Altair-what do I do first

At 12:23 PM 9/29/02 -0700, you wrote: Yes and no. I used to be all in favor of sockets but what I've found over the years is that sockets generally cause more problems than they fix. Yes they make repairs easier but electrolysis bewteen the IC leads and the sockets cause problems in time, even to the point to where the leads will corrode completely through and fall off or break when you try to remove them. In addition, ICs tend to creep out of the sockets and have to be periodicly reseated. Using GOOD quality sockets (gold pins) and ICs (mil-spec parts) minimizes problems but are EXPENSIVE (unless you're a good scounger like me and can get them free :-). My personal opinion is to do like most of the good manuafacturers have done and to install SSI ICs directly on the board and install EPROMs, CPUs and specailized parts in sockets. That seems to a good compromise between cost, repairablility and reliability. Of course you can. All the arguments about removing ICs to check the regulators is rediculous! Who in their right mind would remove 50 to 100 ICs to test one part with only three leads! If they're THAT worried about worried about the regulators it would be MUCH easier to remove it and test it by itself instead of removing all those ICs! Actually it would. You're just powering the circuit from a variable DC supply instead of a variable AC supply and you're bypassing the transformer and retifiers. Maybe Assuming that the circuits are designed to operate off of 5 VDC, you should be able to safely start at that voltage or maybe slightly less and then increase the voltage to the rated voltage (8 volts or so for S-100 type cards) while monitoring the output. (In fact, you can take the voltage all the way to the input limit of the regulator as long as the regulator can dissapate the heat generated.) If you want to reform caps at the same time then start lower, say 1 VDC. Another advantage of using a bench type power supply is that you can set a current limit in case a cap or anything on the board is shorted and the chances of doing any damage are greatly minimized. The current limit setting is sort of a SWAG. On a fully populated board I'd probably start at 1/2 of the rated current of the regulator and probably have to raise the setting to get it to operate. On a board that's not fully populated I'd reduce the current in proportion to the percentage of ICs that are installed on the card. I generally keep notes on how much current various devices draw, If you ever have to test a similar device those notes give a good starting point. I use bench power supplies like this ALL the type, IMO they should be a repairman's second investment after a good meter, even before buying an O'scope. Or would undervoltage hurt some It's POSSIBLE that some IC or circuit might latch up and cause a problem but I'd say the chances of that happening is between slim and none on a TTL circuit. I have seen that kind of thing happen on CMOS devices such as HP calculators but even there it doesn't do any damage, it just causes the device to lock up. Bear in mind that at this point we don't care if the circuit is operating, only that there aren't any shorts or things of that type. Joe