Frank I think we're getting closer on the diode mystery--the incircuit
voltage was 2.3-2.4volts when operating. Your chart indicated HZ2B1
limits are 1.9-2.1----diode marks appear to be 2-0B1 printed in black
ink around the radius of the zener. I substituted the old zener with a
5.1volt and the circuit did not like that at all--monitor lights dimmed
to the point where one couldnt read them. Didn't damage
anything--replaced old zener and ops went back as they were.
Thanks for the help