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[SOLVED]820-00923 Doesn't turn on with battery plugged in.

bjf

bjf

Member
*Title should be 820-00239*

This otherwise functional 820-00239 board won't turn on when the battery is plugged (with or without the power adapter plugged in). Known-good battery. Voltage is going to the board normally, same as a known-good logic board. PPBUS on both boards is at 11.4V with just battery plugged in.

Board was liquid-damaged. I attached pre-ultrasonic pictures.

I've seen this before but I'm not sure what's happening. Something on the board is telling it not to turn on.

The 6 pins on the connector are measuring the exact same in diode mode as a known-good board.

Any ideas?
 
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bjf

bjf

Member
No Title

Pre-ultrasonic pictures.
 

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bjf

bjf

Member
It works normally with the power button with the adapter plugged in. You can shut it down, turn it on with the power button, everything normal, but as soon as I plug in that battery cable, it won't turn on. I checked and cleaned up everything around U7000. All pads are good and measurements all match a good board.
 
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dukefawks

Administrator
Only thing I can see that may cause an issue would be BMON_IOUT. R5679 got corroded? Got another board to compare voltages?
 
bjf

bjf

Member
R5679 is not on the Touch Bar boards. The whole U5710 area is basically No Stuff. BMON_IOUT has nothing actually in the circuit. R5679, U5710 and R5675 were all left off of this board. Any other thoughts? There seems to be some sort of signal telling the board to stay off once I plug in the battery, some type of sensor or safety feature.
 
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dukefawks

Administrator
I'm not sure. Could be the system measures current draw with R7060. Was there any liquid there? Checked the resistors and traces there?
 
bjf

bjf

Member
There was some corrosion at R7061 and R7062. I replaced them along with C7020. No change. Traces and pads are all good. Continuity is good on all the lines. R7060 seems fine. It's hard to measure it because it's so low, but it's not blown open. Do you every have any luck replacing that main sense resistor on other boards? I'm not sure if I've ever fixed a board replacing that main resistor.
 
bjf

bjf

Member
It looks like U7000 might be damaged. I measured the 40 points underneath it and all are good except 27 - PM_EN_P3V3_G3H. It should be .589 in diode mode and it's at .088. I pulled U6903. No change. The balls around the edge of U7000 are very visible and look clean. I've run a whole lot of flux underneath it. No change. I haven't replaced an ISL9239 yet. I have a donor board I can pull one from, not sure it's going back on though. I ordered some from Louis, so I'll use those if I can't reball this one.
 
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dukefawks

Administrator
I'm worried that they may have firmware just like the ISL95530 on the A1534 boards. You can try Louis's chip first to confirm this. If it does not work then be very careful and save the donor chip as it will be your only chance to fix this.
 
bjf

bjf

Member
Ok thanks, I got it going. I used a U7000 from a donor 820-00840. I've never done a BGA chip that big without reballing it first. It was a little tricky but it's working fine with all 40 points measuring correctly. Works on battery and adapter. Charging normally. Thanks for your help.
 
bjf

bjf

Member
Yes, and it would have been a lot easier with solder balls on the chip. I'm sure we'll find out soon enough though if the new chips work. I'll update you once I try using one of them.
 
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