No backlight display; what are possible causes

I've replaced a broken lcd on a working MBP A1226 twice with new display units. I currently use an external display as my monitor. Both replacement display units (clamshell) had the same problem of not having backlight on LED. I can shine a flashlight on the display to confirm that the LED is functioning properly.

Here are what has been suggested as possible causes of the issue:

1) Bad Inverter - could I have had two bad inverters in a row when purchased used displays that supposedly tested ok before shipping?

2) Bad Inverter cable - the backlight does not flicker on/off when wiggling the display. could I have had a bad inverter the first time and a bad cable this time?

3) Bad magsafe board - I bought this laptop with a bad display already. Maybe the magsafe board could have been damaged at the dc-in connector only. Everything else on the magsafe board works, including the sound, wifi and USB ports. The charger seems to also be working. The battery has a low cycle count and seems to charge fully do it does come down to 97-98% while plugged in on occasion.

I know this will be a process of elimination but wanted to see if there was anything I could do to test certain components before tearing into the laptop. Can I test the power on the pins coming out of the magsafe board to confirm the right current? If so, what should I measure?

Is there is anything I can try that is less invasive or can narrow my issue to a specific component or part?

I've reset the PRAM and SMC. I've tried it with battery power and with AC only. No change.

Thank you in advance for any information.

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You said you've replaced the LCD, are you talking about the screen or the whole top unit. You also stated "could I have had two bad inverters in a row" but do not mention replacing them. Please describe your efforts with the inverter.

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If you tested two known working complete LCD units on your machine and still have the same lightning problem then the logic board must be faulty, probably the electronic components located before the inverter socket on the logic board. A voltage reading at the inverter socket output could tell if there's voltage coming out of it.

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I bought a replacement magsafe board for my A1226. I was informed that it is common for the magsafe board to be the cause of backlight not working since it is powered from it. The logic board does not power the backlight, but powers the iSight camera which is working. I hope this will resolve the issue. I will update the post if this is the case or not after installing the new magsafe board (aka I/O board). Thank you for your assistance.

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http://www.rossmannsupply.com/blog/?p=32

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ramverma will be eternally grateful.
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