Several things come to mind.
LED's will make the problem worse.
Can you check to see if the bands are really 100 Hz just in case the
problem is something else?
For DC you could try a battery charger and auto lights (surely they are
less than $27)
I presume you have 220 VAC so watch out for high voltage but you could make
a simple 1/2 (or full) wave rectifier with a capacitor and run your $2
bulbs on DC. (watch out, the peak voltage will be higher than the RMS.)
Alex. F. Burr
In a message dated 5/13/2012 2:38:10 P.M. Mountain Daylight Time,
derek.chirnside@gmail.com writes:
Now, with an improved video camera (actually just my iPhone) the camera is
picking up scrolling bands across the display, I presume because of the
50Hz (as we have in NZ) voltage powering the bulbs, which I guess is making
100 Hz intensity variation.
I've thought of getting a DC setup, but bulbs cost much more. Like $27
rather than $2.
I've priced an LED option, this also is quite expensive, although there
are
other options I suspect.
Any thoughts? Is there maybe a simple way to phase shift the voltage
powering one of the bulbs? Or even do it to two other bulbs??