I had a problem with brick power supplies a number of years back. I found an issue that caused them to fail. I had about ten of them on the same power switch. You'd think this would not be an issue but it is.
You see it works like this, each one had a transformer in it. When you disconnect the power, with a switch, each of the transformers often has energy left in the cores. Normally for just one supply, this isn't an issue. When you have a bunch of these, only one supply absorbs all of the energy. When it does, it will blow some part of that supply up. On the ones I had, it'd take of the negative rail. I put a MOV on the power rail and didn't have any more issues with power cycling. Dwight ________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Bill Degnan via cctalk <cctalk@classiccmp.org> Sent: Monday, September 17, 2018 12:07:22 PM To: p.gebha...@ymail.com; General Discussion: On-Topic and Off-Topic Posts Subject: Re: Looking for two DEC H445 power bricks for PDP 11/40 project here is a photo of some of the failed regulators I have on hand that I have pulled from production over the years: https://pbs.twimg.com/media/DML8O8dW0AISX5m.jpg On Mon, Sep 17, 2018 at 3:05 PM Bill Degnan <billdeg...@gmail.com> wrote: > H745's are harder to find. I have at least one that needs service but I > am located in the USA and I have no clear idea what's wrong with it. Is it > that you have zero h745's at all or you have a bad one? Is there a typical > point of failure for these? If so, I'd try to track down a bad one and fix > it. Probably a lot cheaper. > b > > On Mon, Sep 17, 2018 at 2:54 PM P Gebhardt via cctalk < > cctalk@classiccmp.org> wrote: > >> Hello Noel, >> >> thanks for your quick reply. There are indeed some DEC power brick models >> on epay, but none regarding the H745. >> >> All the best, >> Pierre >> >> >> >> >> > From: Pierre Gebhardt >> >> > two H745 bricks (delivering -15V) which are still missing. I'd be >> very >> > happy, if anybody could consider parting with one or two. Location >> is >> > in Germany. >> >> There should be some on eBait; mildly expensive, but if you get them from >> the US, the shipping is going to be a fair amount anyway... >> >> Noel >> >
