820-3437 no power

[Kyle93]

Arrived with liquid coffee damage primary around U6100 area. Replaced U1900 and U1930. Board now takes a constant 430ma and CPU gets warm but PCH side burning warm with no fan spin. Checked all SPI resistors and all measure good. Continuity is good as well. Tried known good Bios with no change.

What to check next?

 

[2informaticos]

Clean J6100; remove it, if do not use medusa programmer.

Check all voltages from pages 57/58.
Also check voltage on the L/C blocks located between CPU and board edge.

Reball SMC.
Heat PCH/CPU with quality flux; try to burn eventually accumulated crap underneath.

 

[Kyle93]

PP1V8S3_EN and PM_SLP_S4_L only 0.181V

Where does PP1V8S3_EN signal come from?

 

[2informaticos]

The board consumes 340mA without PM_SLP_S4_L?
You can only have 3V3_S5/SUS and RTC voltage.
If CPU gets hot, one of these rails should have very low resistance to ground.

Post 3V42_G3H and PPBUS_G3H; discard any short on them.

 

[Kyle93]

3V42_G3H 3.42V PPBUS_G3H 8.60v

diode mode pp3v3_s5 0.024 pp3v3_sus 0.001

 

[2informaticos]

As expected, low value on 3V3_S5 and even short on 3V3_SUS.
This looks like dead CPU...

 

[Kyle93]

Bummer. Are CPUs still impossible to find for these? We do have a BGA machine.

 

[2informaticos]

CPU is not cheap and very easy you can get a refurbished/dead chip.
Change it is also dificil job...