[MelJon66]

Thanks again Chris,

Now that looks interesting as the converter might fit in the space above the transformer. There's a ridiculously large snap connector block in there but it may be movable. For my education how have you determined where to pick up the inputs to this converter?

Adding this converter is putting extra load on the q - r tapping so why is this better than just adding the +50v PSU to the o - p tapping which is at the correct voltage anyway? It must surely be more efficient that way as there must be some loss of efficiency in the converter.

Before the secondary failed I measured 56.3v ac at the m - n tapping while it was operating properly and +67.5v dc at pin 12, which seemed to make sense. I believe my DVM and the variac voltmeter both read RMS so when I connected the variac to pins 9 - 11 I was expecting to set it to around 56v, the same as the original transformer output. m - n and 9 - 11 are at the same ac potential, before rectification, so I still don't understand why that's not so. Putting 77v ac in to get 67.5v rectified dc out puzzles me.

Apologies for all the questions but I have a lot to learn.

Cheers
Mel