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820-00840-A

Anterweb

Anterweb

Member
Don't have any history on this but was brought in with "Not turning on"

Upon removing the back case it looks like someone has removed the logic board and or the screen but no signs of any work to the logic board at all it looks like new with no signs or liquid damage anywhere on the logic or case.

It draws 20v and appears to be charging the battery.


00840.jpg

When first connecting battery and or charger I get a flash of light on USB stick then nothing, fan spins for a couple of seconds then nothing but CPU slowly getting warm .
( No power and no image on internal or external )

checking big coils I can find

12v
5v
3.3v
1.2v
All present

Tried logicboard in a known good case to eliminate screen/ keyboard/trackpad battery etc. same results.

I cant find any shorts, Medusa can see and read the bios fine., Bit stuck on where to go with this, any advice please?
 
2informaticos

2informaticos

Administrator
Staff member
CPU core voltage present?
Did you try known good BIOS?

If board was already removed by someone else, check for knocked off components, or broken traces.
 
Anterweb

Anterweb

Member
I dont seem to be able to locate the board-view and schem for this 00840-A are we using the 00875 set?

Not sure if this is correct but can I check for CPU core on L7210 + L7220? if so im getting (.957v) on those and the caps that leave them going to the CPU,

I do not have a good bios for this board to try but I have one for the 00875 that you sent me a while back can I use that?

Also, If I copy the serial from this mac into the Medusa will it still hold that serial to put back later if I upload a new bios to the medusa? or once I upload a new bios to the medusa will it loose that stored serial?

Checking for knocked off components and any bad trace was my first call under the scope, Looks perfect, I have a feeling they may have just replaced the screen .
 
Last edited:
Anterweb

Anterweb

Member
Just gave the bios a go and exactly the same behavior,
USB light blinks once, fan spin for 3 or 4 seconds and trackpad click, nothing else,

I did just notice that the trackpad stays " Clickable" for around 8 seconds then stops been responsive for about 4 seconds then becomes active again and repeats,, Like it's power cycling?
 
Anterweb

Anterweb

Member
PLT_RESET_L comes high? Yes 3.30v when it power cycles on, Its still doing 8 seconds on 4 seconds off,

( When measuring this i measured on R2013, Whilst doing so R2013 pinged off the board, hardly any pressure from my needle tip multi meter probes, Whilst grabbing a replacement R2013 from a donor board I notice that the fan is now spinning each time it power cycles on 4 sec on 4 sec off.,. (( It wasnt doing this before, Id just get a 4 sec fan spin then nothing from the fan unless I removed all power batt and charger then re applied it would spin for 4 sec then nothing at all. )) I replaced R2013 and it goes back to no fan spin when it power cycles just the one 4 sec spin when power first applied,

I also noticed that when it's been on a while cpu gets warm but I also notice that L7030 is getting HOT! and it lookskinda strange with a white ring on it, see pic.
ring.jpg

It feels like this is trying it's best to start but I'm missing something daft here.
 
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