820-2936 green light no power

[Jay]

This Mac draws 0.019-0.025 Amps at 16.5V
Green light on charger but no power. Does not respond to SMC reset.
In measuring rails I got to PP5V_S5 which fluctuated between 3.8 and 5V.
Replaced U7941 and U7200. Now a consistent 5V on PP5V_S5. Still no power though.
Moving down the rails I got no PP5V_SUS.
C1802 and C1803 3.3V
ADAPTER_EN at R5085 0V

Very small patches of corrosion were found on a few probe points in the machine but no corrosion was spotted on any components.

Where should I go from here?

 

[dukefawks]

PPBUS voltage? 60W charger or higher? ADAPTER_EN should of course be present.

 

[Jay]

PPBUS = 12.6V. Charger cable connected to bench PSU set to 16.5V 3.65A

 

[dukefawks]

It depends on what charger cable you are using. The ID is in the tip so if you use some 45W one from an air the board won't power on. Does it work from a charged battery?

 

[Jay]

Ah I see what you mean. I use 85W tips to use with the PSU. Only other battery I have is empty from a machine that "doesn't recognize battery" so hardly reliable. Tried it anyway, it's not charging as the Mac still only pulls about 0.020 Amps.

 

[dukefawks]

It will not charge as ADPATER_EN is not high. The machine is not seeing the adapter or there is something wrong with the SMC.

 

[Jay]

Reflowed the SMC, no change. Any other way to narrow down if this is the SMC at fault or something else?

 

[dukefawks]

I would first try if this boots from a battery with a charge. After that SMC change is next.