Now working!! Found a whisker across a track which was shorting the Zener and pulling down the 15V supply. Fitted a new Zener as a precaution. Now had control of the SCR's and assumed the SCR board was now good. Fitted Supplies Board and Control Amplifiers Board. Output V immediately went off the scale. Luckily the new uprated pass transistors survived, the old 2N3055's probably wouldn't have. Investigated the Control Amps board and finally found that the pass transistor driver VT2 (a 2n3253) was shorted, maybe because of the pass transistor blow up previously. I replaced it and now the supply seems to work with all original boards in it.
I am left with how to decide what the various set up pre set pots do, as the manual I have is for an earlier version with all discrete components, and the machine has IC's in some parts. I have schematics for both types, but the only manual I have and can find is for the early type boards machine.
On the Supplies board I know the pots are just volts and amps meter trim pots, and the set up pot for the over temp thermistor circuit.
I now just need to translate from the correct schematics and the incorrect (for an earlier, all discrete component supply version) manual, what the pots on the Control Amps board do.
So far I have, on the Control Amps board:
P1 sets max V output of the supply.
P2 sets max Amps output for the supply.
P3 ?
P4?
P5?
P6?
From the manual the older board had pots to also alter:
Short circuit protection set up
Mains voltage input variation
Separation voltage stability across the pass transistors
and other stuff. More pots than the 2 on the SCR board, more on the Control Amps board. The final thing is to try and translate waht the pots do and how to set them on these later boards... Can you tell from the schematic for the Control Amps board what any other than P1 and P2 might do please?
I have further annotated the Control Amps schematic to hopefully make it easier to follow. See attached please. Can't believe I finally have it working again after nearly giving up on it! Thank you.
Control Amps board schematic for the board in the PSU at
http://www.gatesgarth.com/H60002.jpgSchematics for earlier boards, to which the manual refers are at
http://www.gatesgarth.com/farnell_h60_50_early_schematics.pdfManual for earlier PSU with all discrete board components is at
http://www.gatesgarth.com/farnell_h60_50_0-60v_0-50a_power_supply_early_manual.pdfThanks to everyone for getting me to this excellent stage!!