A TUNE-UP FOR THE DUAL TURNTABLE - ThaiHDbox

PHOTO 5: The center hole cutter, which I built from a piece of brass tubing with a piece
of ¾� diameter brass rod for the mallet cap.
STROBOSCOPE LAMPS
Incandescent lamps (ordinary light
bulbs with a filament) work, but not
too well. The filament does not cool
very much between cycles of the AC
power so the light output is rather
constant. Fluorescent lamps are about
the same. The phosphor coating on
the inside of the tube continues to
radiate light between the AC power
cycles. You can see the stationary-
PHOTO 7A: The DIY multiple-LED
stroboscope lamp. The 14-LED array is
epoxied to the inside of the PacTec enclosure.
The four rubber feet (included
with the enclosure) ensure the LEDs do
not touch the tabletop.
appearing bars, but their edges look
fuzzy, so it’s difficult to set the speed
“right on.”
Neon lamps and white LEDs operating
on AC power work well because
both produce pulses of light even
though your eyes can’t really see the
pulses, at least not with 60Hz power.
You can use a neon “nightlight” (Photo
6), but it’s rather dim so it’s not too useful
unless the room is dark! Better lamps
20 audioXpress 12/10 www.audioXpress.com
PHOTO 6: An ordinary neon “night light”
makes a usable but dim stroboscope lamp.
are available.
For my use I built a multiple-LED
lamp (Photos 7A and 7B). A circuit
diagram with parts lists follows in Fig.
2. As you can see, the circuit is simple
and the wiring is not at all critical.
This lamp operates from a 12V AC
wall transformer and the “bars” are
much clearer than with an incandescent
light. The cost of the parts was
under $20.
PHOTO 7B: Inside view of the multiple-LED lamp. The male power connector mates
with the connector from the 12V AC wall transformer. The power on/off switch is optional
because you can unplug the lamp from the transformer.