New subject: TRS-80 Model 16's looking for good home

24 Nov 2001

On Nov 24, 21:22, Ethan Dicks wrote:
...

 --- ajp166 &lt;ajp166(a)bellatlantic.net&gt; wrote:
 > From: Ben Franchuk &lt;bfranchuk(a)jetnet.ab.ca&gt;
 > >What about using white leds?
 > >Ben Franchuk.
 >
 > Why?  Back then when the led mod was common red was the only
 > available visible color for leds.  White leds are a bit blue rich though
...
  > they would work.  One point is that there are
some 28 or so leds/lamps
 > and good ones will not be cheap and cleap ones will not be good. 
Agreed.  The LEDS are water-white plastic, but red-emitting.  Each has its
leads cut short, about 1/8" from the body, and a small 430R resistor
soldered to the cathode and a wire (probably the trimmed-off resistor lead)
to the anode.  (Is this what some people have described as an "LED module"
or is that something more substantial?)  They then fit into the bi-pin lamp
sockets.  The resistors look like modern miniature metal film, but could be
20 years old.

Similar red LEDs cost pennies, maybe 10p.  25p - 35p with integral
resistor.  Bi-pin bulbs of about the right voltage/current/intensity cost a
bit more, about 50p each here.  I did think about white LEDs, but they cost
over ?3 each.  As Allison says, I would need 28 (plus a bag of spares if I
use lamps) and white LEDs give off a very cold bluish light, quite unlike
the slightly yellow lamps.  I thought about yellow LEDs, but they're much
*too* yellow. Then I thought about pairs of LEDs, but that's just getting
too silly.

...
  At about $3/each, yes they are expensive, but only
slightly more expensive
...
  than real DEC lamps.  Personally, I'd go with
either red LEDs or bulbs,
 since that's what's appropriate for the period. 
I think I'll stick with the existing LEDs and maybe "save up my pocket
money" to buy 40 or so bulbs (28 plus a dozen spares).

-- 
Pete						Peter Turnbull
						Network Manager
						University of York

PDP-8/E questions