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.
Some of the bulbs have burned-out filiaments. Many of the ones I need
to replace have broken wires externally. I am going to attempt to
solder new wires to the stub, but I don't expect the attempt to be an
overwhelming success. I might try a harder solder so that when I put
them back in the frontpanel PCB, they won't give way when I put enough
heat on the other end to install them.
About all I know about these bulbs is that they are fed a nominal 12VDC
from the W-series driver boards. The front panel itself is literally just
a PCB and a bunch of bulbs; no active circuits (unlike, say, the front
panel of a PDP-8/L). Testing should be easy - feed 12VDC at a few mA
to each set of fingers and check the bulbs, one by one.
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.
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?
-ethan
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Received on Mon Jan 28 2002 - 07:53:37 GMT