5 Apr
2003
5 Apr
'03
8:58 a.m.
So the object lesson here is that all switching
transistors are
not created equal, even in 1960's technology! Naturally since the
Having repaired (1960's) HP9100 calculators, I can agree with that. Some
of the transistors in there are critical. Very critical. The ROM address
drivers, for example (the main ROM is an inductive matrix...). And even
the EHT oscillator transistor is somewhat critical -- many of the obvious
choices for that one (like TV line output transistors -- HOTs to you)
will oscillate, but he voltage regulation loop doesn't work
-tony