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820-00138 no backlight

A

andrew boren

Member
i checked every fuse i could see. but i have no backlight, from the diag i did on it, it looks like i dont have the keyboard or lcd backlight. so im looking for f7700 any idea where that is on this board? or where to look. the customer said he spilled some water on this but i see no signs of waterdamage anywhere, not even the indicator being red.
 
larossmann

larossmann

Administrator
Staff member
Check SMC_LID first! No diagram posted so you must use last year's and guess.Also what voltage is present on pin 1 of LCD connector when screen should be on? 0v, 12.6v, 19v, or 50v?
 
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andrew boren

Member
5v on pin one, which one is last years? sorry i only know them by the 820-xxxx currently, and that also rules out my fuse being blown..
 
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dukefawks

Administrator
You are probably measuring pin 40. 5V on pin 1 makes no sense. Look at 00138 diagram, need to know voltage on PPVOUT_S0_LCDBKLT
 
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andrew boren

Member
unless im compleatly reading the diagram wrong pin isnt pin 13, 16, 19, 22, 25-27, 31-41 all connected to ground. and should read 0.
 
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andrew boren

Member
ok that is so confusing, the schematic shows 40 pins. yet there is only 30. sorry about that. makes way more since once i noticed it didnt match up
1 0
2 0
3 5
4 4.98
5 3.33
6 3.03
7 3.03
8 0.29
9 0
10 1.66
11-27 0
28 5.01
29 5.01
30 5.02
 
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dukefawks

Administrator
Need to know if the fuse is good first. It will be in the backlight IC area, not hard to find.

Also the the backlight IC needs to "talk" to the LCD for it to turn on, make sure you have a known good test LCD for a 2015/16 machine. Other year LCDs will not work.
 
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andrew boren

Member
i know the lcd works as i do have picture. im having a hard time finding the backlight ic area. is there a number on the chip i can look for?
 
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