PDP8/e programmers consoles

[allison]

On 03/17/2018 09:09 AM, Noel Chiappa via cctalk wrote:
>     > From: Allison
>
>     > you have to pull the panel apart to replace them, gets tiring. Modern
>     > yellow LEDs are nice and bright, and don't burn out.
>     > Less digging in the box is a good thing as over time fumble errors can
>     > hurt it.
>
> Agree about replacing lamps - we switched to LEDs BITD because replacing
> burned-out lamps (especially when you're trying to fix some _other_ problem)
> when there's something better available is just, silly.
>
>     > Modern red leds at 8mA are very much brighter. However the yellow look
>     > more like lamps.
>
> What about warm white LEDs, though? The ones we used in the QSIC indicator
> panel are, to me, pretty much indistinguishable from the lights as I recall
> them from BITD. I mean, maybe if I had them sitting next to each other, I
> could tell, but... Those are SMD, though, but maybe they are available
> in bulb replacement form?
The yellow LEDs were fairly close to the bulbs as the bulbs are run at
lower
than rated voltage to improve their life.  The bulbs are not very white
as a
result.

I used a supply of dead bulbs to make mine. a little heat and the glass
goes,
a resistor and a 3mm led and good to go.   However the warming resistors
on the board need to be lifted (one end) or they never shut off.

White LEDs especially warm white were rather scarce and not cheap over
15 years ago so they weren't considered.  They would however make a
good choice with current high brightness parts.  Then there are all the
other colors now available I may do that in the future. 

For those that cringe about moding history...  I have three panels, the
original
lamp unit with lamps, A /M LED, and the one in the system moded for LEDs.
They serve as part of the spares collection and if I want to have the
machine
back to stock.


Allison

> 	Noel