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I have another 3476 Retina, had display and backlight... suddenly stopped. No voltage at connector (Bcklt or display). Does anyone have any tips? I also would like if anyone has known good, voltage drop values for pins.
TIA
My bad. Minor liquid damage, seemed to be concentrated around the battery connector, and the keyboard backlight connector. The components near the kb bl connector were fried, so I replaced them and it seemed to work. I put the board aside to begin on another, came back and it didn't work anymore. No BKLT voltage and no display voltage.
yes, yes, 0V at L8300... Tried working up the circuit. Led me to U8300, where its getting VCC but no outputs. Replaced... Nothing yet. Checked for short, .401 voltage drop.
Why did you replace it? Did you make sure there was an enable signal on R8319? I bet it's not there. Check L8300 again when you turn it on and see if you get a short "pulse" of 5V there, will be very short so hard to catch on multimeter, better with scope.
Also check SMC_LID first of course, must be high.
dukefawkslarossmann smc_lid is 3.40 out of machine, no 5v pulse, no en signal at r8319. Went up the circuitry, all resistors within spec. Could it be the cpu?
Definitely known good LCD. do you know what known good LED BKLT voltage drop should be on diode mode? If it's high what does that mean? Too high resistance somewhere correct?
dukefawks, U8300 change again, intermittent display/backlights. It seems like after a while u8300 is getting blown, but presently, I get a flicker on the LCD, but the weird part is I'm getting display and bcklt voltage even though it is showing nothing (no glow and no display). When I turn it on, it gives a brief glow and flicker of life though.