Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

[platinumsteel]

Hi gooday again guys I have a situation am not to sure about hoping you guys can guide me further.Macbook Pro 2012 820-3115-B .Came to me with a fair amount of water damage all over the board.. Intermittent green light.No fan spin.It draws 0.13 amps on my bench PSU.Took pictures of all corroded areas and then I cleaned it to the best I could using alcohol. .Ended up getting it to power on and fan spin for like 3 times randomly. But really it still stays at 0.13 amps most of the time. I ended up changing 1 other corroded cap and a bad resistor but still no fan spin.I checked all resistors around U7000 ISL chip and all is well there.After slowly scanning the board for any visual signs under microscope.I found a cap (C1747) on PP1V5_S3RS0 .That was corroded badly. It is directly under the CPU..i removed it cleaned it's pad...and replaced it because i have an identical donor board.But when i removed it i realized that on pin1 it is shorted. On the 3 other identical donor boards I have that rail is not supposed to be shorted. As you can see in the picture that is the entire rail that is shorted.All 21 caps there and the diode beeps both sides.Can you guys tell me how i can determine if the CPU is shorted or maybe i can find the shorted cap? I think i can inject 1V there but really wanted to be sure from you all..Help will be greatly appreciated. I have all the tools required. Thanks in advance



List of voltage measurements
PPBUS_G3H =12.53V
PPBUS_S5_HS_COMPUTING_ISNS = 12.53V
PPBUS_S5_HS_OTHER_ISNS = 12.53v
PPDCIN_G3H = 18.5V
PP3V42_G3H = 3.4V
PPVRTC_G3H = 3.3v

PP3V3_S5 = 3.3V
PP3V3_SUS = 3.3V
PP3V3_S4 = 3.3V
PP3V3_S0 = 3.3V

PP5V_S5 = 5V
PP5V_SUS = 5V
PP5V_S0 = 5V

Drawing 0.13 amps

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

What is the resistance reading for that rail to ground?

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

What is the resistance reading for that rail to ground?

0.4 ohms

On good donor board
164.7 ohms

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Yes, I do believe that you have a shorted cap on this leg. However, suggest for a more experienced tech to chime in and confirm the same conclusion.

Our a1466 had a value of 0.2 ohms on the ppbus_g3h line.

We applied alcohol on a group of caps and injected 0.9v ar 30A (sunshine ts-30a) and one tantalum kept evaporating the alcohol very quickly with a small puff of smoke. Did this 2 times, same cap. Removed the cap and the macbook powered up and booted normally.

Do you have a thermal camera? We are in the market for a good thermal camera at a fair cost.

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

I just wanted to report back on some news on this macbook pro.I got frustrated and decided to just take out all 22 caps on that rail. Really wasn't in the mood to take out one by one and check for when the short was gone.So took out 18 of them and the short was still there.The last 4 took them out and short was gone.So it's either C1755 or C1752 . One of them was looking burnt underneath the Cap itself. So replaced it and put back all caps respectively .So yeah you were right mon2 a shorted cap.And yes u were right again i finally saw the need for a thermal Camera is needed .Would of save me the headache of taking out all those caps.
But am not out of the woods yet.I powered on and it was still drawing 0.12 amps . I checked PPBUS_G3H and it is fluctuating. Greenlight goes on and off still.The short hasn't come back.But it's like i never made any progress really.lol By chance any of you guys had experience with a fluctuating PPBUS_G3H ? And can maybe shed some light what to check next?

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

OMG. Sorry to hear about the troubles. What is the resistance to ground on the ppbus_g3h rail?

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

I can only offer my advice till someone more experienced on these repairs chimes in. Have repaired a number of macbooks with success with another batch incoming this week or so.

1) Remove fuse F7040 out of the circuit (just desolder it for now). Is the PPBUS_G3H line @ U7000 stable now or still fluctuates?

2) With F7040 out of the circuit, how is the green light on the charger?

3) With F7040 out of the circuit, what is the voltage at the ANODE (back of the diode) of D6990? Value @ CATHODE of the same D6990?

4) Value of PPVIN_G3H_P3V42G3H which should follow the DCIN from the power adapter. Is it close? Does this fluctuate?

5) Once the PPVIN_G3H_P3V42G3H enters U6990, the 3v42 volt rail is generated and this powers the one-wire circuit inside the hood of the power adapter. Is the 3v42 rail stable @ pin 2 of inductor L6995?

If any value is out of line, remove the power source and check the resistance to ground of that leg of the circuit. If the leg is very low in resistance, then most likely you have another shorted cap.

Again, some comments on what we have seen during our repairs. Tomorrow I think others will chime in to assist.

The premise here is, I think that excessive current is being drawn on the 3v42 rail and the switching regulator is cycling to OFF/ON mode and causing your external green light to cycle as well.

I am assuming that your external adapter is ok and ideally is the original factory version.

[MobileXT]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

I just wanted to report back on some news on this macbook pro.I got frustrated and decided to just take out all 22 caps on that rail. Really wasn't in the mood to take out one by one and check for when the short was gone.So took out 18 of them and the short was still there.The last 4 took them out and short was gone.So it's either C1755 or C1752 . One of them was looking burnt underneath the Cap itself. So replaced it and put back all caps respectively .So yeah you were right mon2 a shorted cap.And yes u were right again i finally saw the need for a thermal Camera is needed .Would of save me the headache of taking out all those caps.
But am not out of the woods yet.I powered on and it was still drawing 0.12 amps . I checked PPBUS_G3H and it is fluctuating. Greenlight goes on and off still.The short hasn't come back.But it's like i never made any progress really.lol By chance any of you guys had experience with a fluctuating PPBUS_G3H ? And can maybe shed some light what to check next?

