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pdp8e light bulbs

Roland Huisman

Roland Huisman

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Joined
Mar 24, 2011
Messages
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Location
The Netherlands
Hello everyone,

I've been reading on the web about the pdp machines.
It seems the PDP8e was made with old fashion bulbs and later the used LEDs.

Just wondering, when did Digital switch over to the LEDs?

Regards, Roland
 
Roland Huisman said:
Hello everyone,

Just wondering, when did Digital switch over to the LEDs?

Regards, Roland
Click to expand...

Only the first generation PDP-11 used incandescent lamps. The PDP-8 switched with the 8M
so around 1973. 5" peripheral indicator panels continued to be incandescent, though.
 
The PDP-11/05 front panel has LEDs. The earliest public announcement I'm aware of for the /05 is the OEM Price List dated April 1st, 1972.

Steve
 
Okay thank you all! I've seen a 8e which I can buy.
The machine seems to be dated in 74. So this one will
probably have LED's? Just very curious :D

Regards, Roland
 
Roland Huisman said:
Okay thank you all! I've seen a 8e which I can buy.
The machine seems to be dated in 74. So this one will
probably have LED's? Just very curious :D

Regards, Roland
Click to expand...

Only the 8M shipped with LEDs. If it has the original front panel board, and 8E or F will have bulbs.

I guess I only ever saw 11/55's and didn't realize the original 11/45 shipped with bulbs. That would
make sense since it shipped before the 11/05 or 40 in 1972.
 
Unless I'm misremembering, one of the undersung features of the 11/45 was a "bulb check" switch - one of the white "blank" keys on the front console could be flipped to check for burnt-out bulbs.

Jack
 
Hi All;
Jack, "" one of the undersung features of the 11/45 was a "bulb check" switch - one of the white "blank" keys on the front console could be flipped to check for burnt-out bulbs. ""
Yes, a "bulb check" switch.. Not a white switch, in mine, but a (I think) Red switch.. If You look at my early 11/45 video's, You will see me using that, for just that purpose.. Since I was putting in Led's, I needed to make sure the Led's were in the correct direction..
Maybe in later Versions of the 11/45 the switch was white, but mine was a colored switch.. And to me it was in the wrong position, when not being used.. But, I didn't design that Front Panel, or I would have put it in the other way around..

THANK YOU Marty
 
The bulbs in an 8/e are always on a little. That makes it easy to see if a bulb has failed, and actually makes them last longer.
In an 8/I you can reverse the power connections to the front panel and it will turn all of the bulbs on.
 
Marty said:
Hi All;
Jack, "" one of the undersung features of the 11/45 was a "bulb check" switch - one of the white "blank" keys on the front console could be flipped to check for burnt-out bulbs. ""
Yes, a "bulb check" switch.. Not a white switch, in mine, but a (I think) Red switch.. If You look at my early 11/45 video's, You will see me using that, for just that purpose.. Since I was putting in Led's, I needed to make sure the Led's were in the correct direction..
Maybe in later Versions of the 11/45 the switch was white, but mine was a colored switch.. And to me it was in the wrong position, when not being used.. But, I didn't design that Front Panel, or I would have put it in the other way around..

THANK YOU Marty
Click to expand...

on the 11/70 it's a white switch. And if its in the "wrong position" I think that you can just turn the plastic button arround.
 
Hello guys,

Recently I've picked up the PDP8/e. It seems to be quite an early one.
The machine was configured April 16 1971 according the label on the back side.
The M832 bus load PCB is dated Oct 28 1970. In the second half of the seventies
they upgraded the machine with extra boards and more memory. There are also several
wire wrapped boards in it. Original dec boards for user specific applications.

That M832 has a lot modifications on it. They even added a few components as a
modification which were connected by wires only.

M832 com side.jpg M832 detail.jpg wirewrap.jpg

Unfortunately the machine was upgraded with LEDS to work for ever.
As soon as I have the machine working again I would like to convert it back.
So I have to place all the resistors for the preheat current trough the bulbs
back in their places.

But I was wondering, how were these lamps placed on the PCB? I've found
some pictures and it looks like they are in sockets? The drilled holes in the PCB are
also quite big for just a bulb wire. Can anyone tell me how these lamps
were mounted on the pcb? It looks a bit like contacts from an IC socket.

bulbs 1.jpg bulbs 2.jpg
 
Last edited:
Hi All;
Roland, "" It looks a bit like contacts from an IC socket. "" Yes, Similar, basically a socket pin, with a slightly larger hole, for the Bulb wire leads.. That is what is in my PDP 11/45, where as I switched to Led's and plan to keep them that way..
But, I understand, you wanting to go back original..

How I envy You !!!

THANK YOU Marty
 
The only problem with LEDs is that it is difficult to tell if on LED is turned on more often than another LED. With bulbs the brightness depends on how often and how long they are turned on. This behavior is very useful for debugging.

The original sockets were probably AUGAT HOLETITE sockets. They are still available from TE Connectivity.
 
Thanks! Now I'm sure they were placed in sockets. Much better then soldered into the PCB.

That name HOLTITE brought me to this overview:
http://www.pdfdoc.ru/connectors/gen...onnections/contact-material-beryllium-copper/

This is much better then placing IC sockets! I will figure out which ones I need
and where I can buy them. What is the distance from PCB to lamp?
It looks to me about 5mm or 1/5 inch... Can anyone confirm that?

I found a replacement lamp CM7371 on : http://so-much-stuff.com/pdp8/repair/bulbs.php
12V instead of 10V (10V is obsolete) These lamps are already on my desk here...

Regards, Roland
 
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