[turretslug]

The Motorola crowbar IC was probably the MC3423- I acquired a few from a big work-place clear-out long ago (wasn't the inefficiency and management change in British industry occasionally useful, ill wind and all that....) As David says, very simple to make a safety crowbar and if you want further sophistication, the application note is your oyster. It can be made into a postage-stamp matrix-board module light enough to be mounted by its thyristor tab- small enough for a 16V one to go inside my FRG-100 (very low down on the true enthusiast's pecking-order of radios, but expensive and useful enough to me!) and a 19V one inside the TF2002B (worryingly generous regulator headroom, besides I'd sorted out about a dozen different faults on acquisition and didn't want to spend any more time than I could avoid in its innards!)

Colin