Panaplex display history

Johnny Billquist bqt at
Mon Jun 1 12:53:57 CDT 2015

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.


> 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.


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