UX32VD 2.1 No Power *Have BoardView*

[ngen33r]

Trying to find out what is keeping this board from powering on. So far I have checked a few things. I believe at least one problem is with the +3VSUS. This goes to a lot of components and is a total pain to check with a short.

PU8100 / RT8239B is getting hot but I am not sure if that is the cause. I am hesitant to remove it before checking other things. I might just need to and see what happens. I think I will start by injecting 3V to the +3VO and see if I can locate a hot spot as I slowly ramp the current up.

+3VO - SHORT TO GND
+3VSUS - SHORT TO GND
+3VO = +3VSUS PJP8102 POSSIBLY CONNECTED?

P_3VSUS_LX_30 - SHORT TO GND (PQ8101 REMOVED)

P_3VSUS_LX_30 -> +3VO (VIA INDUCTOR PL8100)

P_3VSUS_SNB_S -> GND (VIA RESISTOR PR8130 1 OHM)

P_3VSUS_VSENS_10 - SHORT TO GND (PC8112)

P_3VSUS_VSENS_10 = +3V0 PJ8100 POSSIBLY CONNECTED?

+3VSUS -> +V3.3_VCCSPI

TO DO
CHECK +3VSUS -> GND
C2802
C2705
C4550

[BlueMidnight]

Re: UX32VD 2.1 No Power *Have BoardView*

The 3V/5V regulator getting hot is indeed usually a result of a short on one of the 3V or 5V rails.

Yes, +3VO and +3VSUS are just different names for the same rail on each side of PJP8102.

Since you have a bench power supply, you will hopefully be able to find the shorted component with that. However, it's also possible to make good use of those solder jumpers like PJP8102. You can desolder them and then measure which side the short is on.

Likewise, you can find choke points (single components that the power rail passes through) and remove them (or just slide/rotate them until they no longer make contact on both sides). These often take the form of resistors, inductors, or FETs. After removal, measure which side the short is on.

[Mazorca]

Re: UX32VD 2.1 No Power *Have BoardView*

The 3V/5V regulator getting hot is indeed usually a result of a short on one of the 3V or 5V rails.

Yes, +3VO and +3VSUS are just different names for the same rail on each side of PJP8102.

Since you have a bench power supply, you will hopefully be able to find the shorted component with that. However, it's also possible to make good use of those solder jumpers like PJP8102. You can desolder them and then measure which side the short is on.

Likewise, you can find choke points (single components that the power rail passes through) and remove them (or just slide/rotate them until they no longer make contact on both sides). These often take the form of resistors, inductors, or FETs. After removal, measure which side the short is on.

That is the best advice I have had in a while. I have two motherboards with step-down converters that heat up, and I thought that I would just need to replace them, and presto, all fixed...not so! Excellent advice from BlueMidnight, in a way, this is a learning experience, and tells us that there is no easy solution, just ways of approaching repairs.
Thank you so much.

[ngen33r]

Re: UX32VD 2.1 No Power *Have BoardView*

I am going to use this space to document what I have and have not checked. I am currently using 3V current limited to 200mA and using alcohol evap to identify the bad part. I may need to bump up the current but for now I will start low.

Well after testing I found that U2001 is the problem. I do not have BGA equipment so I think this duck is dead.

Part alone is $56
https://www.mouser.com/ProductDetail...dnzX%2Fw%3D%3D

Unless someone knows a reputable person that can do the repair, I will look for a new board.