On 07/30/2017 10:59 AM, Ian Frost via cctalk wrote:
Any body any experience in fixing these old Acorn PSUs - or managed to source alternative modern supplies?
There wasn't anything "special" about them, in that the outputs were typical for "small computer with a hard disk" (i.e. +5V and +12V at a few amps, -5V and possibly -12V, main regulation done on the +5V rail, "hard start" via physical switch).
I expect it's possible to find a modern PC PSU in some kind of slimline form-factor which will physically fit (and rig the soft-start so that it powers up as soon as AC is applied). I expect the current limits for the different rails are printed on the side of the VMS PSU's frame, so as-good-or-better should be fine.
Unfortunately I did trace out some, possibly all, of that PSU (most likely, it was certainly a VMS-something in my ACW) years ago, but even if I do still have the schematics, they're on the other side of the Atlantic. The PSU in mine had the rectifier diode on the +12V rail go intermittent, so it would start sometimes and not others.
Tony D. might have schematics, but I have a feeling they weren't part of the ACW service manual as the PSU was bought in from an external supplier and not an Acorn part.
cheers Jules
