Searching for old DEC 12V frontpanel bulbs

From: Pete Turnbull <>
Date: Mon Jan 28 15:46:35 2002

At 05:53 AM 1/28/02 -0800, Ethan wrote:

> I'm restoring some pre-TTL DEC stuff (R and W series logic) and I need
> a handful of front panel bulbs. Unlike the later bulbs with a plastic
> base and strong wires to solder to the PCB or to plug into socket pins,
> these are like a kernel of corn, with two fine wires coming out of the
> glass envelope at a slight angle with no supports of any kind.

Sounds like a standard T1_1/2 (about 3/16" diameter) or T1_3/4 (about 1/4"
diameter) wire-ended bulb. There are still a few companies that make them.

> If DEC was underfeeding these bulbs to extend their life, I would expect
> that the bulb should be rated at 14V-16V. I measured slightly over 12VDC
> in circuit, but well within a 5% tolerance.

The Farnell catalogue lists a few that are 14V. The correct bulbs for my
RL02 drives are 14V, fed from a 12V supply, as you say.

> I have checked the online manuals I could find, but no mention is made
> of the nature of the bulbs for 1966/1967-era DEC equipment. Any ideas?

Take a look at Farnell's online catalogue, at
and search for part number 328900. That should get a page with a small
picture; click on the image to get a table showing the charcteristics of
that family and a bigger picture
 Part number 3159346 will show you a different make (but only 12V). At
least you'll be able to see if that's the right shape/size and perhaps help
find a US manufacturer or supplier if you don't want to order from the UK.

BTW, if you try part number 316216 you'll find something like the bi-pin
ones for your PDP-8 panel.

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Mon Jan 28 2002 - 15:46:35 GMT

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