820-3315 - PP5v_s5 floating

[Palhano]

Line PP5v_S5 and PP3v3_S5 floating 0 to 3v, I looked for a short on the secondary lines, I did not find it. I tried to change the U7200, without success. It didn't work with SMC bypass, it didn't work!

Stable PPBus at 12.6v.
SMC_PM_G2_EN is floating

 

[2informaticos]

Any history available?
Did you test the board alone on the desk (nothing connected)?

Make short between pins 1 & 6 of Q7221.
Check if still pulsing.
If yes, try same trick with pins 3 & 4.

 

[Palhano]

No history. Some oxidation spots, which I've fixed and tested. Nothing line related.

Yes, I only tested the board.

With a short between 1 and 6, the PP5V stabilized.

 

[2informaticos]

3V3_S5 stable too?
3V3_SUS comes on also?

 

[Palhano]

Yes, the two stable lines with the jumper

 

[2informaticos]

Remove the jumper and R7978.
Check if L7260 gets steady 5V.

 

[Palhano]

I removed the jumper and the R7978.

PP5v_s5 floated again and the L7260 is 0v

 

[2informaticos]

Check R/C7260; also R7367/68.
Inspect all traces and solders around L/Q7260.

 

[Palhano]

I had already checked these components, all ok. The R7367/68 would be the R7267, right?

all ok L/Q7260.

 

[Palhano]

I found something strange! R7267/68 that I had tested, now they don't go up to the correct value. They stay at 5k, so replace both. They were OK, I put the charger to test, it didn't work. They went back to 5k.

 

[2informaticos]

The values measured onboard are not correct; normal behavior for high values.

Remove R7911/12/14 and test again the board.

 

[Palhano]

nothing friend!

I removed the components you mentioned and the same thing! this board is crazy!

When in doubt, I changed the R7267/68 or u7200 again

 

[2informaticos]

Did you remove all R7911/12/14/78?
L7260 doesn't even pulse?

 

[Palhano]

yes, I removed them all!

I have no pulse on the L7260

 

[2informaticos]

What is diode mode there?
Compare with good board.

 

[Palhano]

During testing, a short appeared on the U4800, but it wasn't the problem.

I compared in diode mode the L7260 (0.420) and the PP5v_s5 line as well (0.520), both equal to the good board.

I keep the R7911/12/14/78 outside, right?

 

[2informaticos]

Yes, without mentioned resistors L7260 should get stable voltage.
No other S3, or S0 power rails can be generated.
That's the reason I suspect a problem on U7200 and L/Q7260.
Just in case, change L7260 and Q7260/61.

 

[Palhano]

After changing Q7260/61, now I have stable 5v on PP5v_s5, L7260 and PP3v3_s5 line! But the board didn't turn on, is it because of the resistors I removed? Can I put it back?

 

[2informaticos]

Of course, put them back now.

 

[Palhano]

You are magic! Mac working again! Now I'm going to test!

thank you very much!