The chime has four small light
bulbs (#259, 6.3V, 1.7W peanut
style) wired in series. My original
plan was to replace them with LEDs
(as shown in the diagram), but I
missed the warm glow of the
It also occurred to me that I had
never replaced them in the 28 years
since we installed the chime, and
they were still working when I took
the chime down. Let’s see, that’s 29 *
365 24 = 254,040 hours of
Interestingly, when I checked the
original bulbs again during reassembly, they were all defective. I
suppose that the filaments were so
brittle that my disturbance shattered
If there was ever any doubt that
lowering the light bulb voltage
extends its life, here is the proof: 16 /
( 4 6. 3) 100 = 63.5% of the rated
voltage. I got four new bulbs, and I
have my nice glow back.
Well, there you have it. I enjoyed
refurbishing this old chime, as well as
documenting the process. I hope you
enjoyed reading about it, and
perhaps it may even inspire someone
to tackle a similar project.
I put together a small download
package which includes a short video
of the chime after refurbishment as
well as the firmware for the PIC.
The firmware for this project was
written in C, and since my other
projects were always done in
assembly, this was a first for me
The program is very simple and
well commented. NV
34 May 2017
FIGURE 7. New circuit board in assembly stand.
FIGURE 8. Bottom view of new circuit board.