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Old 11-01-2010, 10:16 PM  
PlainBill
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City & State: Phoenix, AZ
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Default Re: Can't seem to open Acer AL2416W case

Toasty is actually understating the case. An inverter is a constant-current high voltage source usually with over voltage and over current protection.

The circuitry usually senses the current through all CCFLs and adjusts the transformer drive to maintain the total design current through the CCFLs. (If a monitor has 4 CCFLs rated at 5mA each it will maintain 20 mA total current through the CCFLs.

Over voltage protection (OVP) shuts down the inverter if the voltage across any CCFL exceeds limits. Since current through a CCFL rises at end of life, Over current protection (OCP) shuts down the inverter if the current through any CCFL rises too high.

Essentially any anomaly will cause the inverter to shut down. Usually there is a 2 second delay from turn-on until it starts OVP and OCP is enabled.

I've marked up one of the photographs.

First step. I've numbered the pins on one of the transformers from 1 to 7. 1 is on the lower left corner, 6 is on the upper right, and is the output. Set your DMM on the 2K ohm scale and measure resistances from pin 6 to the other 5 pins (don't bother with pin 2). You should get a reading in the 1K range from pin 6 to only one other pin. This is the secondary winding. Now measure the resistance on the other 11 transformers. All should match to within 3%. If you find one that is outside this range, stop.

Next step. This test involves working with potentially lethal voltages. I suggest having an assistant. Note that I have labeled the lower end of C115 as Vsens. Hook up the boards in the normal working layout. Arrange it so your assistant can push the power button. Set the DMM to the 20VAC range. Now, probing from the bottom end of C115 to ground, try to get a voltage reading while the backlights are on. Repeat for C102, C137, etc.

Report your results.

Darn!! Can't find a datasheet for OZ9925GN.


PlainBill
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File Type: jpg Acer AL2416W inverter top-1.JPG (370.9 KB, 621 views)
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Last edited by PlainBill; 11-01-2010 at 10:21 PM..
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