820-00165 Green Light, No Fan Spin, CPU Gets Warm!

[computercaverva]

Got this unit in, no signs of liquid damage, however one of the WIFI antennas was allowed to get in between the bottom case panel and the JTAG connector and visibly crushed the connector. I have removed the villainous JTAG and have noticed that over time to the CPU gets warm and almost to operating temperature under the heat sink. I have all S5 rails and I have 8.58V PPBUS. CPU VCORE is 0v and diode mode reading is 0.007 known good is 0.012. No S0 rails or S3 rails. Is this RIP for the CPU?

 

[dukefawks]

Only way the CPU can get hot without the machine powering on is a shorted FET allowing PPBUS to get to the CPU. Measure voltage on CPU Vcore and see how high it is.

 

[computercaverva]

I get 0V on PPVCC_S0_CPU as well as the PH1 and PH2 variants of the rail. I do have the 8.58V on ISNS Computing rail going to the FETs 7310 and 7320 I do not have any of the data lines going to the FETs to prompt them to open. I thought this was because the controllers were not being told to open the FETs and when I checked the controllers U7310 and U7320 I noticed there since PP5V_S0 is not present those controllers aren't being powered. There is no short on PP5v_S0, I guess it is possible that the controllers may not be straight to ground but still dissipating most of the voltage needed to power the CPU?

 

[dukefawks]

Remove the heatsink from the CPU and feel if it is really getting hot. If it is then find the rail that has power on it. The CPU will probably already be dead though.