820-2914 no data or bklt

nate8organic

New member
got a 820-2914 with no data or bklt, chimes. shows dark screen under flashlight. lvds connector is good. getting power from the l9000. Had liquid damage. point in the right direction?
Thanks
Nate
 

dukefawks

Administrator
If L9000 has 3V something must happen to the LCD when you turn it on. Hold flashlight to the back of the Apple logo and then turn machine on.
What is voltage on backlight bus to connector?
 

nate8organic

New member
When i turn it on with the light of course from the back side of the apple logo. when i turn it on the screen reacts and makes the light become hard to see through the glass. if i turn it off i can see my light very well. this is the same thing im getting with the other board.

PPBUS_S0_LCDBKLT_PWR_SW im getting (-.08)v to (-1.5)v @ ppvout_s0_lcdbklt im getting (.2)v

also im getting solid 3.4v on the smc_lid
 
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nate8organic

New member
LCD_BKLT_EN = 3.2v so yes.

fuse was bad replaced it but no change

PPVOUT_S0_LCDBKL = 92.2 ohms to gnd on pin 40-38.
 

dukefawks

Administrator
So you replace the fuse while there is a semi short on the backlight bus? Resistance should be 150K+. Bad connector/lcd cable and dead fuse again probably.
 

nate8organic

New member
yeah okay i didnt realize that! haha lack there of knowledge = more work. :eek:

replaced the lvds connector and tried it on a second tested working screen and still the same. getting 90 ohms on the ppvout_s0. also double checked the fuse and it was still good.
 

dukefawks

Administrator
90 Ohm is coming from somewhere. Remove all components on the rails till the short is gone. Could also be in the board, usually at the LCD connector where it burns.
 

nate8organic

New member
okay. i removed D9701 and i was getting 120 ohms. like you said we need 150+ so i removed the xwd1150 and i got 250-350 ohms before it goes to saying 0 ohms. but if i replace these parts it goes back to 90 ohms so the short is in the line? what do i need to look for or do?
 

dukefawks

Administrator
I have no idea what you are doing. Remove D9701 and on pin 2 you should get 100K+. If lower than that there is a short on that rail.
 

nate8organic

New member
I had this board sitting to the side for a wile, just got back to it. if i remove d9701 i get 122k ohm on pin 2. what would i need to do to fix this semi short? sorry i dont know more to fix this entirely on my own, shorts really get me.
 

nate8organic

New member
343.9k ohms to ground on pin 1
122.2k ohms to gnd on pin 2
my meter does not have the right diode test mode its instead merged with the ohm reading, so im not sure how accurate it will be, but im getting 0.943k ohms one way and OL the other way.
 

nate8organic

New member
if i remove r9709 or r9708 the short goes away and i get 150k+ ohms at PPVOUT_S0_LCDBKLT. if i replace them there is no change and i did check the parts and i was getting proper ohms from them. if i pull the u9701 the short is still there so the problem is not in the u9701. where the heck could this short be coming from if it goes away on the bkl_fb by removing 9709 or 9708. either one removed eliminated the short.
 
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