Something similar to that works great for checking fluorescent ballasts
in games. Take a 60-100 watt bulb and connect it in place of the
fluorescent bulb (so you have the power going to the ballast in series
with the test bulb). The test bulb should light at less than full
brightness. No light can mean an open ballast, bright light means
shorted ballast.
Fun fact, the fluorescent bulbs in games run with 400 mA of current
through them. Small bulbs (5/8" like used in Eight Ball Deluxe pinball)
are around 250 mA. In an emergency a ballast may be replaced with a 75
watt bulb (for 1 to 1.5" diameter bulbs less than 25" long) or a 40 watt
bulb for the 5/8" diameter bulbs. Anything over about 24" uses an
autotransformer ballast and can't be operated with the substitute. The
light bulb, not being inductive, doesn't start the fluorescent as
easily, but will work.
(And now you know what I fiddled around with as a teenager!)
John Robertson wrote:
> Testing the Vector monitors with the yoke unplugged is like running an
> audio amp with the speakers unplugged. No load means little if any
> risk to the output devices if there is no input.
>
> If you have a scope you can hook it up across the yoke lines to see
> the results, if not, use a 15 watt 115VAC light bulb...the bulb will
> glow brighter (if no input to the monitor) if one of the output
> transistors is shorted. The bulb will not pass much current (whats
> 15/115V = X/60V? about 7 watts or 100MA - please check my math, but it
> is pretty low current!) - need my ohm's wheel to figure that out..
>
> I've used the light bulb test on my servicing of jukebox audio amps
> over the years (25) and no damage to output transistors, you can check
> that the amp is set up correctly and the lamp gives an instant
> indication of problems...with no smoke!
>
> John :-#)#
>
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Received on Sat Jul 6 22:51:43 2002
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