[S|OLVED]820-4924-A sees but does not charge battery

[Cocobill]

Hello,


I got this logic board 820-4924-A. Minor water damage here and there, nothing crucial as it was working but not recognizing SSD. I ultrasoniced the board and the SSD and it works! Only issue, the battery is recognized but not charging. The battery itself is quite new, 11 load cycles so should not be the problem. History of the board is: was bought new 12 months ago, had a coffee spill after some weeks and has been in a drawer ever since.


Measured ISL resistance 17/18 26.80Ohm and 27/27 20.4Ohm.


Data lines on battery connector, diode mode


smbus_chgr_scl=0.500V

smbus_chgr_sda=0.500V


What do I measure next?

 

[JohnB8812]

Resistance between 17 and 18 is high so there’s your problem. Most likely one or both resistors are blown for battery current sensing. Also make sure traces to ISL are good

 

[Cocobill]

Thank you JohnB8812, you were right.

R7150 pin 2 was blown so I replaced the resistor and run a wire from pin 2 to a probe point near R7150. Nothing changed... So I decided to replace the ISL. Replacement ISL orientation and joints OK, as I put the board in the case and connected the battery, I heard a zap, there was a shortcut of some sort, even a hint of a smell of something burnt.

So now I'm back at square one, having no light in the charger... Will get back to you as soon as I get it back.

 

[Cocobill]

OK the wire I run from R7151 (not R7150...) shorted with nearby C7100 and that's what destroyed green light. Now I put a new ISL, run a new wire but now I get a green light flashing on and off every 1.5 second
if battery is connected, and steady green light if battery not connected. What could be the problem?

 

[JohnB8812]

Check your resistance between pins 17 and 18 again it needs to be around 3.9 ohms. If not, therer is still something going on there. If so, what is the voltage on 3V42 and PPBUS with the battery plugged in?

 

[Cocobill]

Resistance 17/18 is 22 something MegaOhms! Checked R7151 and R7152, both read OK. The wire I run from pin 2 of R7151 to a probe point near R7150 is clean. Tried new ISLs and a used one from a doner board. Same ridiculous high reading on 17/18. What am I doing wrong?

 

[JohnB8812]

You need to check the traces from the ISL to those resistors and check the traces from this resistors back to the shunt resistor there is a break in the line somewhere.

 

[Cocobill]

Shunt resistor was out of specs and I used one from a late 13 retina. Now resistance 17/18 is 2.7Ohm but I still get a flashing green light...

 

[JohnB8812]

Voltage on PPBUS with and without the battery? Voltage on 3v42 when the light is flashing?

 

[Cocobill]

PPBUS with charger only 17.72V, with both fluctuating between 16.35 and 12.12V. 3v42 is reading 3.39V and steady while flashing green light. Is it OK to keep the shunt resistor from late 2013 Retina, although slightly different resistance?

 

[JohnB8812]

Yes shunt is ok, but 17.72 is wayyyy too high! That sounds like Q7130 is shorted. Replace the ISL, Q7130 and Q7155 all at the same time and see what happens.

 

[Cocobill]

Getting there!... I replaced ISL Q7130 and Q7155, put it together, connected battery and now I'm getting a steady green light turning into orange within seconds! But, Mac does not power on. PPBUS is 12.96V. Without battery, PPBUS is 12.50V, I'm getting a chime but no image.

 

[JohnB8812]

12.96 with the battery? That's a little high possibly the battery causing it tho. When you say no image can you see anything if you put a flashlight to the Apple?

 

[Cocobill]

Right, I meant no backlight. I made a stupid mistake! While putting the board back in the case, I did not see the camera cable and it got underneath it so something is shorted

 

[JohnB8812]

Ok does it turn on still with no backlight? If so, what voltage do you get on PPVOUT_S0_LCDBKLT with the screen connected of course?

 

[Cocobill]

Good news first: battery is charging! OK PPVOUT_S0_LCDBKLT is 15.86V, should be 55V, shouldn't it?

 

[JohnB8812]

Ok so for one good! Backlight on these I think should be around 30ish volts. 15.86 volts would suggest that the circuit isn't boosting properly. Check for backlight enable and PWM and go from there. I'm not as familiar with backlight circuit on Retinas, but I'm sure Duke and others on here are.

 

[JohnB8812]

Def try a PRAM reset first and make sure the screen is known good 2015 13" LCD.

 

[Cocobill]

I use an 820-3462.pdf and .brd for this board, which is sub optimal. Are these 2015 retina files available for buying?

 

[Cocobill]

Thank you for the offer, John! I just found and downloaded the files, was surprised how easy it was this time, got lucky I guess. Back to work, how do you measure backlight enable if it is underneath, as you have to connect the screen. Unless I am supposed to have a loose screen and battery to make this measurement...