Norsk Data Nord-10/S restoration effort on the way!

I check the PSUs of machines that I own and have run before if I've not powered them up for, say, a year oe more.... It doesn't take long to do (especially not if you're familiar with the machine and/or have schematics), putting right the damage can take a lot of time and money. Most of the time you'll have no problems, sure. Most of the time when I get a machine on the bench (wheter a 'new toy' or something from my existing collection), the PSUs behave perfectly on dummy load. But if something does got wrong, you really don't want to kill all the chips.... There is anotehr issue, actually. PSU problems -- marginally low votlages, ripple, and so on, can cause all sorts of odd behaviour that will take hours to find if you don't initially suspect the PSU (like the time my PDP11/45 would run for 1botu an hour and a half before falling over in all sorts of odd ways -- I traced that to a '+5V' supply to the memory that was actually about +4.6V). Checking out the PSUs can eliminate such problems. That would not be enough for me. Heck, the assurance of the designer wouldn't be enough for me (and nor, for that matter, would anybody else's assurance). The risk is just too great. Sure the PSU will have built-in protection -- all decent machines do (although HP omitted it from their desktop calculators for some unknown reason -- the HP9815, 9825, 9832, etc desparately need a crowbar!).But I'd rather not rely on it. Better to be safe than sorry. All you need to do is disconnect the PSU from the machine, connect it to dummy loads (car bulbs are what I noramlly use -- 6V ones on the +5V line, for example) and check the output voltages. You don't need to investigate the internals of the PSU unless there's something wrong. -tony