Jim Attfield wrote:
... might know of a modern (or more importantly available) equivalent?
I can't find one in my books. It's a 3.5A controlled avalanche
rectifier diode, the 'controlled avalanche' bit is quite important as
they are from a switcher PSU.

Jim

Well, equally important is the voltage it's supposed to clamp. The only
one that comes to mind is an NTE570 which is used for 130 vdc. It's
designed to crater at 180 volts. If you know the voltage, you could use
a zener diode to achieve the same results if you can find one with that
current rating.