A few weeks ago i performed periodic maintenance on my Centurion. this
consists of blowing it out and swapping the tubes for spares to give them
some on time. One of the meter lamps was out. These are 14 v. 80 ma. rated
lamps as I recall. An exact replacement was unavailable at radio shack. I
could have ordered some by mail but I didn't want the amp sitting around
with the cover off--I wanted to get it back in service and not have to undo
everything a few days later to put in the lamp. I got the idea to try a
LED with a resistor to drop the v. down. It turned out radio shack had
LED/resistor packages, for example an amber one rated for 14 v. and 20 ma.
I didn't want to be real invasive about it, so I broke off the glass on the
burnt out lamp and soldered the LED package to the filament wires on the
base of the broken lamp and potted them with epoxy. After it dried, i
plugged the LED into the lamp socket, positioned it behind the meter, and
put everything back together.
It worked, but the amber LED is too dim to really make much difference
through the opaque scale plastic behind the meter arm. So the concept is
valid, but an extremely bright white LED is needed. I plan to keep working
on this the next time I have the Centurion cover off, because I'd rather go
the LED route than keep replacing those little incandescent bulbs.
rob / k5uj
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