I have posted here a couple of times because I have a failed VAXmate PSU. I have just posted a little bit more information here: https://robs-old-computers.com/2020/03/28/further-analysis-of-the-vaxmate-h7 270-psu-failure/ with some scope traces and a greatly improved schematic. Although the schematic is likely to have errors still. Unfortunately, a stray scope probe ground lead blew the fuse so now I have to wait for a new fuse to arrive before I can continue work.
I would really like to know if all the spiking I am seeing is to be expected, and any suggestions why it appears to be detecting an overcurrent? There do not appear to be any shorts on the secondary side, but that could be wrong of course. I don't know if a genuine short anywhere would cause it to trip the SCR quite so quickly (within 20ms of the switching transistor starting to switch). Any thoughts gratefully received. Thanks Rob
