820-3437B not turning on

mushr00m

Member
Through Buzer Mode

R1931 communicates with R1800. However on the other side it goes directly to the CPU and I do not have any TP to check... It look likes it have a TP but it does NOT.

What to do now?
 

mushr00m

Member
CPU_VCCST_PWRGD = Tries to go to 1V and then back to 0V in a loop

Put back U1930 and now its the same behavior as above

Tries to go to 1V and then back to 0V in a loop
 
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2informaticos

Administrator
Staff member
PCH requires high level (1V) at CPU_VCCST_PWRGD and CPU_VR_READY, apart of 3V on pin 3/U1950.
If you get pulse on these, PLT_RESET_L should pulse too.
If not, check all voltages from page 11 (pulse at least); be sure all series resistors and coils are good there.
 
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mushr00m

Member
out of nowhere PLT_RSET_L appears
Then I had fan spin...
Then I tried to assemble
But I do not have external image.

This Macbook is without Backlight Driver and I will first make sure its working externally before putting a new backlight driver

This board had a lot of corrosion from being an old board.

After the fan is working and I do not have image.... it gets to spin in a faster while after some 30secs I guess
 
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2informaticos

Administrator
Staff member
If no LIO board, or trackpad connected, fan goes to max in 10-15s.

You should test the board alone on the desk for USB activity.
Also good to have a spare Air screen for test; I use broken one, to check backlight presence.
 

mushr00m

Member
PLT_RESET appears sometimes...

But not sure how to find which trace is bad and even if it's related to this guy or something before.

Can you help me with this board?

It has some corrosion since its and old board but I think its a board which have repair.
 

2informaticos

Administrator
Staff member
You didn't mention anything about advanced corrosion when started the thread.
SMC should be reballed in such case.
Passing board trough ultrasonic bath may help; especially in case of accumulated crap under CPU, RAM, or other BGAs.
Be aware, incorrect UC may damage more.
 

mushr00m

Member
I already reballed the SMC and didn't work
I do not have ultrasonic cleaner for this board =( What did was cleaning some pads which I tought had a bit of corrosion. It's not that bad but its what I think is making the board sometimes have PLT_RESET and even sometimes making it have fan spin working and after following as you requests.

What do you mean by UC?

After all our chat what would you consider and look with more care? RAM doesnt look bad to be honest
 

mushr00m

Member
I did it.

Some pictures for you to see what I was talking about "corrosion"

I would NOT consider it a not solvable solution BTW

and still same behavior.
 

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2informaticos

Administrator
Staff member
An ultrasonic cleaner (UC) may help, but not sure 100%.

There should be corroded components/solders, or traces.
 
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