HP Probook 450 G5 DA0X8CMB6E0 Rev. E short circuit

[martin86]

Hello, I have a problem with the board.
The mainboard switches itself on again as soon as the power is switched on. The power button LED lights up. The CPU gets warm / hot. But there is a short circuit on the board, almost every PIN is connected to ground. If a laboratory power supply is used with a few volts (2-8V), approx. 1A current is always drawn and the mainboard whistles. Since the CPU is always hot, I thought that this vl has a short circuit, how can I measure it?

[mon2]

Re: HP Probook 450 G5 DA0X8CMB6E0 Rev. E short circuit

Which PIN is showing a short to ground ? How was this tested ? Resistance mode on your meter? Which scale ? CPU rails often show this condition.

Where is the lab power supply being attached ? Is it at the DCIN of the laptop ?

See attached.

Post the voltage readings (DC voltage scale; 20V or higher is ok) for the requested locations.

Red meter lead on the test point; Black meter lead to ground (shield is OK).

Next, remove all power. Meter in resistance mode.

Check & post the resistance to ground for the +VIN rail. A very low resistance will indicate a shorted cap on the leg which is causing the power supply to shut off. It is very possible the whining you are hearing is the oscillation of the power supply turning ON (detecting the short condition) -> then turning OFF. Much like a buzzer circuit which is causing an audible buzzing / whining sound.

[piernov]

Re: HP Probook 450 G5 DA0X8CMB6E0 Rev. E short circuit

https://www.badcaps.net/forum/showpo...02&postcount=2

[martin86]

Re: HP Probook 450 G5 DA0X8CMB6E0 Rev. E short circuit

Hi Mon,

thanks for the feedback. Here the picture of the power supply being attached. I had a old DC IN Connector, i should not be a problem or?

I have on any PIN auf the BIOS Chip a Short to Ground. When i connect a USB Programmer the Programmer reboot and lost Power.

Where to i find the +Vin Test Point?

After the Mainboard where 2 Minute on Power with around 8V from the Power supply, no i looks like you write. Power on -> detecting the short condition -> Power off - > Power on -> detecting the short condition with audible buzzing.

Thanks for reply

[martin86]

Re: HP Probook 450 G5 DA0X8CMB6E0 Rev. E short circuit

Hi,

i have news, as anybody a idee. At the Beginning Power Supply Mosfet i have the 19V present. But not on every Mosfet 19V. I have Mosfet that have only 9V where i lost around the 10V?

I attached a Picture. Has anybody a idee? The Mainboard always has 1A usage, no matter to the Voltage, always 1A ?

The 4 Capacitors in the Picture, has short to Ground (0Ohm every side to ground). 0Ohm between the pads???

Thanks.