[SOLVED]820-3115 no green light but PPBUS and 3V42 present.

[JohnB8812]

This one has zero signs of liquid damage. PPBUS: 12.56 3V42: 3.42 volts. I checked both for shorts, but neither are shorted to ground. Tried known good DC in board and 85 watt no change. Q7080 has 18 volts on pins 1-3 and 4, so I assumed that might be the problem and replaced it. Still no change 18 volts on both gate and source. What do I check next? R7080 and R7081 measure correctly. This one I've been messing with for like 3 days so need help badly lol.

 

[JohnB8812]

Resistance to ground on pins 27 and 28 is 21.2 ohms pins 17 and 18 3.8 ohms on ISL6259

 

[dukefawks]

There should be no such resistance to GND and it would be impossible to have PPBUS, so I hope you measured between pins 27/28 17/18.

Simple green light issue....Known good magsafe board? ACOK present? Voltage on the adapter sense line?

 

[JohnB8812]

I do have 12.56 volts I could have measured wrong tho had many boards today. 3V42 is 3.42 volts, tried known good MagSafe does same thing as one with machine, ACOK is normal 3.3 and adapter sense is present.

 

[dukefawks]

So ADAPTER_SENSE and SYS_ONEWIRE are both 3.4V? If so then remove U6900 and do a diode mode check on SYS_ONEWIRE, SMC is now suspect.

 

[JohnB8812]

Ok will do when I get back to this one.

 

[JohnB8812]

Ok so yes adapter sense and sysonewire 3.4 volts. Removed U6900 and in diode mode I get OL or 6.1 kilohms

 

[JohnB8812]

*OL in ohms

 

[dukefawks]

Either a broken trace to the SMC or a dead SMC.

 

[JohnB8812]

Ewww wonderful lol. Will get back to this one once I get donors for it

 

[JohnB8812]

Ok resurrecting this one because finally got around to it. Replaced the SMC and now I have a power cycling issue.

PP3V42 stays at 3.48 volts and does not change
SMC_RESET_L stays at 3.3 volts and does not change.

However,

PPBUS pulses between 12.52 and 12.58
VRTC pulses between 3.2 and 3.4 over and over again.
PP5V_S5 pulses between 3.3 it seems and 0
PP3V3_S4 pulses between what seems to be 100 millivolts and 1.5 volts
PP5V_S3 pulses between 100 and 300 millivolts.

The only rail that is straight zero that I've checked is CPU VCore.

The green light intermittent as in it comes and goes out. Already replaced the clock chip.

Now that it power cycles, what could be causing it?

Current sensing circuit measures normal too in resistance mode.

 

[dukefawks]

Checked all rails for shorts to GND? ALL_SYS pulsing too?

 

[JohnB8812]

Have not will check in the morning when I get back to it and will check ALL SYS

 

[JohnB8812]

Ok so ALL_SYS stays pretty low. However, I think I have a short on PP5V_S3 resistance to ground is really low like 6 ohms to ground. I'll inject voltage and see what heats up. Is it safe to inject a lot of voltage into this line?

 

[JohnB8812]

Tried alcohol but can't find any heat. Going to get freeze spray it seems like injecting 5 volts at 1 amp nothing seems to get warm at all and the alcohol does bubble anywhere

 

[JohnB8812]

And quick question, is there any chance the TPS51125 could be causing this?

 

[dukefawks]

If you inject 5V there is 1A flowing. That means you are putting 5W into the board and something must absolutely get warm. Use face/lips for heat detection and expect to get burned

 

[JohnB8812]

Haha ok I'm gonna try again Monday I wanna fix this first time finally getting a SMC correct and it was so awful lol

 

[JohnB8812]

Found it! Put 5 volts and 3 amps through it and either C6214 or C6213 were shorted so pulled both and short is gone! Got to put a lot back, but I will test once everything is back on the board.

 

[JohnB8812]

FAN FUCKING SPIN BABY. Now going to test and see if it chimes and all that and run ASD. Light goes from green to orange with battery plugged in tho