On Jun 15, 2014, at 08:49 , Toby Thain <toby at telegraphics.com.au> wrote: That's a pretty tempting solution. Those original bulbs are quite fragile, and appear to be quite prone to suffering lead breakage near the glass seal. Here's what I just posted on VCF, for those (few?) folks who are here but not there: -------- 8< cut here 8< -------- Regarding the console bulbs, I found that one of mine that snapped off at the base still has an intact filament. I was able to probe the wires at the glass seals to light it up and measure current. The bulbs are normally powered from an unregulated 14V rail as I understand things, and I measured the voltage at around 15V on my machine. The broken-off bulb draws 39mA at 14V and the filament color is quite orange. It draws 50mA at 28V and has a normal- looking color temperature. I conclude that the original bulbs were probably designed for 28V operation or so, and are used at lower voltage in the Nova 3 to increase service life (?). McMaster-Carr and Digi-Key both have some bulbs that look like possible substitutes. I think I'll try some 2185 bulbs from Digi- Key since I'm ordering other stuff from them anyway, unless anybody has a better confirmed cross-ref. Those are 28V 40mA bulbs. I also received an email from another collector who used KH 4-280-040A-1 bulbs from KH Lamp in his Nova. He reports that he got them from Swedish distributor Elfa as part number 33-657-98. That's a 28V 40mA T1-1/4 bulb.

Here's another testimonial for a Nova, this fellow mentions replacing them with 28V/0.04A bulbs, but doesn't say how he knows those specs: http://www.foxdata.com/blog/?tag=nova-312 The Hudson 2187D type he mentions maps to Chicago CM-2187, listed at Mouser: http://ca.mouser.com/ProductDetail/Chicago-Miniature/2187/? qs=qp111mKzDjgelZXllf1Wrw== And a datasheet listing: http://ca.mouser.com/catalog/catalogcad/646/131.pdf The datasheet is interesting as you can see how the lifetime and the light output (MSCP) tend to have an inverse relation on different lamp types with the same V/A specs. It may be if you select a type with too long a lifetime and then run it under-voltage to further extend the life it may end up being quite dim.

-----Oorspronkelijk bericht----- From: Toby Thain Sent: Sunday, June 15, 2014 5:49 PM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: DG Nova 3 Bulb Number? On 14/06/14 12:21 PM, Mark J. Blair wrote: Via email, snarfusmaximus writes, "I replaced mine with yellow LEDs with a series resistor." --Toby I do not have the schematic of the NOVA 3 console, but I seem to remember that the bulbs have a series-resistor to make some current flow through each bulb continuously. The current is low, so you do not see the filament glow. But when the full voltage (whatever that is) is applied, the bulbs lights up quicker because it is already "warmed". IIRC, this is also used in PDP-11/45 (and /70?) with bulbs, before the bulbs got replaced by LEDs (and the series-resistor was also removed). So, when you substitute the bulbs wth LEDs, you can remove that series-resistor. There is a website of a chap in Australia that did this and has a description of his "actions".

Although LEDs are certainly a lot easier and have longer lifetime, they are not a 100% replacement. Bulbs have a color temperature that is dependent on the current flow. Thus on a running computer, some lights seems more orange than others due to the duty cycle of the applied signal.

- Henk