How to test a backlight transformer?

dmhines · Post by **dmhines** » Thu Jun 14, 2007 9:26 pm

Is there a way to test a backlight transformer (in a 15-2116) using a digital multimeter? My backlight quit working and if possible I would like to determine if it's the transformer or the EL sheet.

I've opened the case and found the transformer firmly glued in place and the solder points look good on the board.

Thanks.

zaphod7501 · Post by **zaphod7501** » Fri Jun 15, 2007 6:38 am

Not real sure about methods, but: the inverter is probably a DC -> AC converter putting out 100 - 400 volts AC at high frequencies. Your meter may or may not read well at frequencies over 60hz. The output will be in the kilohertz range. Static measurements (DC and Ohms) won't mean much without a working unit as reference and you'd probably have to remove the Xfmr to measure Ohms anyway.

Note: static testing is "one way". If a test indicates "bad", then it's probably bad. If a test indicates "good" then you don't really know much at all. ie, you can test for bad but you can't test for good.

You might be able to hear the whine of the circuitry, which would give some idea if the circuit is attempting to run. You might be able to measure the output of the transformer if you rig up some way to extend test points outside of the case but be aware that you can get a nasty buzz off of an inverter supply.