSU seems to supply voltages fine.
After giving it a visual, there was not much to be seen so I made up a cable to my bench PSU to power all the 3 supplies (5V, +7.5V, -7.5V), sure enough the 5V was shorting. By the way, the connector is the same as a normal PC ATX connector cut in half, so I made up a cable.
After a bit of manual probing of the obvious power supplies, I got nowhere, the Schottkys all seemed fine.
Got out the IR cam, and the perp showed up like a Christmas tree. Looks like the ISL8203M 3.3V SMPS is dead. I didn't immediately look at this because #1 eyeball was looking for inductors: this device interestingly enough has integrated inductors, quite a feat, I've not seen this before.
So a replacement device is on order.
Anyone else had a similar problem?