On 2014 Jun 15, at 9:06 AM, Mark J. Blair wrote:
On Jun 15, 2014, at 08:49 , Toby Thain <toby at
telegraphics.com.au>
wrote:
Via email, snarfusmaximus writes, "I
replaced mine with yellow
LEDs with a series resistor."
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.
I've certainly seen other machines where front panel bulbs were being
run below spec voltage to increase their lifetime, I expect it was
quite common.
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.