820-3662-A PP20V_DCIN_FUSE low, dead laptop

[djdblaster]

Hello,

PP20V_DCIN_FUSE is 3.1V, F7005 is removed. Looking at schematics, I should get 20V here. Tried got known DCIN board, no change.

Am I missing something obvious?

 

[2informaticos]

If Apple original MagSafe2 charger doesn't detect any load, will not deliver more than 3V!!!
So, resolder F7005; charger needs to "see" R7012...

 

[djdblaster]

Okay, F7005 is back. Voltage jumps back and forth from 1.72V to 1.76V. Resistance on F7005 is 21.5kOhms.

 

[2informaticos]

Now post resistance to ground at PPBUS_G3H and 3V42 rails.

Your charger detects leakage and get protected.
Measure onboard R7180/81 and R7185/86.
This can discard a Q7180 issue...

 

[djdblaster]

3V42 - 90kOhms
PPBUS_G3H - 450kOhms

R7180/81 and R7185/86 all have correct values.

 

[2informaticos]

We normally check power rails on diode mode, red probe to ground.
Only switch to ohm scale for low values...

Post voltages on Q7010 area.
Be sure D7010 is not shorted.

 

[djdblaster]

Diode mode:
3V42 - 0.281V
PPBUS_G3H - 0.415V

D7010 is not shorted. Measures one way 0.745V, other way is OL.

Q7010 has 1.65V across all of it when charger connected. I feel like it could be shorted since C7012 beeps on continuity mode with D7105 on PPDCIN_G3H_ISOL.

 

[2informaticos]

If short/low value on D-S, charger will detect that as leakage.
Change Q7010 in this case.
I hope you checked that without charger connected...

You can use fake charger, or lab power supply to test; check if board starts.

 

[djdblaster]

I checked continuity without the charger connected.
I tried injecting 20V 2A on F7005 pin 2. It pulls 0.065mA. I don't have a fake charger at the moment. Does the original charger need to be connected while voltage is injected? I saw Louis do it once if I remember it correctly.

 

[2informaticos]

Why 20V?
16-18V is good enough.
Then check PPBUS_G3H and 3V42 rails.
Don't connect original charger, when lab power supply is used.

 

[djdblaster]

I didn't fiddle more with DCPS, rather, I replaced Q7010.

I get orange light now, PPBUS_G3H is 12.56V. Computer doesn't start yet. Doesn't it start automatically? I guess I'm missing some more rails.

 

[djdblaster]

I went through the list of rails and noticed PPVRTC_G3H is 2.7V instead of 3.42V.

Resistance to ground on PPVRTC_G3H is 36.5kOhms or 0.391V diode mode.

So to inspect that rail first?

 

[djdblaster]

So I have reflowed U1900 nice and easy since I thought it was not making a good contact. U1100 looked clean.

After reflow, I get 0 Ohms on PPVRTC_G3H... I've removed then U1900, still 0 Ohms...

 

[2informaticos]

There are some caps on that rail.
If still short after removed all, then bad PCH...

 

[djdblaster]

I’ve removed the caps too. Still 0 Ohms.

Prior to reflow, PPVRTC_G3H measured around 36kOhms. I didn’t connect any power after. Could PCH reflow help?

 

[2informaticos]

You cannot remove a "pure" (0 ohm) short with reflow.
Crap under PCH can pull down a signal, but it will have few kohm value to ground...
Be sure you didn't make any short between some pads, with the solder iron.

 

[djdblaster]

No short between pads. Simply PCH failed for some unknown reason. Can it be replaced?

 

[2informaticos]

I do not recommend to waste more time on this board.
Is the worst MLB Apple made ever.
CPU power supply is known for really strange issues...

 

[djdblaster]

Okay. Mark as solved then please.