820-00165 Dead

[Sykulski]

This 820-00165 came in dead by a small amount of water

Bad corrosion on U8005. Pulled and replaced U8005 with new one and wired pin1 to C8005/p1 as this trace was burned. Also replaced C8005.

Now there is no fan spin, and all pins (PP5V_S0, PCH_HSIO_PWR_EN, PP1V05_S0, PP1V05_S0, SW_PCH_HSIO) on U8005 are low (a couple of mV)

But if I pull U8005 off the board only PP1V05_S0SW_PCH_HSIO is low... The other ones PP5V_S0 = 5V, PP1V05_S0 = 1.05V, PCH_HSIO_PWR_EN = 3.3V and the fan starts spinning.

Board does not boot obviously without this chip.

Diode mode U8005:

on the board:

p1: 0.43
p2: 0.10
p3: 0.10
p5: 0.18
p7: 0.18
p8: 0.00
p9: 0.46

off the board:

p1: 0.43
p2: 0.09
p3: 0.09
p5: 0.17
p7: 0.17
p8: 0.00
p9: 0.46

What's going on ?

 

[dukefawks]

I bet when U8005 is on the board it successfully powers on but is power cycling. When u8005 is off it just hangs half way in the power up sequence.

Inspect the usual areas around U6100/traces/termination resistors, clock chip, U1950, etc.