820-3332 power issues

[jgraffis]

Here's another fun one. 820-3332-A board this board had been brought in for beer spill. i get green light on charger but only had 1.7v on ppbus_g3h.Looked to be a problem with isl6259, i changed it out and got 12v back on ppbus_g3h. Plugged a battery in smelled something smoking, unplugged everything and ppbus_g3h is back to 1.5v.

Something seems to be shorting out the isl6259 when a battery is plugged in. i measured for short to ground on q7055, pin 5 gives me an 0L reading. checked for resistance on pin 5 with 0L still.

not really sure where to go with this one.

 

[dukefawks]

Need more info, a short on Q7055 does not tell me anything, how many pins does it have? The machine should have powered on without a battery too. I bet there is a short on PPBUS

 

[jgraffis]

q7055 has 8 pins 4 of which are input from battery as ppvbat_g3h. machine did not power up when connected to 85w charger. i show .427 in diode mode on F7040. But i just noticed that after i unplug the charger in diode mode it starts at -1.6 then goes to 0.427. so probably a weak short?

 

[dukefawks]

That is just capacitors on PPBUS discharging.

 

[jgraffis]

thats what i was thinking too. i did some poking around to find smc_reset_L at 3.3v. I'm missing a bunch of power rails. it doesn't get warm anywhere on the board so not sure what would be causing this.

 

[dukefawks]

PPBUS even present?

 

[jgraffis]

PPBUS_G3H is at 12.28v after i changed the isl6259 out for the second time. don't really want to plug in the battery and blow another isl6259 chip.

i noticed u7600pin 13 is at 0.012v with no short to ground.

 

[dukefawks]

12.28V is no good anyway, either SMC not running or SMC is dead. I bet dead SMC and dead battery.
Short on pin 13 is also no good, remove r7601 and check which side the short is coming from.

 

[jgraffis]

i have no way of check the battery really. but i checked and in diode mode on pin 13 of u7600 i get 0.374. maybe something went crazy and shorted some of the smc out. seems like i tend to get a lot of bad smc's. is that pretty common for water damaged machines?

 

[dukefawks]

Common on liquid damage and stuff that has been/is being fucked around with. If you have a green/orange light it should still power on though

 

[jgraffis]

yea i agree with you, I'm not questioning you... just new to this and not that great at reading the schematics yet. Sorry for the inconvenience.

 

[dukefawks]

3V present at L7260?

 

[jgraffis]

no voltage at L7260

 

[dukefawks]

Come one, engage your brain.......Voltage on PPBUS, R7940 and check short to GND on L7260. Green/orange light present?

 

[jgraffis]

ppbus_g3h is 12.28v. R7940 0.001v. in diode mode 0.5551. L7260 has a low diode mode measurement of 0.130. Yes i have a green light on the charger. i checked U7201 and it is receiving the 12.28v on vin but nothing on the enable signals.

 

[dukefawks]

Looks like at least a bad SMC to me.

 

[jgraffis]

found short to ground on pin 2 of d6950, tracked back to pin2 of r5281, removed r5281 and found short to ground on the pad going to the smc. I also found there to be a short on pin 1 of r5281 which i traced back to pin 1 of r6995. still not sure how this resistor could have a short to ground being that i removed u6990 to make sure it wasnt the problem. still dont understand how i had a green light with a short on pp3v42.

i dont have a replacement smc for this board. Thanks for all your help Duke.

 

[dukefawks]

No idea, inject voltage and see if SMC heats up. Pretty sure it will be dead, you will need a donor board.