On 2015-06-01 19:42, tony duell wrote:
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?
Looks nice in a dark room. :-)
And some of the lamps would flicker when the disk were busy, while
others reflected state.
The RL02 for instance. The LOAD button could be in or out. In addition
you had the lamp inside, which indicated if the drive was locked. You
could only open the lid when the lamp was on.
And when you pressed the LOAD button, that lamp went out, but the lamp
in the unit button only came on when the drive was up to speed and had
passed the initial head load. So button positions and lamps provided a
combination of indications and operational details.
On the RA8x drives, you have a write protect button, but the drive can
also become write protected through a software command, so the lamp can
go on with the button not pushed in.
But that don't really answer your question, as they could definitely
have placed the lamps separate from the buttons instead of putting them
inside. You could say that it was a space saving solution, but as you
have plenty of empty real estate on the front of the drive anyway, there
was no real need for this space saving.
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.
Yup.
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.
Right. I'm sure DEC *could* have done something clever. For some reason
they didn't. No idea why.
Johnny
