[RIP] 820-00840 short on 3V3_S5 and PP1V8_S5G

[bjf]

This board has PPBUS at 13V. It heats up when plugged in. I found a short on 3V3_S5 and PP1V8_S5G. The CPU area and the area underneath heat up so I'm not sure if the short is the CPU itself or the circuit feeding it. PPVCCCPU_S0G is not shorted, it measures the same as a good board. Not sure if I'm looking at the usual shorted CPU or if there might be some other move here. I attached some pre-ultrasonic pictures.

 

[larossmann]

what gets hot when 3.3v is injected into 3V3_S5 ?

 

[bjf]

No Title

It looks pretty conclusively like the CPU is shorting internally, but I can't rule out a short in the circuit causing the short inside the chip. I attached some pics of the top and bottom heating up. Ignore the red outline around the CPU, that happens with reflective metal. The glow to the left in that picture on the CPU is the area that's heating up once I send voltage through 3V3_S5.

 

[larossmann]

That seems like an ope and shut case of dead CPU to me. All of my 3v3_s5 shorts besides one have been CPU on the newer boards, it was some odd logic gate or audio IC causing it before.

 

[bjf]

Yeah, that's what I figured, just wanted to get a second opinion.Thanks.