HP G72 no DC jack led and no start

[pecrie]

Hello ,

I have been working on this MB - for some time now.Like I said , the led in the DC jack is not lit.

There is no 3.3V on the Bios Rom (so the MB will not start).I do have the 3.3V on the EC SPI Bios chip.

I have also noticed that on some (double) mosfets there is 19.xxVolt.
But I am missing 1.x V -5.xV - 1.1V - 3.3V (bios) - 0.9V (for CPU)

According to the schematic +V3.3A / +V5A should come from the EC IT8502E.But I'm not sure on what pins they should be.

So any ideas ??

I attach the schematic to this post

[diif]

Re: HP G72 no DC jack led and no start

It's PU850 that creates the 3v and 5v not the IT8502E page 35.

[Techtiger]

Re: HP G72 no DC jack led and no start

Yep that’s correct PU850 check on the coil PL11 & PL801 for Voltage 3/5V, check pin 6 of PU850 voltage

[pecrie]

Re: HP G72 no DC jack led and no start

Yes , but I cannot measure it on the MB.All the inductors (transformers) have 0 Volts.
PU850 can create 3v and 5v but where are they going ?
No voltage on the CPU -

[pecrie]

Re: HP G72 no DC jack led and no start

On coil PL11 there is 3.3v.On coil PL801 is 0 Volt.
Pin 6 of PU850 has 19.x Volt
Pin 7 has 4.99 Volt

So is the voltage on Pin 6 of PU850 too high ??

[Techtiger]

Re: HP G72 no DC jack led and no start

Check Pin 72 of SIO IT8502E for SMART_ID If your motherboard will not recognize the charger the DC check light will not light up

[ktmmotocross]

Re: HP G72 no DC jack led and no start

On coil PL11 there is 3.3v.On coil PL801 is 0 Volt.
Pin 6 of PU850 has 19.x Volt
Pin 7 has 4.99 Volt

So is the voltage on Pin 6 of PU850 too high ??

If u dont know basic pins functions, than check IC datasheet.
VIN is main power input and 19V is ok

[Techtiger]

Re: HP G72 no DC jack led and no start

On coil PL11 there is 3.3v.On coil PL801 is 0 Volt.
Pin 6 of PU850 has 19.x Volt
Pin 7 has 4.99 Volt

So is the voltage on Pin 6 of PU850 too high ??

Pin 6 is power supply for that IC 19V ,for the PL801 put your multimeter in Diode mood and test for Ohms both sides of the Coil ( if you don’t know how to test Ohms check out YouTube)

Near the PL11 coil there is a JUMPER PJ542 test that point for 3.3V

[pecrie]

Re: HP G72 no DC jack led and no start

@techtiger
Pin 72 of IT8502 has 0 Volt.And yes , I tested the PL801 in diode mode with respect to ground.
On both sides it beeps.

I will check the Jumper PJ542

@ktmmotocross ,

The schematic also shows for VIN - pin 6 - of PU850 3.3V.
Or I am interpreting this in a faulty way

Ok , I did check PJ542 there is 3.3V (I did mention this in one of my earlier posts)
I don't have 5.xV on coil PL801 and also not on the Jumper next to it.
So , no 5.xV then some leds will not lite up.

I did test the coils PL11 and PL 801 in diode mode - there is no short circuit to ground.

Something is preventing the 3.3V to go to the Bios Rom and the 5.x V is also not getting through.

I'm not sure if I will keep on working on this MB - it has taken me too long already.
But we will see

[ktmmotocross]

Re: HP G72 no DC jack led and no start

@techtiger
Pin 72 of IT8502 has 0 Volt.And yes , I tested the PL801 in diode mode with respect to ground.
On both sides it beeps.

I will check the Jumper PJ542

@ktmmotocross ,

The schematic also shows for VIN - pin 6 - of PU850 3.3V.
Or I am interpreting this in a faulty way

Ok , I did check PJ542 there is 3.3V (I did mention this in one of my earlier posts)
I don't have 5.xV on coil PL801 and also not on the Jumper next to it.
So , no 5.xV then some leds will not lite up.

I did test the coils PL11 and PL 801 in diode mode - there is no short circuit to ground.

Something is preventing the 3.3V to go to the Bios Rom and the 5.x V is also not getting through.

I'm not sure if I will keep on working on this MB - it has taken me too long already.
But we will see

3.3V IN means it is input voltage for 3.3V highside mosfet. if u r not sure see IC datasheet, there are very usefull info, with description of every pin of IC.

beeping means nothing u must see value of that resistance to ground

did u check that charger id pin?


this board is not hard, but u must know what to look for. it is a good board to learn, because it is easy

[piernov]

Re: HP G72 no DC jack led and no start

As always on HP the AC adapter has to be recognized before anything. If you don't have the DC in LED lighting up, it will not turn on.