Ralph Farr wrote in message ...
Hi all,
I have a quick question I was wondering if someone might be able to
answer. What is the standard light bulb number for the 5V lamps in a
Heathkit GC-1195/1197 clock. They are 5V miniature wedge type light
bulbs that are used for the display segments. I guess this could be a
proprietary Heathkit part, but I was hoping maybe someone had changed
these and maybe knew if there was a standard bulb equivalent (the
Heathkit part number is 412-621. Thanks and I do appreciate any help.

Ralph Farr

Hi Ralf,

I built one of those clocks a long time ago and it is currently
lounging on my "to play with" pile. It was a great conversation piece,
and always drew comments.

Those little bulbs are problematic. I've had the clock for years and
they get loose in the socket, or burn out at different times. I'm
planning on replacing them with high brightness L.E.D.'s. You could
measure the lamp voltage with the photocell light (I think I remember
the intensity increasing with room light) and calculate an appropriate
value of series resistance for the LED. Glue it into the segment,
wire it to the board with soldered connections and you are done for
probably a few decades. I did illuminate a segment red, and it looked
great (keep the LED at the back of the bulb hole so the segment can
spread the light). I'd love to see it in blue, but then you get pretty
expensive.

Illuminate a segment for yourself with a LED before you commit to
hacking it up. If you use multiple LEDs per segment, I'm sure you can
make the thing overly bright.

As I said, it is waiting for me to try and I have no final report. For
me, if it doesn't work out, I'll trash the clock anyway. I'm done
playing bulb-boy.

That clock used to throw off some warmth from the linear regulator.
This should save some power as well.

Now, if you could only add the "atomic clock" circuit so the thing
sets its own time on power outage...

Good Luck,

Jim