820-00165 No video.

bjf

Member
Not a spill. EDP_PANEL_PWR is at 0V. Using a known-good test screen and DC-In board/cable. Fan spins, CPU is on. SMC_LID is at 3.4V. Any ideas for a next step?
 

2informaticos

Administrator
Staff member
USB mouse working?
Next check 3V presence at pins 18/19 of J8300 for at least 1-2 seconds.
In that short time DP_INT_HPD should go high; is a sign that eDP is correctly detected.
 

dukefawks

Administrator
Check EDP_PANEL_PWR when powering up. There will only be a pulse there if anything is wrong.

Caps present? C8320/21 and 24/25. PRAM reset done?
 

bjf

Member
Yep, not booting, trying to figure out why not. I put another board in the exact setup I'm using to make sure all the parts were working - screen, speakers, trackpad, trackpad cable, keyboard, screen, DC-In board and cable - to make sure my test rig was working properly. No chime.
 

dukefawks

Administrator
So at this point you are sure the board does not chime? Does it do a PRAM reset? Mouse light should go off during PRAM reset.
 

bjf

Member
To change only one variable (the board) I just now plugged everything in to my test board and did a PRAM reset. Mouse light goes off, speaker chimes. Then I switched out only the logic board and did another reset - no chime and mouse light stays on. I've noticed though that the board turns off for a second (fan stops) and restarts, almost like an 820-3437 board, but just one time, and then it stays on. This will happen no matter what is plugged in and whether or not I'm trying to do a PRAM reset.
 

bjf

Member
Everything checks out there. Resistors and lines are good. I checked the diode measurements on the SMC side of the resistors and they're similar to a good board. The board had a nice layer of untouched dust on it so I'm pretty confident there was no spill. Nothing looks damaged.
 

bjf

Member
No change with a known-good ROM chip on it. Computer still restarts about 8 seconds in. No chime.
 

bjf

Member
Ok, found that pin 7 voltage was low on ROM chip. Continuity was missing with R6131. Ran wire. Board chimes now, blinking folder and then dies about 10 seconds later. Still digging for more issues but haven't found anything yet.
 

bjf

Member
I hear you, but this board was spotless. I can't imagine any other way this could have happened besides a spill, but the board had zero signs of spill. I'm a little perplexed by this one. Either way, I'm treating it as some sort of spill and moving that way. I'll keep looking. If I'm measuring 3.4V at pin 8 of U1950 is that not evidence enough that it's good? Is there anything else that might be going wrong there despite measuring the correct voltage?
 

dukefawks

Administrator
Look at pin 8, is it corroded? Besides that it could be corrosion anywhere. Around U6100, clock chip, J6100, etc.
 
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