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Anterweb

Anterweb

Member
Came in with liquid damage,

Coffee was spilt into the mac before christmas! It was pretty grim when I opened it up and it had 3 or 4 real bad spots of corrosion!,

Its had a good clean and after passing through the Ultrasonic the board looks like new again,

I get just 5v / 0 amps on USB-meter and I am reading a dead short to ground on anything related PPBUS_AON

( doing a visual inspection I cant see anything obviously wrong but do seem to have 2 missing components RC332 / CC332 - but unsure if this is one of those where the board dose not match the schematic but I do not have another same board to compare? )

Where to start finding this short? I'm a bit lost on these newer boards?

Thanks in advance
 
2informaticos

2informaticos

Administrator
Staff member
What is the exact ohm value of the short?
Check if any coil gives the same reading to ground.
If none bad, then you can use voltage injection method...
 
Anterweb

Anterweb

Member
OL would flash quickly on meter then go to 0.000

Just tried voltage injection and got nowhere, couldn't detect anything getting hot even with it pulling amps.
I think this one may be too far gone.
 
2informaticos

2informaticos

Administrator
Staff member
Use ohm scale, instead of diode mode, to measure the short.

If you really have pure short, then shouldn't have problems to find the culprit.
Set amp limit to max on the PSU first and start with 1V.
Be aware, even 1V may generate 10A (even more) into pure short.
5A PSU will not help at all.
 
Anterweb

Anterweb

Member
Found that cr637 was bad, removed it and now pulling 20v and charging the battery.

Still dosent turn on. Going over power rails I'm finding pp1v8_ is all short to ground.

Not site where to go form here?

Also can't find any power on pads for this do these macs have them?
 
Anterweb

Anterweb

Member
Sorry my bad,

pp1v8_AWAKE

Using this new meter that arrived today and its very different from my old one measures PP1V8_AWAKE = 009.5 ohm
 
Anterweb

Anterweb

Member
Its not recognized trying DFU , I do not seem to get any kind of power on state, no fan spin no trackpad.

I dont have another same board to comapre sadly
 
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