820-3437 No boot

[wirelessplanet]

Checked under microscope no liquid damage. get orange light. fan spins for a half second a every couple of seconds.

PPBUS - 8.59v
PPVCC_S0_CPU - pulses at 1.6v when fan spins(i'm assuming this is vcore?)
ALL_SYS_PWGD - Puleses at 3.3V
Pin 8 on u1950 - 3.34 but drops every second.

 

[dukefawks]

Pin 8 of U1950 goes directly to 3V42 as you can see. This would mean 3V42 rail must be pulsing too.

 

[wirelessplanet]

any suggestions on where i should start to fix 3v42? never had a pulsing rail before.

 

[dukefawks]

Is 3V42 really pulsing the the first question or is it a dodgy measuring on U1950.

 

[wirelessplanet]

double checked it ....sorry looks like i messed up on the measuring.

 

[dukefawks]

So the usual power cycling. Check the usual suspect, J6100, U6100 and termination resistors, U1950, U1900 and traces. Known good BIOS?

 

[wirelessplanet]

ill check the rest. how can i tell if bios is good? The board has never been touched. and no water damage.

 

[dukefawks]

Swap BIOS chip with a known good one. Of course only for testing as the original BIOS will then need fixing.

 

[wirelessplanet]

okay just received a few dead boards from china. I know its stupid question but just to make sure bios is u6100 right

 

[dukefawks]

U6100 is the ROM indeed. Make sure the ROM actually is good, donor boards may have the ROM erased or corrupted.