Macbook 2009 820-2530 - no spin-up

[jpadie]

I was trying to solder back a broken speaker/mic connector last night and after finishing that job I found that the board would no longer power up. It's been a faithful companion to me since I bought it in 2009 so I would rather not give up on this one ...

All G3H rails are present save for PP18V5_G3H which is reading only 17.13v rather than the expected 18.5v. I'm not getting anything on the S5 rails.

I was using an iron only with the exception of maybe a few seconds of warmth (180C) to evaporate some alcohol.

If I had to guess, I'd say the culprit is U7200. Any thoughts on how to back up the guess or investigate other things?

 

[dukefawks]

PPBUS_G3H voltage? 3V3_S5?

 

[jpadie]

12.56v on ppbus g3h and 0v on sv3_s5

 

[dukefawks]

G2_EN present? If yes then check around the TPS51125, check for shorts on the outputs first.

 

[jpadie]

The en lines into u7200 were both at 3.3v. But the 5v outputs where at zero. I've taken it off the board for the time being.

will test g2_en in the morning. Thanks.

 

[dukefawks]

I hope you did not power the board without U7200 as this can totally fry everything!!!

 

[jpadie]

nope!

Replaced the chip this morning, and some resistors that blew off the board during removal. I didn't have the right value replacement for R7271. It's rated at 86.6k (1%) and may effectively create a voltage divider from the internal resistance to the drain of the n-channel mosfet (Q7221).

After replacing U7200 (tps51125), I've got the 5v rail back, the g3h lines are as above and the g2_en signal was 3.3v.

no spin-up still though! I didn't have time to probe further this morning but would appreciate any direction for next steps.

thanks
Justin

 

[JohnB8812]

Make sure you use the power on pads they don’t auto start this old

 

[jpadie]

Thanks John. Yes - not expecting modern magic! I was using the debug pads but nothing doing. Just in case I had the wrong pads, I reassembled the laptop but I'm still getting no spin-up.

I'd be really grateful for advice on what next to check.

 

[dukefawks]

Which 5V rail is back? Is there 3V on L7220 and 5V on L7260 when you power on?

 

[jpadie]

Parts now arrived for this and I have replaced u7200 with a new chip .

Still no spin up and I will test the power rails later. Getting a green light and I was getting the orange light. No longer but this could well be that the battery is charged .

I did notice that the battery indicator cable is shredded though. In two bits so no continuity on any pins. No shorts though (having unplugged it).

Is this indicator assembly critical to operation?

 

[dukefawks]

BIL is not needed. Orange light will not come on if 3v3_s5 is not present so I think you may have created an issue there.

 

[jpadie]

this board is back on the bench after the summer break. It's from my favourite workhorse of the last 9 years, so I'm keen to revive it.

brief recap:

board was working fine until I soldered the speakers back on to the board (the connector had ripped off years before). I must have knocked or damaged U7200.

New U7200 on the board (second new one, just in case).
PPBUS and PP3v42 are present
no s5 rails.

G2_en is at 3.4v.

5v3v3S5_reg3 is at 3.3v

5v3v3S5_reg5 is at 5v.​

15mv on L7220
8mv on L7260

on U7200 I get the following


1. 15mv
2. 15mv
3. 2.00v
4. 3.3v
5. 8mv
6. 0.75v

7. 13mv
8. 3.3v
9. 4.55v
10. 15mv
11. 15mv
12. 12.5mv

13. 3.37v
14. 2.0v
15. gnd
16. 12.57v
17. 5.01v
18.

19. 12mv
20. 10mv
21. 12mv
22. 4.55v
23. 10mv
24. 8mv

on Q7800 I have 3.4 at G2_EN (as above) and close to zero on PM_G2_P3V3S5_EN_L.

on Q7280 I get a few mv on 5v_s3_ll and pulsing from 300mv to 1.1v on 5v_s3_hh



all helpful pointers greatly appreciated! thanks
Justin

 

[2informaticos]

U7200 is correctly powered up and it has 3V3_S5 power supply enabled.
You should now have 3V3 at L7220.
If not, check for short/low resistance there.
Also check if C7220, R7269/70 are OK.

Don't forget to check all traces around U7200.

 

[jpadie]

yes - I do have 3v3 at L7220! and the 1v05 s5 rail as well. that's really odd: I could swear that they were not there when I last tested - I wonder whether the board needed to be turned on to have the s5 rails and somehow I failed to touch the contacts correctly?

anyway - great news. Now to find out why the s3 rails aren't present? It doesn't help that the schematic I have seems to be incorrect (no U7200 on it..., but it does have U7201).

On a related subject is there anyway to _guarantee_ that the right power up signal has been sent to this board? I don't think that there's any point in chasing the S3 rail without guaranteeing that the SMC is being properly told to start up.

Thanks!

 

[jpadie]

Hello no luck getting the s3 rails up. seemingly the 3v3 and 5v s3_en lines come from the MCP and neither are high. also PM_RSM_RST_L is not going low. any suggestions for getting over this next hurdle are very welcome.

 

[2informaticos]

Why would you want PM_RSMRST_L to go low?
How will then MCP work with active reset signal ???

This board doesn't turn on by itself; momentarly short power pads R5015/16.
Does the PM_PWRBTN_L react then?

 

[jpadie]

Thanks

I wrongly assumed that active low in this case meant that the signal would pulse low and reset the MCP for turning on.

The pwrbtn_l signal drops to 170mV or so when the pads are shorted.

 

[2informaticos]

So it drops 3V-0-3V?
That means SMC send the power button info to MCP.
This one should respond puting high the sleep signals, PM_SLP_Sx_L.
Look at page 66, Power Control Signals...

Do these signals pulse at least?

 

[jpadie]

I have not got an oscilloscope but on a multimeter the pmslps4l (which becomes p5vs3_en) stays low . This signal feeds the S3 en signal for the 3v3 rail too .

Bust mcp then.

Which is bizarre as all this happened when I was working on the audio connectors with the board disassembled .