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Making a Flash Discharger
by Ben Vang
Camera Check Point, Dubbo NSW Australia
The flash capacitor discharger described here is very safe to use and has the added advantage of being capable of detecting current visually before discharge. We have used this discharger every day in our workshop since we first designed it in 1988 - we have not found a simpler and safer flash discharger anywhere.
The LED will light with a voltage from about 3v and up, and by always attaching the alligator clip to the Battery Minus side, you can 'poke' around without danger until you locate the 'HOT' spot (usually one side of the flash tube, but not always) before you press the discharge button.
Do remember to discharge 2 or 3 times after a little interval since the capacitor tends to reform and built up current again!
You need a push button switch capable of handling 3 amp, most standard switches are OK.
A diode bridge rectifier or 4 individual diodes (4002 or 4004 or similar, a 68K 0.5w resistor, a 500 mCd or similar bright Led, 2 x 100 ohm 5 watt resistors, a probe tip and a lead with alligator clip.
Construction is straight forward as per diagram below. I housed mine in a small UHF remote control box available from your local electronics supply store.
I strongly suggest you file a CROSS into the very tip of the probe. This prevents the probe tip from slipping when placed on a solder joint or other contact spot. Also remember to insulate the probe shaft right down to the tip.
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