I can't resolve a problem [No Power to CPU]

[hazardus]

Hi guys,

Ok, so this is my second motherboard (Dell vostro 3750) which came with no display. In both case I found the issue no power to CPU. I can't find the problem which causes the no power issue to the cpu. No short nothing.

What do you guys think?

[pholix]

Re: I can't resolve a problem [No Power to CPU]

2 new motherboards with the same fault, thats really quite rare. I know this is is stating the obvious, but on your PSU power supply unit there will be a square plug that fits directly into the motherboard, its usually within and inch or 2 of the the cpu housing - check this part of your power supply is working and connected correctly to the motherboard.

[hazardus]

Re: I can't resolve a problem [No Power to CPU]

These are not new. These are here for repair.

[hazardus]

Re: I can't resolve a problem [No Power to CPU]

I checked PU4 NPC6131:
Pin1 - nothing
Pin2 - 0.86V
Pin3 - 1.03V
Pin4 - 0.95V
Pin5 - 0.73V
Pin6 - 1.03V
Pin7 - nothing
Pin8 - nothing
Pin9 - 3.35V
Pin10 - 5.05V
Pin11 - 1.96V
Pin12 - nothing
Pin13 - 0.87V

These are on.

When off
just Pin38 and Pin39 are present.
Pin38 and Pin39 - 0.44V after press the power button both goes high to 5.1V.

[dj_ricoh]

Re: I can't resolve a problem [No Power to CPU]

resolder PU4

[hazardus]

Re: I can't resolve a problem [No Power to CPU]

I did that. I also put a new one I thought something wrong with it.
CPU has two phases and neither is working. Interesting isn't it?

[dj_ricoh]

Re: I can't resolve a problem [No Power to CPU]

so on page 41 you got all the voltages?

[hazardus]

Re: I can't resolve a problem [No Power to CPU]

Yes, I've all the voltages.

[dj_ricoh]

Re: I can't resolve a problem [No Power to CPU]

PL5,PL4,PL6 and PL9 voltage.

[dj_ricoh]

Re: I can't resolve a problem [No Power to CPU]

o lol did you test with another CPU?

[hazardus]

Re: I can't resolve a problem [No Power to CPU]

Nothing on PL5,PL6, and PL9.
PL4 is empty because CPU just uses two phases instead three.

I tried with different CPU but didn't help.

[dj_ricoh]

Re: I can't resolve a problem [No Power to CPU]

we need voltage from PU1,PU2 and PU3