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[SOLVED]820-3787 unstable S5 enables

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G.Beard

G.Beard

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820-3787 liquid damage, very recent no corrosion.

Customer says they heared a pop and that was it, no power.

All S5 fluctiuating.
P3V3S5_EN = On / Off
P5VS5_EN = On / Off

Schematic is leading me back to the SMC
 
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G.Beard

G.Beard

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PPBUS_G3H is 12V steady.
PP3V42 is steady 3.42

Tried injecting 3.3V into 3v3 and 5v S5 enables just to see what happens. Got 5V S5 rail but no 3V S5 and again, no S0... Thought it could be worth a shot but no cigar.
Removed the wire now.
 
G.Beard

G.Beard

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dukefawks said:
Resistance to GND on 3V3_S5 bus? Was there corrosion around U7501?
Click to expand...

What point should I measure from? EDIT: 3v3_s5 shows up all over. Not sure where you want me to take a measurement from.
Absoluetly no corrosion at all. spill only 2 weeks ago
 
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G.Beard

G.Beard

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From PP3V3_S5_REG to ground = ~ 16K
Just noticed that PP3V3_S5_SMC (connecting to SMC_WAKE_L through 1M R5002) = 1.2v .... This isn't right is it?

Sorry, feeling my way in the dark here
 
G.Beard

G.Beard

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aprendiz said:
Duke said 3V3_S5 bus not S3, measurement can be taken at any point where 3V3_S5 bus is present.....
Click to expand...

Sorry, typo I ment S5. I understand S5 is off state and S3 is one of the sleeps. S5 will be on while machine is off.... I just hit the wrong number key. Will have to be sure to read everything with care before I hit the post button.

Thanks

From PP3V3_S5_REG to ground = ~ 16K
 
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G.Beard

G.Beard

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dukefawks said:
PP3v3_s5_SMC should be 3.42V as it comes straight from 3V42 bus. So pin 1 of R5002 should have 3.42V
Click to expand...

Thank you for taking the time to reply to help

I was being a F* moron and probing the wrong point. 3V42 is good.

3v3_S5 and 5V_S5 both kick out the right voltage for a split second as the enable signal is sent from SMC but when injecting enable signals, only 5V_S0 turns on (tripple chacked I was probing the right point) so if 3v3_S5 was being pulled low for some reason then there would not be 3v3 at any point right.

There must be something telling the SMC to turn off the S5 enable surely?

I tried probing at U5110, U8130 in case they play any part.

Not a clue what's going on here... Not a F*ing danny
 
G.Beard

G.Beard

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I removed TPS51980 just to see what would happen to the enable signals. Signals are steady after removing the 51980 chip. Guessing something is turning on and telling the SMC to stop the enable signals.
 
G.Beard

G.Beard

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dukefawks said:
Replace it with a known good one now.
Click to expand...

Tried that, still the same thng... So then I removed Q8020 controlling PP3V3_SUS_FET rail and 3v3_S5 is stable. when Q8020 is on the board (or off) there is no power getting to the SPI ROM. I went through every single resistor and capacitor and IC removing systematically replacing everything on node 141 (or "short") in TestLink. I'll try removing Q8002 which controls the Q8020 gate just to see what happens.

I tried jumpering 3v42 over to SPI ROM VDD (which is on node 141) directly from PP3V42 but just ended in 3V42 pulled low and (obviously) no green / orange MagSafe.
 
D

dukefawks

Administrator
Isn't the board trying to power on and running into a short and shutting down? Are any of the S0 busses coming high for a second?
 
G.Beard

G.Beard

New member
dukefawks said:
Replace it with a known good one now.
Click to expand...

Tried that still the same thng...

I tried jumpering 3v42 over to SPI ROM VDD (which is on node 141) directly from PP3V42 but just ended in 3V42 pulled low and (obviously) no green / orange MagSafe.

So then I removed Q8020 controlling PP3V3_SUS_FET rail and 3v3_S5 directly from U7501 is stable. When Q8020 is on the board (or off the board) there is no power getting to the SPI ROM (pni 8 VDD on node 141). I'll try removing Q8002 which controls the Q8020 gate to see what happens.

I went through every single resistor and capacitor and IC systematically removing everything on node 141 testing 3v3_s5 & enables and then replacing the part. I did this to check for anything pulling that node low or maybe a bad cap but no joy.
 
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G.Beard

G.Beard

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I don't have any A143DJ mosfets or anything else in the right package so I've ordered in a batch from mouser.
Will have to wait a couple days to see if i makes any difference to replace them.
 
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D

dukefawks

Administrator
I have no idea what you are trying to do but did you check PP3V3SUS_EN comes high? If yes it should pull the gate of Q8020 to pretty much 0V.
 
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