powering up older machines - is it safe?

I tend to err very much on the side of caution in this (and have had, shall we say, 'differences of opinion' with other list members about this in the past). I never just plug in an unknown machine to 'see what happens'. The main worry is not a capacitor Failing. The main worry IMHO is that if there's a fault in the power supply regulation circuitry then that could make the +5V line jump to a high enough voltage to wipe out just about every chip in the machine. Expansive and difficult to put right. Now, of course, this circuit could fail at any time, and most good power supplies have what's called a 'crowbar circuit' to protect against this. But I still feel that wehn you come to a machine that's not been used for some time, it's safest to disconenct the PSU from the rest of the machine, connect the former to a dummy load (a set of suitably-rated light bulbs) and test the pwoer supply separately. In some cases I've even made up test boxes/harnesses to test commonly-used (for me) PSUs quickly and easily. The problem (for you) is that doing this, on an unknown machine, takes some experience. You have to know how to disconnect the PSU from the logic (but leave the mains input connected), you have to work out suitable dummy loads and connect them to the right wires/pins on the PSU. Somebody elase here can probably talk you through waht to do, but it's still a bit of work. -tony