Starting to look for the HP6268B power supply, no hurry. Could be a fixer upper as long as cosmetics are decent.
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It would be worth looking at the 6674A too.? The standard model is 60 V, 35 A, but there are options for 70 V 30 A (quite rare), as well as options for voyages lower than 60 V, but currents higher than 35 A. Those are switch-mode, but very heavy. They only run from 240 V or thereabouts power supplies - you can't use them on 120 V. There is no IEC connector - the mains has to e hard-wiresd in.