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[SOLVED]820-3330 - PPBUS_G3H at 1.18V

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smiba

smiba

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Hi,

I have a 820-3330-B here that came in with no green light on the charger and a PPBUS_G3H of 0V.

I replaced U7000 from a donor board and this brought back the green light (I also restored pin 11 as it was gone from the board). It still woudn't boot since PPBUS_G3H was way below 12V so I was under the impression that maybe it wasn't solidly soldered on. I heated it up again but this time while gently pressing down to make sure all the pins make good contact. This actually made the system boot again properly, but was rather unstable (Would power off after a few minutes of using).

After this I decided to get U7000 from another donor board because these boards come from who knows were. With this chip soldered on the system wouldn't boot and PPBUS_G3H was once again too low.

So I just bought a spool of these chips because they're not that expensive, however a new chip didn't resolve the issue either, PPBUS_G3H was still at 1.18V. The issue is probably with the circuit around it, not with the chip itself.

PPBUS_G3H is also not shorted to ground, removing the fuses still keeps PPBUS_G3H on almost the same voltage of 1.18V

Voltages:
(Using a original apple 85W charger.)

PP3V42_G3H = 3.43V (Pin 12/VHST on U7000)
PPBUS_G3H = 1.18V
PP5V1_CHGR_VDD = 5.4V (VDD & VDDP on U7000)

PPDCIN_S5_CHOP = 18.42V

CHGR_ACIN = 4.46V (Pin 3/ACIN on U7000)


Thanks in advance for the help again
 
smiba

smiba

New member
Pin 2 has a very unstable voltage between 3.3 and 5.2V

R7005 has 2.91Kohm resistance, the schematic tells me it should be "20"

Can you confirm R7005 is not within specification and the schematic is correct?
 
larossmann

larossmann

Administrator
Staff member
smiba said:
R7005 has 2.91Kohm resistance, the schematic tells me it should be "20"

Can you confirm R7005 is not within specification and the schematic is correct?
Click to expand...

If I told you a meal I were cooking contained 20 mg of cholesterol, but it actually had 2910 mg of cholesterol, how would your heart react to you finishing this meal? :)
 
larossmann

larossmann

Administrator
Staff member
Check for a short to ground on CHGR_DCIN before replacing R7005. A bad ISL(or a crappy charger) will blow R7005.
 
smiba

smiba

New member
I replaced R7005 after making sure there is no short on CHGR_DCIN, the value is now at a precise 20Ohm

Sadly it did not solve the full issue, PPBUS_G3H is now at 1.68V and as time progresses slowly drops lower. After 1 minute PPBUS_G3H is at 1.42V

I will check some of the other resistors around the area later today, but is it possible this is being caused by the two MOSFETS (Q7030 & Q7035)?
 
smiba

smiba

New member
R7022 and R7021 replaced because they were closed. Did not resolve issue

As final I decided to replace the ISL with another new one and the fans came back alive. Lets see if it will boot and stay on
 
smiba

smiba

New member
Yup, all good!

Unlucky combination of having a bad replacement ISL and also broken resistors, got it fixed

Thanks again Duke, Louis and aprendiz
 
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