HP G62 Quanta AX3 No power

[p1muserfan]

Have power until PQ47 (p. 25), 19v at drain but nothing else. N-channel fet needs high voltage to gate, correct? What components determine the voltage to the gate? Looks like PQ51 (have 4.8v at pin 2), PR155 (0 on both sides), and PR158 (29v on one side, 0 on other side). Would like an explanation if someone can. Thanks

[khaahk]

Re: HP G62 Quanta AX3 No power

Reprogram bios first, it is typical fault with them.

[p1muserfan]

Re: HP G62 Quanta AX3 No power

Reprogram bios first, it is typical fault with them.

Bad bios will prevent needed power to board?

[khaahk]

Re: HP G62 Quanta AX3 No power

Yeah - maybe not in your case. ACOK# should be low to pull PQ47 gate up to 28V.
Check DCIN, ACSET and EN pin voltages on ISL6251.


Do you have a correctly working HP adapter (center pin AD_ID) should be about 7V when connected to mainboard?

[p1muserfan]

Re: HP G62 Quanta AX3 No power

Yeah - maybe not in your case. ACOK# should be low to pull PQ47 gate up to 28V.
Check DCIN, ACSET and EN pin voltages on ISL6251.


Do you have a correctly working HP adapter (center pin AD_ID) should be about 7V when connected to mainboard?

Have voltage on following pins of PU6
1-VDD-5v
2-ACSET-2.1
3-EN-1.1
8-VREF-2.38
23-ACPRN-0
24-DCIN-19

Also have .9v on pin 3 (AD_ID) of DC_IN connector
What should my gate voltage at PQ47 be?

[khaahk]

Re: HP G62 Quanta AX3 No power

PQ47 gate should be about 28v when PQ51 gate is low.
Check PU4 pin8 output.

[p1muserfan]

Re: HP G62 Quanta AX3 No power

PQ47 gate should be about 28v when PQ51 gate is low.
Check PU4 pin8 output.

PR158 is my problem then because I have 28v on one side but nothing on the other. It does measure 150k like it should so why no voltage on the other side?

[meritosari]

Re: HP G62 Quanta AX3 No power

just want share my notes

[khaahk]

Re: HP G62 Quanta AX3 No power

if PQ51 gate is low (are you measuring correct pin?) and you have 28V on PR151 one side and the other is near 0 then measure resistance from PQ47 gate to GND and post result.

[p1muserfan]

Re: HP G62 Quanta AX3 No power

if PQ51 gate is low (are you measuring correct pin?) and you have 28V on PR151 one side and the other is near 0 then measure resistance from PQ47 gate to GND and post result.

I have no voltage on any pin of PQ51, only pin 1 is short to ground and it tests good in diode mode source/drain. Gate of PQ47 not short to ground. Nothing on either side of PR155 also.

[p1muserfan]

Re: HP G62 Quanta AX3 No power

Can I put voltage to gate of PQ47 with my power supply? 28 volts?

[khaahk]

Re: HP G62 Quanta AX3 No power

i would remove pr155 and see what happens.
pq50 and pq47 gates are connected, so check pq50 also.
I don't like ad_id so low voltage.
Is any current drawn from adapter?
3.3V and 5V rail resistance not very low?
Does the machine work from battery?

[p1muserfan]

Re: HP G62 Quanta AX3 No power

i would remove pr155 and see what happens.
pq50 and pq47 gates are connected, so check pq50 also.
I don't like ad_id so low voltage.
Is any current drawn from adapter?
3.3V and 5V rail resistance not very low?
Does the machine work from battery?

