HP Probook 450 G2 - No Power

[boyop]

Hi Guys,

I'd like to start by mentioning that I'm a complete newbie at electronics and motherboard repair so please be patient with me if I sound a little confusing at times. I am however, learning fast and enjoying the ride!

I have quite a few issues with this HP probook 450 and i'll try to go through them once I get past understanding this one hurdle.

Initial problem : Orange LED was on when the charger was plugged in and Power Button LED came on when button was pressed. Both lights turned off after about 8 seconds and nothing started up.

While diagnosing the Power Supply controller in the picture shown, I may have shorted the 5VDSP at pin 1 and ENTRIP at pin 2. Since then, I no longer have an orange LED when plugging in the adapter. I now have a white LED which continuously flashes and the Power Button LED comes on without even pressing the button and stays on.

Pin1 of this controller shown in the image is now at 2v and RSMRST at the SIO is no longer present.

At the top of the page it says " Leave Entrip1 floating or drive it above 4.5v to shut down channel 1". I assume that is what I did, shut down channel 1.

My questions are:
What is channel 1?!
What does it mean to 'shut down' a channel?
Is there any way to reverse this?
How come I get 5v at the coil at PL302, (+5VDSP towards the right), yet I only have 2V at pin 1 which should be coming from the same source, if i'm right on that?

Any help would be much appreciated!


Thank you

[caspian]

Re: HP Probook 450 G2 - No Power

a channel is an internal section of the IC that generates a specific voltage such as 3.3v or 5v.
the shutdown occurs if a permanent voltage enters pin 2. Since you did a temporary short, it is not gonna be a problem.
as long as you have a stable 5v present at PL302 and a stable 3.3v present at PL303, this IC (RT8243) is working fine and do not work on it.
check other voltage rails on the board to discover which one is not present.

[boyop]

Re: HP Probook 450 G2 - No Power

Caspian, thanks a lot for clearing that up for me.

At the IC RT8207MZQW, I should be getting an output of 1.35V and 0.675V. I'm not getting any output at all at any of the output pins.

The top of the chip seems a little rough/corroded too, it doesn't have the shiny surface that other IC's have. But, could it be that this IC only outputs the 1.35V and 0.675V on the condition that SLP_S4# is present on pin 8? Or, is this irrelevant at this point?

(btw, I don't have SLP_S4, but I do have SLP_S3.)

[caspian]

Re: HP Probook 450 G2 - No Power

SLP_S3# and SLP_S4# are enabling signals to RT8207 and are important. but do not get confused with them now.
corrosion is a symptom of fault.
now you have to check all the output voltages mentioned in page 58 of the schematics.
and please confirm here all the missing ones.

[boyop]

Re: HP Probook 450 G2 - No Power

Hi Caspain,

Sorry for taking so long to reply, been a little tied up lately.

Right, I have checked all of the voltages on page 58 as you advised.

Here's what I have missing.

DDR RT8027
missing SLP_S4# input
missing 1.35V_VDDQ output
missing 0.675V VS output
missing DDR_PGD output

SY8206
missing SLP_S3# input on enable pin
missing 1.05VS output
missing 1.05V_PGD

SY8003
missing SLP_S3# input on enable pin
missing 1.5VS output
missing 1.5V PGD

TPS51622
missing 12.5V VR_ON
missing vcc_core
missing vgate

Also, here's something odd. The chips at RT880B, SY8003, which are related to VGA are not present on the board. However, when I look at photos of this board using Google, they are present on some and not on others. Could it be that someone has removed them before this board made it's way to me or is it just that this is the i3 version and it doesn't have it?

Lastly, on the opposite side of the processor, the caps seem to have blown and are shorting when I test them on board. There is some brown gluey substance around them. They definitely seem destroyed. Should I try to replace these before anything else? (I could show a photo if you require)

These caps close to the coils labelled RC176, RC179 and are on p12 of the shematic.

[caspian]

Re: HP Probook 450 G2 - No Power

if you found some board pictures without those ICs, it is OK and they should be factory settings. If someone removed them, there should be untidy solder residues left on the pads.
a photo of those caps will be helpful to decide. do not replace them now.
did you measure the page58 voltages after pressing the power button before the led turns off? they should not be all missing.

[boyop]

Re: HP Probook 450 G2 - No Power

The power LED doesn't switch off at all any more. I'm just getting a flashing adapter LED. This started since I shorted pins 1 and 2 on RT8243. I will try to take a photo of the caps and send it later today.

btw, which Voltages on page 58 should not be missing?

[caspian]

Re: HP Probook 450 G2 - No Power

Since you are getting a flashing adapter LED, the laptop is shorted and all voltage rails should be missing.
try to find the short at the 19v rail.

[electrodj]

Re: HP Probook 450 G2 - No Power

i have the same symptoms do you fix it?