CFL's: In-circuit testing with VOM?

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Old 02-01-14, 10:01 PM
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CFL's: In-circuit testing with VOM?

Greetings,

I have (15) 9-W CFL security lights of the 2-pin replaceable bulb type, installed in 2002. Over the years, as replacement becomes necessary, about half the failures are fixed by a simple bulb replacement, the other half being electronic ballast failure, requiring replacement of the entire fixture.

I've been accumulating these bad ballasts and now have (7), making it economically worthwhile to repair. Some research indicates the main electrolytic capacitor to be most often the culprit, followed by one or both transistors.

There is a fuse on the hot input to the ballast, which is good on all units, none of them show bad solder joints, burns, bulging capacitor, ie., nothing obvious.

With my electronics knowledge limited to Ohm's Law, and occasional soldering of small projects, I ask:

Do I need a VOM with capacitance feature to check for bad capacitor? Can this be done without de-soldering? What about testing components under power? (Yes, I know, this is risky, with several hundred volts on the secondary side of the transformer). I'm just thinking, all (7) units probably have the same failed component, if I can only discover it.
 
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Old 02-01-14, 11:17 PM
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You're trying to repair electronic ballasts ? Good luck.

Usually heat kills the ballast. That would point to a semiconductor failure.
More than likely the one or two transistors used as the choppers have failed.
 
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Old 02-02-14, 07:46 AM
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the other half being electronic ballast failure, requiring replacement of the entire fixture
You should not need to replace the entire fixture, you should just need to replace just the ballast.
 
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Old 02-04-14, 06:29 PM
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Thank you gentlemen, I should point out that these are not potted ballasts as are found in your typical fluorescent fixtures...these are out of Lights of America brand, model 9209, CFL's, whereby removing the back panel allows the ballast, which is a regular circuit board with a fuse, a 200V-6.8uF filter cap, (5)1N007 diodes, (6) resistors, a transformer, a choke (ferrite core) (2) 4124PC transistors, (5) film(?) caps, a varistor and an unknown component resembling a small filter cap with "15V" printed on it, to simply drop out, allowing the components to be easily de-soldered & replaced.

The manufacturer offers replacement bulbs, but not ballasts, as it is not a "user serviceable" part.
 
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Old 02-04-14, 06:33 PM
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(2) 4124PC transistors
That would be my guess and where I'd start. The biggest problem is trying to decode the part number to cross reference it for a replacement.
 
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