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820-3115 backlight, no display, no keyboard no trackpad, external display good

G

grmacs

Member
So this mac had no display at all.
Had a nest of insect garbage under board below cpu.

suspecting lid closed issue discovered R5075 for smc_lid was corroded and replaced along with C4920 and c4904 which were also corroded and coming off board.

NOw I get backlight (no image) and keyboard until boot. I can do pram for 1 chime then I believe the keyboard is turning off and after boot no keyboard or trackpad again.

What in boot cycle would kick on that might supercede keyboard and controller? I reflowed the SMC also. Also noticed if I leave the external display kicked in with lid open it doesn't turn the backlight or display on at all.
 
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G

grmacs

Member
CHanged out U5701. Get display not sure related to the U5701 but progress... Still no keyboard or trackpad. I don't think I was gettting any keyboard action prior looking back. I think I happened to have a smc lid issue AND apparently also a keyboard/tp issue.
 
G

grmacs

Member
SHould I have voltage at U5805 without keyboard/tp connected? I have 5V at pin 2 and nothing at the rest... I did try replacing U5805 already.
 
G

grmacs

Member
No click either. SMC reset works so there's definitely proper connection there but as soon as I hit the power button the keyboard must turn off, it won't do PRAM reset or go to bootable drive selection screen with option key hold, etc...

I do get proper 3.3V at two points of u5701 and at 3.42V and 3.3V on tpad and kb connectors appropriately. 18.5V with cables plugged in at pin 21 j5800
 
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G

grmacs

Member
Circling back to some of my older projects again...
Yes, 0V at pin 53 with kb and tp connected.
Power button works before and after boot. I tried changing the firmware chip for entertainment. NO changes regardelss of anything I've tried. Moved it to completely different TP/KB and nada. I was able to do PRAM reset with external but can't detect keys are registering other than the power key.
 
2informaticos

2informaticos

Administrator
Staff member
PRAM reset, also SMC reset, are done by hardware; corresponding keys go directly to specific chip (U5750).
For normal use, keyboard information (trackpad too), is decoded into U5701 and sent to PCH via USB.
You may have a problem with U2700 (USB Hub); check its area.
 
G

grmacs

Member
swapped out U2700 and tried swapping u5701 again to no avail. THinking I should just toss it into the parts bin unless you have any thoughts. I checked traces from keyboard to u5701 to u2700. I don't get it. PCH?
 
G

grmacs

Member
My external keyboard quit working. NOt sure if something with this machine caused that? The mouse hooked to keyboard still works. Using wireless w USB works. Maybe it just coincidentally quit.

No bluetooth.
 
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