Hey Guys,
Im looking for a bit of help in regards of finding a source for replacing a faulty backlight inverter board and have not been having any luck in locating the item I'm after on any of the main sources; eBay etc. I'm looking for a source to buy off of in context of obtaining a new inverter for my macbook Air.
Help is appreciated, thank you in advance for contributing.
SPECS:
MOD. Mid 2013 13' MacbookAir (A1466) 1.3 GhZ
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Inverters are for CCFL backlit LCDs which have not been used for over six years now.
To copy and paste from previous post of mine
Most "common" problem with no backlight is ball A5 on LP8550 or LCD connector, but guessing is BS and should not be done here.
put multimeter in diode mode, red probe on ground, black probe on pins 3/4 of LCD connector.
- 0.0 or 0.007 means direct short to ground, usually inside LCD connector or LCD cable.
- 0.200-0.300 is bad LED driver.
- 0.459-0.511 is bad feedback via or corroded away feedback ball under LP8550
- 0.565 is corroded solder ball or bad switch trace inside LP8550
Measure voltage along each point in the circuit. Before F9700, after F9700. At output.
At backlight output, measured on pin 3 or 4 of the LCD connector,
- 0v means short to ground, blown fuse, or no LCD conected. Check that you see an image on the LCD, check backlight fuse, check board via from FET after fuse to boost coil.
- 8v means no short to ground, good fuse, but no boosting. Check BKL_EN is 2.7 to 3v at voltage divider going to enable pin of WLED driver, check BKL_PWM signal exists.
- 27v or higher means all good, but your LCD cable or LCD backlight itself is blown.
If you see power along the line, where is it? Where does it stop?
If you replace a fuse with a short to ground anywhere in the line you have wasted your time, and a precious little 0603 package. :(
Lastly if it worked for a few months and then died most likely your problem is on bad feedback via/ball on LP8550, pins 3/4 coming corroded on LCD connector, or BKL_EN voltage divider resistors in that order.
Have fun!
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zzz, would you mind expanding your profile? Your answers are usually very good and you have a lot of board level expertise, I suspect you have been watching Louis's videos ;-)
I charge an extra 20% on average for machines that have been "repaired" before they get to me ;-) and consider that cheap at twice the price.
zzz, after re-reading your excellent posts I got a smile, you have watched The Rossman videos.
Louis alias zzz had a great sense of humour even back in 2015 didn't he :)
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do i replace the fuse before checking the voltage and to find shorts? ( i mean without turning it on) . can i use a polyswitch fuse jsut for the checkout?
If i have a short in my connector or cable, how do i check that?
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0if you replace the fuse without checking the backlight output circuit you risk blowing it again. PPBUS_G3H 8.6v will pass through the fuse and if there is a short between F7000 and and pins 3,4 of LCD connector then its a waste of a fuse as well as a possible blown LP8550
Listen to zzz and check diode on backlight output first.
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