820-00165 - Charging and turning on on Bench PSU, but no light or voltages on Apple chargers

it-solve

Member
Hi folks,

I haven't seen this before. Had this with liquid damage, extensive but not much corrosion. Cleaned the liquid and ran it through UC. Full functionality seems to be restored.
Although when connected to my bench power supply with Magsafe2 cable, MacBook works and charges as expected. With the original brand new genuine 85W MagSafe, it won't turn on, and the light on the charger will blink green (seems like power cycles). The same phenomenon with 2 spare genuine chargers.

Tried 3 spare DCIN Boards and flex cables.

PPDCIN_G3H - 16.5V with Bench PSU - 3.3V with Genuine Chargers

The bizarre part is that with any of these chargers when connected to spare A1466 turns it on, but loses the backlight in 10 sec and keeps running.
While it seems to be ok with the bench PSU.
 

2informaticos

Administrator
Staff member
That happens because original Apple charger is SMART enough.
It has an embedded processor, which prevent delivering full voltage in case is not happy with connected Mac.
Magsafe 2 charger delivers only 3V, allowing just 100uA aprox.
Once the machine is properly detected (not overload, nor leakage), output voltage goes to its nominal value.

This behavior was already mentioned many times on the forum; just take notes, even from other members threads!

Q7180 is the first suspect here.
D7012 fails sometime too.

BTW, Magsafe 1 works in similar way, delivering 6V at first.
 

it-solve

Member
Thanks, @2informaticos, that was very helpful. I should go back and read as much as treads as possible.

Got it! R7180 was not measuring 100K due to corrosion destruction. Thanks for pointing into the inrush limiter.
 
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it-solve

Member
I come across another issue on this one. Everything works fine but there is no external display via the Display Port when the internal LCD is connected. When LCD is disconnected there is a greenish fuzzy picture,

20220606_095225.jpg

TBT_A_HPD - Goes 3.3V when TB connected
TBT_A_HV_EN - missing with connected or disconnected LCD
PP15V_TBT - missing with connected or disconnected LCD
 
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2informaticos

Administrator
Staff member
You should have a problem with U2800, or some corroded component/trace on its area.
Be sure no short to ground at D3095 (any pin).
 

it-solve

Member
I thought the same, but wasn't sure about reflowing it. Especially inside of that shield frame.
No Short to ground on D3095
 

it-solve

Member
Diode OK - Same reading as donor
When Ground on 2/R3081
P1/D3095 - 8.5V
P2/D3095 - 14.5V

Same greenish Display

When the ground is removed, Diode readings fall to 0V
 
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2informaticos

Administrator
Staff member
So U3090 boosts in this case.

Check all U2800 power rails (page 26).
If all good, should change it.

Just in case, replace first U3220 and be sure all around J3200 is OK.
 

it-solve

Member
Replaced U3220, no corrosion around/at J3200. UC must have cleaned it.

With Replaced U3220 I have lost video on external completely (Only Black Screen). Returned the chip back, but still no video. Perhaps heating in the area must have separated corroded U2800 balls.

Reflowed U2800 by removing the shield, and the video is back.

Thanks again @2informaticos
 
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