Powering up a 20-year old MicroVAX II

Message: 20 Date: Sun, 22 Feb 2009 17:58:50 -0000 From: "Robert Jarratt" <robert.jarratt at ntlworld.com> Subject: RE: Powering up a 20-year old MicroVAX II <<Do you mean that it will be difficult to fix, even if I can find someone who really knows what they are doing?>> *Yes, it'll be difficult (but not impossible) to fix. You're probably better off finding another working one. Or trying to find an electronics buff.* <<I only have a basic multimeter so I don't know if I would have had the necessary equipment to do this, do you have any advice on the minimum equipment needed?>> *You don't have the necessary equip. And, No, I don't, because teaching you how to be an electronics technician is a whole other subject and beyond my means. * << Now that there has been some damage is it sensible to replace the blown capacitors and any other ones that don't measure well?>> *Not for you to replace them, no. It needs knowledgeable attention at this point.* << I looked up variacs but there seem to be an awful lot of different ones, again any recommendation as to the minimum I would need?>> *You choose them according to your voltage and amperage needs. I use a 5 amp one for small electronics and computers, 10 amp for larger computers (like my own Microvax). Again, though, unless you already know what you're doing with one, please take the time to learn prior to blowing stuff up. * <<By the way, I am aware that PSUs can be very dangerous to meddle with when you have limited knowledge.>> * Yep! They remain dangerous even when you have knowledge. * << How long should I leave the PSU between any tests to allow the capacitors to discharge? The label on the PSU says to leave it 5 minutes, I suspect it should be longer.>> *Honestly? Don't use time as a safetly measure. Assume the caps are always fully charged. Then test them and discharge them if needed. Again, because you don't know this, you need to get the knowledge or let someone else handle it before meddling with the PSU. Proceed carefully.* On Feb 22, 2009, at 3:33 PM, Gordon JC Pearce wrote: Gordon, you don't mention how many caps you've looked at or tested, or how you've done so, but I encounter them constantly. Not so much in the 1980's vintage DEC equipment YET, but it's no myth that AEC's are electrochemical vats that have a lifespan. The lifespan varies widely depending on many factors, heat being the big one. jS