Altair-what do I do first

Look, the chances that any regulators failed while the machine was sitting unused are VERY LOW. For someone who takes the time to ask what their first step is, suggesting that they begin by removing components from the boards boarders on the absurd. The risk of causing dammage in this process is probably much higher than the chance that there is any problem in the machine. Unless something is eating the etches off your board as they sat, a formerly running Altair really should not have any open grounds on its voltage regulators. So in this specific case, yes, your paranoid! I'm be far more concerned with the idea of someone new to computer restoration is being advised to start removing parts from boards on the astronomically unlikely chance that a 7805 ground has opened. The practical reality remains that most probably, the Altair will power up and run just fine after a good cleaning. New defective components are one thing, but we can assume that the Altair was working at one point, so unless something has gone wrong, it should still be working today. As for resistance checks, I have to strongly disagree Tony. If you verify that there are no shorts caused by broken decoupling caps, loose parts, and so on, then the chances are nothing rude will happen when you flick the switch, and this is the only point behind such tests. Resistance checks have absolutley nothing to do with testing the 7905 regulators functionality whatsoever, and that is not why such tests are a good idea before applying power. The regulators generally dont fail while sitting around. Getting a bad part into a new project is a very different situation than trying to return a formerly working machine to service. No practical set of testing, other than dynamic (functional) testing can detect every possible failed component. So the question should be, what is the PRACTICAL level of testing that should be applied PRIOR to powering up the Altair. In all the replies to the original post, now many suggested ANY testing at all? My point being, its easy enough to check the power supply filter caps BEFORE attemtping any snake-oil rejunivation methods, but this was not mentioned, and you seem to agree this is probably not needed here. So why does the list as a whole sit by while reccomendations of pulling parts off of boards float by, when this is one of the VERY LAST things a beginner in vintage restoration should attempt? I agree, many vintage chips are hard to replace. So don't remove them unless its absolutley mandatory to do so, after you have isolated a real failure. The idea of a restoration should be to do as little to the machine as possible in order to return it to its original operating condition. In the case of a S-100 box like an Altair, very little is really needed before you can feel quite safe about flipping the power switch, given that the machine used to run just fine. The bottom line is just this simple, "if it ain't broke, don't fix it". Quite different from the advice this Altair owner got from the list. Tony Duell wrote: <snip!>