One of the editing computers has has an odd fault for some months. It wouldn't turn on instantly, but the delay depended on the weather. On a warm summer day it took maybe 2 mins. As the autumn progressed it might take 5.
All of the studio is powered down at night so when a computer is turned on it is starting from cold. When that computer suddenly stopped yesterday in the middle of an edit and would not start again it was time for some fault-finding. (Yes, the project had been recently saved).
Swapping power supplies is easier than swapping motherboards so that was the first step and it was the right one. The computer powered up again. Not only that, but it started immediately, so the strange 'warm-up' fault was also down to the old power supply. Not sure what might be temperature-sensitive in a computer power supply but whatever it was, the problem is now gone!
For anyone contemplating a change of power supply, a recommendation is often useful. As I wanted to continue editing as soon as possible I used Maplin's 'order online/collect instore' system, which ensures that an item in stock will be held for you for a day. Ordered at 07.45, collected at 09.45 and computer ready for editing at 11.45.
One reason why I have always been attracted to the IBM PC design is because it is effectively a kit and well within the capabilities of a home builder. To change a power supply is just four screws and seven or eight plugs
I bought Maplin's 'own brand' 400w PS (£24.99) which adapts to various types of ATX motherboard. The original ATX used a 20-way plug. Then an extra 4-way was added to separately power the CPU. Then the 20-way was increased to a 24-way. The Maplin unit adapts to the various formats by having a 24-way where a block containing pins 11, 12, 23 and 24 can be slid out of the way if required, to leave a 20-way. It also has the 4-way CPU power plug and 2 x SATA as well as the usual Molex and floppy plugs. One quiet fan rather than the two in my previous PS means that overall the computer is actually quieter.