Lou, Looks like you have friends on this reflector! The old Motorola HEP catalog from 1975 shows that the HEP R0052 was the substitute for the 1N458. That was their 200piv 1A silicon diode! At least that's something to try. It'll probably work whatever its function. Seriously, let us know what it does--I have a couple of SB200s myself. 73, Tony, N2UN