Troubleshooting a 5V Apple III

OK, so the replacement PSU was good when it was installed. However, this does not mean there's not a fault on the mainboard that's pulling one of the rails out of tolerance. Given that you have a voltmeter, I can't see any reason not to check those supply rails on the mainboard. I find it curious... All the books I have on electrronic troubleshooting and repair emphasisis that the only wat to put something right is to make measurements and think about them before you change anything. And yet it appears that these days you replace parts in an attempt to fix the problem without knowing if said parts have anything to do with the fault. You knwo, if I ever meet the guy who decided that board-swappign was a good method of diagnosis and repair, along with the guy who decided that soldering (or even surface-mount soldering) was impossible in the field, I am... well lets just say it has something to do with an induction coil and his reproductive organs ;-) Is the Apple III schematic on-line anyewhere? I might be tempted to take a look and suggest other thigns to measure/check. -tony