PQ50 gate voltage the same as PQ47, about .2v
3.3 and 5V coils measure high resistance (that's good)
Battery is dead, can't test
Not sure I want to remove PR155 and check without it
What determines the gate voltage for PQ47?
How does PQ51 and voltage across PR160, 155, and 158 work?
Need to learn circuit theory

[khaahk]

Re: HP G62 Quanta AX3 No power

PR155 and PR160 and switch (PQ51) make up resistor divider which determines where the high voltage will be, depending on the switches state. Same for PR158 and PR155 and PQ7.
PQ 47 gate is driven by two signals:
#ACOK (that is at correct level coming from isl6251)
ACOK_IN (driven by #D/C signal through PQ7 coming from EC)
by removing PR155 you eliminate the other signal from control and you should have PQ47 open. What happens then will remain to be seen.
Strange is that the #D/C signal comes from EC, which should not be powered on yet and you have 0.9v on AD_ID, it should be higher.
So it could be a bad power brick, dead ec and so on.
You have not provided the current consumption, how much is it?
Also do you have any voltage on 3.3 rail - PL8?

[p1muserfan]

Re: HP G62 Quanta AX3 No power

PR155 and PR160 and switch (PQ51) make up resistor divider which determines where the high voltage will be, depending on the switches state. Same for PR158 and PR155 and PQ7.
PQ 47 gate is driven by two signals:
#ACOK (that is at correct level coming from isl6251)
ACOK_IN (driven by #D/C signal through PQ7 coming from EC)
by removing PR155 you eliminate the other signal from control and you should have PQ47 open. What happens then will remain to be seen.
Strange is that the #D/C signal comes from EC, which should not be powered on yet and you have 0.9v on AD_ID, it should be higher.
So it could be a bad power brick, dead ec and so on.
You have not provided the current consumption, how much is it?
Also do you have any voltage on 3.3 rail - PL8?

Thanks for your explanation on the gate circuitry.
The power brick I use is universal with different plug ends for different boards. It also has digital readout for volts so if I have a short on a board the adapter cuts off.
If the EC is dead I have no way of knowing, I need a frequency counter to measure the crystal for it, then maybe it would generate the D/C# signal?
I'm sorry, how do I measure current consumption from adapter?
No voltage on PL8, I need voltage to PU5 first, no?

[khaahk]

Re: HP G62 Quanta AX3 No power

Have you tried the adapter on another HP machine? Or try a 100% working HP adapter first.
Maybe you are trying to fix a working mainboard.

[Th3_uN1Qu3]

Re: HP G62 Quanta AX3 No power

Flash BIOS, then do anything else. If you have no light on the adapter jack but no short anywhere, it's usually BIOS on these. And yes make sure you use a genuine HP adapter. Some of them have an adapter detection circuit. Not all of them, but some do.

[p1muserfan]

Re: HP G62 Quanta AX3 No power

Flash BIOS, then do anything else. If you have no light on the adapter jack but no short anywhere, it's usually BIOS on these. And yes make sure you use a genuine HP adapter. Some of them have an adapter detection circuit. Not all of them, but some do.

Flashed bios, no help, even with correct HP adapter.
I've got an almost identical board (DAAX3MB16A1) that receives power so I've got a "blueprint". There has to be 26v ACOK_IN from PQ7 and then across PR155. What does the # after D/C which is the base of PQ7 and comes from the EC mean? Is that something that can be measured? Is it a signal that can can be seen with a scope?

[Th3_uN1Qu3]

Re: HP G62 Quanta AX3 No power

I'll check the schematic and try to help when i have some time later, i know i fixed a few of these with this kind of problem. One was a leaky MOSFET, other a blown resistor, and the third one an open diode.

[khaahk]

Re: HP G62 Quanta AX3 No power

The source of the 26V on PQ7 is the +VH28, the voltage comes through PR158 and PR155 and then ACOK_IN either gets low or high value depending on #D/C signal status which is applied to PQ7 base.
The marking # means that it is an active low signal - for example if we are talking about ISL6251A pin 23 - the ACOK# means that the AC is ok if the signal is logical low.
The opposite would be ACOK meaning that AC is ok if the signal is logical high. What does the D/C means - not exactly sure, it is an output from EC.
If you have tried another adapter and the AD_ID was still 0.9V then look at it closer - D16, R62, R61. Take comparsion from the working board.
Measure current drawn from the + and AD_ID pins - use your multimeter current measuring (you can cut the wires from the dcjack if it is connected with cables to mainboard).