HP PROBBOK 450 G4 +3VPCU SHORT

[NConstantinou]

HI ALL.
I HAVE M/B DA0X83MB8H0 REV:H WHICH HAS SHORT THE +3VPCU RAIL.
WHICH POINT CAN I INJECT VOLTAGE IN ORDER TO FIND WHERE IS SHORT AND AT WHAT AMPS!

I GOT A LOT OF CAPS SHOWNING SHORT.

THANKS

[FriedFred]

You can try with a voltage of 0.5 Volt. Not higher if you work nearby the CPU or GPU. Try for the first attempt 1 Ampere.
This little voltage you can inject nearly everywhere, because it will not switch-on semiconductors.
But be careful. Semiconductors start conducting up from 0.6 Volt.

[mcplslg123]

Remove the +3VPCU coil and inject 1V/5A on the shorted side. Wait for some time to feel anything hot.(first make sure you dont have short on +19V rail)

[NConstantinou]

By removing the +3VPCU and connect power supply to short side in only apply 1v 0.65A.
if i apply higher A the short on power supply disappears.
i can only apply 1v 0.65 Ampere. if i apply more amps the short dissapears.
with this setup nothing gets worm.

[FriedFred]

I suggest to disconnect the DC-DC converter and check the DC-DC converter and the rest of the +3VPSU rail.
For this, you just open the PJP7 connection and then you can test the DC-DC converter by itself.

[NConstantinou]

Unfortunately there are no PJP junctions on board as described on schematics that is why is more difficult to find out the problem.

[FriedFred]

In the black colored screen-shot above, there is a red marked item. This is the "PJP7" junction, you need to open.