On Sun, 21 Feb 2016 20:09:47 +0100, Dimitrij Klingbeil wrote:

On 21.02.2016 18:27, Dimitrij Klingbeil wrote:
On 20.02.2016 15:36, JC wrote:
On 2/20/2016 7:55 AM, Cursitor Doom wrote:
On Sat, 20 Feb 2016 01:14:09 -0500, legg wrote:

Recheck pin function before jumping to conclusions.

Right; now re-checked. DC measurments proved (unsurprisingly) too
close together so I re-tested using 100khz instead. These are the
impedances WRT ground of the output taps of the long winding in the
order they actually come out of the transformer: GND, 0.17ohms,
0.17ohms, 0.26ohms, 0.28ohms, 3.7ohms, 3.8ohms. So this doesn't seem
to tally up with the schematic. Or does it? I need a pint of strong
coffee to kick-start my head on this one. :-/ Anyway, later...
... In one of your pictures there are a couple of diodes that look
messed up (V1809 and V1811) near the bridge. They are supposed to be
BY208-1000 (1000v rectifiers), I can see "40" on one, maybe 1N4007?

If you can't find a BY208-1000 replacement, a MUR4100E(G) should work.

Sorry, that may be physically too big to fit. A MUR1100EG or something
similar should work and fit in the available space too.

Dimitrij

Thank you. If you've had the chance to read my follow up to JC (I think
it was) then you'll be aware that one of those BY208 diodes was replaced
by a BY134. If the design is that critical of the speed of the diodes it
uses then maybe it won't function properly as you suggest. I can only
imagine the technician who replaced it was unaware of the critical nature
of the part concerned.
I'm kind of unhappy with this design overall, to be honest. It was
critically appraised on s.e.d and found generally unsatisfactory. I'm
strongly tempted to just save the transformers, junk everything else and
start afresh with a modern design. The rest of the scope is mint and
untouched, it's only the psu section that's been butchered around and
shows signs of burning and scorching in places. Maybe the best thing to
do would be to bin it? :-/