> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mouse > Sent: 20 December 2015 01:46 > To: cctalk@classiccmp.org > Subject: Re: VAX 4000-500 PSU Overload? > > >>> But getting something in series to measure load is going to be > >>> really awkward, [...] > >> As in, you don't have any such thing to put in series, or you don't > >> see a good way to get it in series? [...] > > I think the suggestion was to put an ammeter between the PSU and the > > backplane. > > Yes...but ammeters (for nontrivial currents) are generally just voltmeters > across current-sense resistors, and it's the current-sense resistor that needs > to carry the current and thus requires attention. >
The problem is just how to physically do it. But in any case I don't think it is necessary to do this now, as I have been able to reproduce the problem on the bench now. It looks like the 12V side starts up and then shuts down, sometimes after a few seconds, sometimes after a couple of minutes, sometimes it does not even start to output the right voltage. I am pretty sure that it is falsely detecting overcurrent. The problem is going to be finding and fixing the part that is not working, there are a lot of tiny surface mount components that seem to process the signal from the current sense resistor.... Regards Rob
