Question about Canon Speedlite 420EX TTL Flash

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Just stopped. Batteries fine. No powering up sound. Not dropped, wet, etc. just quit.

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The xenon flash bulbs, capacitor, or small high-voltage transformer can go bad, and the unit will die. You can replace these components, but it's not easy or fun. You can ohm out the bulb and transformer to usually eliminate them, when change the cap first.
Make sure the battery contacts inside the unit are perfectly clean, and free of any battery chemical leakage or oxidation. You can use a qtip and alcohol, or fine grit emery cloth, if they're really bad.
Other than that, get the ohmmeter out. Make sure the flash capacitor (small, barrel shaped component) is totally discharged by shorting it out with a screwdriver, or other metal object. Short it out 3 times, just to be safe...about 5 seconds apart. The transformer and bulb should appear to be mostly shorted. In that case, try the cap. Then transformer, and lastly, the bulb.
Good luck, and hope this helps.

Posted on May 28, 2011


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