820-3332 Intermittent power/green light

JohnB8812

New member
This one came in after a battery replacement claiming they have no power when the battery is plugged in, but intermittent power when the battery is unplugged. I can confirm this every other time I plug in the charger I get a green light and fan spin, but every other time I get no green light and no fan spin. PP3V42: 3.42 PPBUS: 12.28 volts. No power ever with battery plugged in. Is this a dead SMC or should I look elsewhere? Was liquid damage near the DC in port and fuse easy to scrub away with alcohol and toothbrush as no components were burned.
 

JohnB8812

New member
Also when I get green light and fan spin, PPBUS is literally zero volts. I have no idea how.
Check that 12.58 volts
 

JohnB8812

New member
Update, now it's magically working off the battery.... any insight is appreciated because idk what the fuck is going on with this lmao\

I got it to work a few times off the battery now it is not. I hate to keep spamming this, but I just want to give as much detail as possible
 

dukefawks

Administrator
SMC seems to be not starting all the time or the power button is putting it in bypass mode. Disconnect keyboard and try again, check SMC_RESET and SMC_ONOFF.
 

JohnB8812

New member
I measured originally without the keyboard attached. Without keyboard attached: SMC_RESET_L: 3.4 SMC_ONOFF_L: 3.4 volts. PPBUS gives me weird measurements too like 0.8 volts with a 3 Millionohms resistance to ground then once and a while 12.28 volts then when the board actually kicks on its 12.58 volts.
 

JohnB8812

New member
Ok will do when I get back tomorrow. Board looks really clean but kinda looks like it was Ultrasoniced previously. Would reflowing SMC be a good idea?
 

JohnB8812

New member
Ok so after reflow now I'm getting weird readings.

PP3V42: 3.42 volts
PPBUS_G3H: 0.35 volts
SYS_ONEWIRE: 0 volts
ADAPTER_SENSE: 0 volts
SMC_BCAC_OK: 0 volts

I get 3.42 volts on the SMBUS pins on the ISL
PPCHRG_DCIN: 18 volts
PP5v1 charger: 5.1 volts.

Is this an SMC issue or could this be an ISL issue? I just want to be sure before I go and replace the SMC. The computer was brought in with a knockoff charger btw, so I was curious from the start if it wasn't SMC related.
 

JohnB8812

New member
No corrosion around the SMC area btw that I could see was obvious

ISL area my bad. Current sense resistors for both charger and battery measure good
 
Last edited:

dukefawks

Administrator
First thing you need is green light. Seems like your ACOK is gone so that is where you should look first. The usual checks on U7000, ACIN, DCIN, resistance between pins 17/18 27/28. Make sure this stuff is discharged! That is why you are measuring a "short" which later is gone. This is a good way to fry stuff with charge left on PPBUS.
 

JohnB8812

New member
Ok will do. DC in when I measured at work was 18 volts. Will check ACIN and the resistance measurements when I get back to work Monday
 

JohnB8812

New member
DCIN: 18 volts
ACIN: 18 volts
Resistance between pins 17 and 18 is 4.2 ohms
Resistance between pins 27 and 28 is 21.2 ohms
 
Top