Look Like ISL6259

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Okay this mobo is playing some type of weird game with me. @MobileXT you were right.It seems to be the ISL. I ended up reflowing it again.And i got fan spin and amps drawing.But here is the catch.When the board cools down am back to square 1. No fan spin 0.13amps. I had already before slapped in a new ISL chip after i cleaned the board thoroughly The same day i got the board for repair. And well i got that fan spin and boot up twice as soon as i replaced the ISL. But after a while it stopped booting and no fan spin and 0.13 amps.So wondered if the old ISL may have been good.So didn't think much of it.Cause ended up discovering that short on PP1V5 which you guys helped me sort out yesterday. But just now when i reflowed the ISL again. I got it to boot up 3 times with fan spin.But when the board cooled down no more fan spin and 0.13 amps.I took my time this morning and properly cleaned the pads and put fresh leaded solder and re-solder the ISL back in.I really don't want to waste another new ISL only got 4 left. Do you guys think I should replace the ISL with a new one or the problem can be something else in an around that area.When i first posted I tested all the resistors around the ISL and all of them were showing correct values. Really don't want to put a new ISL and then the problem persists. But let me know what you guys think.

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Remove the fuse and then check if any more caps are shorted on that line. What is the resistance of the leg after the fuse?

Is 3v42 stable?

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Okay i removed the Fuse and measured it's pads
Pin 1 starts with 1.925M and keeps climbing upwards
Pin 2 0.430M and after 8 seconds then drops too 44.4K
Yes PP3V42_G3H is stable

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Is the green light of your charger still cycling on / off?

Is the adapter an original and turns on the led after a second or so after mating ? If the green light is immediately on then it is not the real apple version.

The adapter is known good and is able to power this model?

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Is the green light of your charger still cycling on / off?

Is the adapter an original and turns on the led after a second or so after mating ? If the green light is immediately on then it is not the real apple version.

The adapter is known good and is able to power this model?

Thanks for that Tip.ButThe green light comes on after like 5 seconds when i plug it in.This tip i have been using it with my bench PSU for all macbook pro 2012 820-3115 boards. We have a lot of that model in our country.The customer dropped 2x identical Macbook pro 2012 on Friday.One with a USB issue and this water damaged one am working on right now.I used this same tip to repair the one with the USB issue no problems.Also all macbook pro 2012 820-3115 i have done in the past and fixed i used this same tip.My friend borrowed my original charger.Will get it back by this evening.

On a good note Mon2 You sent me on a good trail. Took your advice and was checking all the caps and stuff on the PPBUS_G3H line Pin 2 ..And while going tru right next to one of the caps on that line i stumbled upon some bad corrosion on U7770 especially pin 3 P1V5S0_EN as seen in the pictures below
I cleaned it up and replaced the cap to the top of it and also U7770 and now the machine boots stable and now draws 0.80 .No more problems with no fan spin and 0.13 amps even if the board is cold.Only issue I have now seems to be i can't get any picture.So will continue troubleshooting till i can get some picture.But it seems to be functioning so far.Will report back once i get picture.Thanks a lot my friends.

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Very nice. Some progress.

Place the parts back on to allow for a proper boot to the desktop.

During the booting of the machine, shine a flashlight onto the back of the Apple logo - do you see the logo and/or desktop icons?

If yes, your backlight IC (LP8550?) is not working or being pulled down due to more corrosion. Check for the 25-35 volts from this LP8550 (have not checked if this part is onboard but is popular with macbook designs).

Please confirm the value of this rail - you should be able to probe this pin from the LVDS blade connector that connects the screen.

If you do not see any graphics (with the flashlight) then you may have corrosion of the LVDS cable / contacts - please inspect.

Kinda cool on this debugging...

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

okay yes my friend.Backlight fuse is good .No logo when i shine at the back of LCD.No numlock light on USB keyboard.But i hear it chime lol... Do you think it might be bios ? Am now about to connect an external display just for a joke.i'll report back.Real fun stuff.Okay just checked and nothing on external ofcourse.

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Perform a reset of the PRAM with the keyboard. Allow for the system to reboot twice while keeping these keys pressed down. See attached graphic.

Does this change anything?


Remove the LVDS cable and inspect for any corrosion.

Leave the LVDS cable off and check the backlight voltage levels @ U9701.

See the attached test points. What are the readings for these areas?

[platinumsteel]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Friends they really say never give up .lol Finally have success. I saw your post about the Pram reset and LVDS Cable a little late.But i had already remove the bios ...took a backup and do a Cleaned Me Region on it.I powered back on again and now it works and i have picture. Guess the bios got corrupted at some point. Thanks to everyone in here for the guidance, help and tips .It was a nice learning experience for me.Will check for stability and everything as the day progress...but all the long hours on this finally paid off.Thanks a million mon2 as well.You know your stuff.Will keep in touch on the Thermal Camera.

[mon2]

Re: Macbook Pro 820-3115-B Intermittent Greenlight Shorted PP1V5

Awesome!

Now you just need a bootable media to confirm the boot cycle.

Off topic - is the attached the best hot sauce ? My sister-in-law is from Trinidad and is recommending that it is worth the hunt. Curious on your comments.