On 13 mayo, 13:53, who where wrote:

The switcher is cycling presumably due to an overloaded/short-circuited
secondary load. Without being able to see the feedback part of the schematic
but assuming it is from the B+ output, I'd lift D812 first and then D813,
checking whether the switcher recovers normal operation. If it doesn't - and I
expect it won't - then your fault lies in something hanging off the B+ line.

The psu stops its cyling/tweeting when the 123v line is isolated, but
still does not reach over 50v on that pin, which led me to suspect
some regulation problem. Not only that, but the line stage seems fine:
I'm using a bulb in place of the transistor, and I have not found any
shorts on the line transformer secondary loads.

I'm beginning to suspect the replacement line transformer may not be
correct. the original was an 1142.5057 but I was sold an ELDOR
1142.5077 (which , it says on the box, will sub. a .5057 or 30473 -
This may not be the case! Will contact them and check.

..