> > Thinking about it, I find it surprising that on later disk drives -- RL's, > > RK07s, > > R80s etc, they used bulbs and not LEDs. By that date LEDs were easily > > available and > > reliable. > > I think it was just harder to replace the construction where you had > push buttons with lamps. Those are not bi-pins.
True. But there was no reason to introduce illuminated buttons, was there? The older drives had separate indicators. So DEC made a change which essentially forced them to use less reliable, higher current, indicators. IIRC the R80 (and probably others) has a lamp test facility so that when you get a FAULT you can be sure that the bulbs are all working and that the indication is therefore genuine. LEDs probably wouldn't have needed that. I seem to recall that CDC at about that time had a pushbutton with a rectangular LED on the surface of the button. That seemed quite a neat device. I am sure DEC could have come up with something. -tony
