HP EliteBook 840 G2 5v pwm regulator issue.

[Francisco.s]

Can someone identify 5v pwm regulator, (VRP5V0A) from attached photo?

The motherboard is an Inventec CHICLET 6050A2637901-MB-A02 (UMA)

It has some minor?? changes/differences seeing the schematic.

The schematic says that 5 volts regulator is the well known TPS51225, but on the motherboard 5 and 3 volts regulators are two independent chips. ( not a TPS51225 dual pwm regulator)

Problem with this mobo is that 5 volts are present only for 3 seconds an then goes to zero.

3.3 volts are present all the time.

Please help, I can't find any datasheet for chip U6150.

Thanks in advance.

[khaahk]

Re: HP EliteBook 840 G2 5v pwm regulator issue.

Most times it is useful to put the top marking of the chip to aliexpress search box.
It should be NB676A:
https://www.monolithicpower.com/en/d...ument_id/6389/

[Francisco.s]

Re: HP EliteBook 840 G2 5v pwm regulator issue.

Most times it is useful to put the top marking of the chip to aliexpress search box.

Hi khaahk, thanls for your help.

I did the search in ebay but not in aliexpress.

Next time I will change search engine to aliexpress, it is way more better.

[khaahk]

Re: HP EliteBook 840 G2 5v pwm regulator issue.

I have the same board on the table, it has RT7291B instead installed. So they should be direct replacement, "4m=" is the top marking. Just in case for future reference.

[Francisco.s]

Re: HP EliteBook 840 G2 5v pwm regulator issue.

The problem is solved.

EN_5V and EN_3V were always present, but VRP5V0A (5v alw) at coil L6150 only were present for 2 or 3 seconds due to a bad capacitor in this rail.

A bit difficult to find this capacitor, there are no names for capacitor and resistors, and schematic is also wrong.

I have to use the schematic of two inventec models to follow the circuit.

Sometimes Inventec CYCLONED or Inventec Comet matched the circuit better than Inventec Chiclet. (the last is the one it mounts)

Thanks for your help.

[reformatt]

Re: HP EliteBook 840 G2 5v pwm regulator issue.

Same board came in today which was pretty much dead. This board had reportedly died after the customer plugged in a external HDD via USB with an incorrect power supply. Heard a pop and laptop died.

The schematics here differ in this model, as the pointed out above, the 3.3V/5V supplies are discrete on the Chiclet version (correspond to U6100 and U6150). U6100 is 3B= --> RT7290A, U6150 is 4M= --> RT7291A.

The 3.3V LDO voltage was present on pin 6 of U6100, however this was not present at the MEC EC (U300). Scratched my head a while on this one as the schematic from the Comet version indicates that this connects via Pad6103. This does not exist in the Chiclet version. Checked the 5V LDO on U6150 and that was missing. The IC was indeed stuffed, and when replaced, the 3.3V for the MEC appeared. So there must be some logic in the board that only supplies the power to the EC once both 3.3V and 5V LDO's are present. I think these drive the enables for the 3.3V/5V supplies which in turn feed the EC etc.

The USB board (6050A2638201-USB-A01) was also faulty with a 12 ohm short from +5V to ground on one of the ports. With this plugged in, the fan just ran at full speed and it wouldn't switch on. There isn't much on that board, and when I pulled off U2511 (I think) that disappeared. Markiong on the IC is 2540 CC, I think it is a TPS2540 but it appears that a STCC2540 is equivalent. I had a spare board that I used though but datasheet seems to line up with whats on the board.

[ktmmotocross]

Re: HP EliteBook 840 G2 5v pwm regulator issue.

The problem is solved.

EN_5V and EN_3V were always present, but VRP5V0A (5v alw) at coil L6150 only were present for 2 or 3 seconds due to a bad capacitor in this rail.

A bit difficult to find this capacitor, there are no names for capacitor and resistors, and schematic is also wrong.

I have to use the schematic of two inventec models to follow the circuit.

Sometimes Inventec CYCLONED or Inventec Comet matched the circuit better than Inventec Chiclet. (the last is the one it mounts)

Thanks for your help.

why dont u inject? u dont need schematic for this kind of repair