Searching for old DEC 12V frontpanel bulbs

just expect 12VDC I relamped the PDP-9 I am resoring for the Rhode Island Computer Museum a little over a year ago, and what follows is my description of that process. Given the time frame of the PDP-9, I suspect you're looking at a similar situation. I bought my 1764 lamps off the shelf from Mouser (www.mouser.com): The PDP-9 lamp board on which I wasted so much time and solder today is, I'm sorry to say, a nasty bit of work - not DEC's finest hour. Consider, it's 60 (not 56 as I previously reported) type 1762 T-1 3/4 wire-terminated lamps soldered into a board with 60 driver transistors, an electrolytic cap and a handful of connectors. It's buried deep inside the front panel, accessible, and only with difficulty, by climbing into the main system rack. Type 1762 lamps are very interesting. They're roughly 3/16" in diameter by 3/8" long, domed at the top (where they show through a masonite light blocker panel to the laminated plastic front panel of the -9), and roughly conical at the bottom. The wire leads protrude TO THE SIDES about 1/16" up from the bottom, and the leads are bent down so that they can be soldered into the board. I've seen oddball lamps before, but these are about as outr? as little incandescent lamps get. The wires are hard-drawn (ie: very brittle) copper, and they appear to poke through the glass without much of a seal. Over time the copper has corroded at the glass interface (Lots of green and blue ambergris. 'Looks good on an old roof, but is very disconcerting to see in electronic circuitry.), and the lamps break loose if you even think about looking at them. Also, enough tungsten has boiled off the filaments over the years that the top domes of most of the lamps are greatly darkened. I didn't bother to use any of the old lamps (although I salvaged what I could for posterity), but replaced all 60 of 'em with type 1764 lamps. Type 1762 lamps are damned-near impossible to find anymore (and given their construction I'm not surprised one bit); type 1764s are identical electrically (28V, 40ma, 340mA max cold surge current, CF-2 filament structure, 4000 hrs), and are the same size mechanically, but the wire leads come out the bottom through a more-conventional, and far less fragile, frit seal. Also, the leads appear to be tinned Kovar. They're stiffer but more malleable than the copper leads, they appear to "wet" where they seal with the glass, and they're magnetic. They also solder quite well. I dunno where DEC got those 1762s from. Maybe Ken got a good deal on 'em or something, and any insight from old DECies would be helpful here, too. But they sure did suck. In any event, all 60 lamps were removed. All 120 contacts (staked eyelets, by the way, pressed into a single-sided non-plated-through-hole tinned glass-epoxy board roughly 3" wide by 18" long) were cleaned - in large part to remove the drek left on the board from previous re-lampings. (I found evidence for at least one, and probably two, re-lampings, as well as the replacement of at least one of the driver transistors. One of the jobs was done by a tech whose training appears to have been at Hormel. He or she didn't know the difference between careful soldering and slaughtering hogs!) All 60 new lamps were installed and aligned (And I carefully made sure to get all their polarities right! <grin>), and the soldering job was inspected both visually under a magnifier and with an Ohm meter. The visual inspection found only one cold solder joint, and the meter found only one short (from a "sailor joint": gobs of solder), both of which were corrected. The driver transistors had previously been verified by junction checking. We should be set to go. I would recommend should a re-lamping ever again be required that LEDs rather than incandescent lamps be used. The availability of suitable lamps is questionable in the future (I just happened to find a stock of 300 at Mouser Electronics, now down to 250), and the ability of the lamp circuit board to take too many more re-lampings is questionable. A standard 20mA T-1 yellow LED (watch that polarity!) in series with a 680 Ohm 1/2W resistor to handle the roughly 15V drive voltage, "air-bridge" constructed to fit into the hole in the masonite light blocker of the front panel, would be a suitable permanent replacement for one of these lamps.