820-00923 no power

[Kyle93]

Arrived with liquid damage mainly in U3100 area. Before working on the board it did get 20V and appeared to be booting. After replacing surrounding affected components board got stuck at 5v. All LDO voltages present. Replaced U3100 to rule out but no change.
PP3V3_G3H fluctuates around .500v-.900v C3200 however it appears everywhere else on the board 3.3V

What could be causing 3.3v to flucuate only on c3200? No short to ground and already replaced C3200

 

[2informaticos]

Broken trace; run a wire to other convenient 3V3_G3H point.

 

[Kyle93]

When the wire is ran the usb amp meter turns on and off every few seconds

 

[2informaticos]

More damage in that area; maybe some trace/pad under CD3215.

 

[Kyle93]

ran wire to different spot and meter is not boot looping anymore. solid 3.4V on C3200 now but still only 5V.

Any specific pads that should be checked under CD3215?

 

[2informaticos]

The one for 3V3_G3H first.
Be aware, the opposite side could be affected by the heat.
You should reball/change U3100 and check its surrounding components and traces.

 

[Kyle93]

3V3_G3H continuity is good to both CD3215s

Replaced U3200 as well to rule out. Checked all surrounding components and traces thoroughly, everything looks good.Both CD3215S LDO rails measure good.

Noticed UPC_XB_GATE1 is only 11V AND UPC_GATE2 only 6.5V

What should ve checked next?

 

[2informaticos]

Don't waste time measuring gate pin of any MOSFET.

Something happened when you work on the board, if was switching to 20V before.
Heat affected some corroded area, or BGA chip.
Inspect U2890 solders and traces.

Do you get now 1V1 LDO on the powered port?

 

[Kyle93]

U2890 solders and traces look fine, they were not affected by the spill.

1V1 LDO missing on U3100 and U3200 even though both CD3215s were replaced.

 

[Kyle93]

Replaced both CD3215S once again to rule out the chip being bad or fake by using reballed untouched ones from donar.

Still 0v on 1V1 LDO U3100 and U3200

1v1LDO is however present on UB400 and UB300.

Found other post about this issue to check voltage on R7020. 5V is present.

What else could be causing this?

 

[2informaticos]

1V1 LDO appears on the other ports?

 

[Kyle93]

Replaced both CD3215S once again to rule out the chip being bad or fake by using reballed untouched ones from donar.

Still 0v on 1V1 LDO U3100 and U3200

1v1LDO is however present on UB400 and UB300.

Found other post about this issue to check voltage on R7020. 5V is present.

What else could be causing this?

 

[2informaticos]

Something happened when you've worked on that area.
Possibly internal trace damaged; liquid spill could got between copper layers.

 

[Kyle93]

anything else worth trying or checking or does it sound unrepairable at this point??

 

[2informaticos]

Not too much ,
Some traces can't be checked, as no test points available (BGA --> BGA).