PDP-11/20, was Re: ebay question

From: Ethan Dicks <dickset_at_amanda.spole.gov>
Date: Thu Feb 26 08:26:52 2004

On Thu, Feb 26, 2004 at 08:23:46AM -0500, Robert Krten wrote:
> William Maddox sez...
> >
> > > PS. There is a NICE PDP-11 waiting to sold at VCM.
> >
> > If you compare the picture of this machine with with the 11/20 on
> > Guy Sotomayer's site, the front panel of the machine on VCM looks
> > like it has been (inexpertly) modified...
> >
> > Here is a picture of what I think a PDP-11/20 is supposed to look like,
> > with a smooth front panel surface like the PDP-8/L of similar vintage:
> >
> > http://www.shiresoft.com/pdp-11/inventory.html
> Well... other 11/20's look a little different :-) :-)
> http://www.parse.com/~museum/pdp11/index.html

Ruggedized machines aside, _my_ 11/20 looks like the one depicted at
shiresoft.com... smooth panel (with incandescent bulbs behind).

I can only guess that whoever modified that 11/20 did not have access
to bright-enough LEDs to leave them behind the panel, or didn't have
room to add current-limiting resistors between the plexi and the PCB.

I've had to recently manufacture an LED replacement bulb (for the HV ON
light of a LeCroy 1440 High Voltage "Mainframe")... The bulbs are GI 382s
marked "14V 80mA". We have three 1440s with two bulbs each, and *no*
good spares left. :-( I removed the glass envelope, found a tiny LED
(don't remember the T-designation, but the red epoxy envelope is under 2mm
long), and fit it and an SMT 103K resistor inside the body of the former
bulb so it all fit in the back of a lighted switch.

I'm thinking of a similar mod for my RL01s and RL02s when I get home. I'm
tired of burned out FAULT and LOAD lights. I'll probably save the bulbs
for the READY spot (since white LEDs are too blue to look right behind
a milky-white cover).

(who is still also looking for a decent replacement for PDP-8/S bulbs)

Ethan Dicks, A-130-S      Current South Pole Weather at 26-Feb-2004 14:20 Z
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Ethan.Dicks_at_amanda.spole.gov     http://penguincentral.com/penguincentral.html
Received on Thu Feb 26 2004 - 08:26:52 GMT

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