[Acer 6930G] Lower +5V problem.

[ben7]

Re: [Acer 6930G] Lower +5V problem.

I was check PQ16 before and;

FET named PQ16 for 5V_S5 out, it's using same +15V for gate. And output is stable. I mean PQ16 pin 123 is 5.07V not decreasing.

So if the problem is 15V, also this PQ16 has to be any problems too?

Well you can try to replace PQ16 but I won't guarantee that will solve the problem.

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Well you can try to replace PQ16 but I won't guarantee that will solve the problem.

No, no i guess you misunderstand, i talk about PQ16 because, this FET like PQ14. Both gates connected same 15V. But, PQ16's all voltages are ok but PQ14's not. So i meant if the problem is 15V which is you thiking about 15V cold be a problem as a 13.5V. So i just wondering if the 15V is the problem, so should both of get some voltage decraasing on them. But only PQ14 has problem...

[ben7]

Re: [Acer 6930G] Lower +5V problem.

Ok, yes indeed I got a bit confused there, sorry!

Could you check the resistance of PR94, PR95, and PR100?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

I checked 3 of them, all working fine. :\

P.S: Maybe you want to know, i replaced PQ19 too . And i checked now all MAINON_ON_G line resistors, PR94, 95, 100 , 92, 96 , 98 etc.. all working fine. PQ19 working fine.

[ben7]

Re: [Acer 6930G] Lower +5V problem.

Checked the MAINON signal?

I'm still thinking it is either a problem with the voltage tripler, or the power management IC itself.

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Yes MAINON is OK on stand by mode, 6V. When i run the computer, voltage goes 0V.

[ben7]

Re: [Acer 6930G] Lower +5V problem.

I did a little thinking, PQ30 or PQ31 could be bad. Could you test them?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Thank you so much your suggestion but, is those 2 Fets for 5VPCU side right? I mean 5VPCU is always FINE. 5.07. do you thinking still those ones could be a problem?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

I still got nothing.. any ideas? :\

[Th3_uN1Qu3]

Re: [Acer 6930G] Lower +5V problem.

The way i see it, this has got nothing to do with the switching transistors. It shouldn't, either - a transistor only runs in 2 states in a switching power supply: fully ON (low resistance) or fully OFF (open). So if the transistors have gone bad, it won't work at all. Besides, the power supply has feedback, which should prevent this kind of thing from happening.

You should trace the affected 5v rail down to the feedback pin of the controller. Then solder a little wire wherever you have a pad available on that trace (as the controller will be QFN and impossible to probe), and probe there. If the feedback voltage also drops, and the controller does not take action (which it seems it does not), replace the controller chip.

[Francisco.s]

Re: [Acer 6930G] Lower +5V problem.

Do you know if PQ14 gets abnormal temperature?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

The way i see it, this has got nothing to do with the switching transistors. It shouldn't, either - a transistor only runs in 2 states in a switching power supply: fully ON (low resistance) or fully OFF (open). So if the transistors have gone bad, it won't work at all. Besides, the power supply has feedback, which should prevent this kind of thing from happening.

You should trace the affected 5v rail down to the feedback pin of the controller. Then solder a little wire wherever you have a pad available on that trace (as the controller will be QFN and impossible to probe), and probe there. If the feedback voltage also drops, and the controller does not take action (which it seems it does not), replace the controller chip.

Hello, thank you for your answer. I just look out ISL6237's datasheet, so there is an example to use this chip for standart 5V/3.3 usage. So looks same on mainboard datasheet. In this case it's using PHASE1 (LX1) pin16 for feedback you talk about (guess). So i checked there there is really unstable votlage there. I want to say, i removed every parts i can, like LCD, Graphic Card, Wireless module etc. There is Only CPU Fan Connected. So;

First, ISL6237'S out pin, pin10(OUT1) always stable 5.07V.


when the cpu fan is running: Pin16 is like running between 1.50V - 3.2V. Changing very fast, not stable.
when the cpu fan is stopped: Pin16 running between 0V. - 1V. Not stable, changing fast.

additional information, there is PC45 connected Pin16 to Pin17(BST1);

when the cpu fan is running: PC45's other leg is like running between 4.90V - 5.80V. Changing very fast, not stable.
when the cpu fan stopped: PC45's other leg is like running between 3.0V - 4.10V. Changing very fast, not stable.


What do you think? The problem is ISL6237's itself?

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Do you know if PQ14 gets abnormal temperature?

No, there is no temperture problem.

[Francisco.s]

Re: [Acer 6930G] Lower +5V problem.

No, there is no temperture problem.

If you have a stabilized 5 volts at drain terminal of PQ14, and is not stable at source terminal, probably the voltage at gate terminal also fluctuates. (could be there is some ripple)
Try to short-circuit drain and source of PQ14, to evaluate if voltage is stabilized at both terminals.
You can not check voltage at pin 16 of ISL6237, because it is the output of a PWM circuit, so there is a square wave that should be checked with an oscilloscope.

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

If you have a stabilized 5 volts at drain terminal of PQ14, and is not stable at source terminal, probably the voltage at gate terminal also fluctuates. (could be there is some ripple)
Try to short-circuit drain and source of PQ14, to evaluate if voltage is stabilized at both terminals.
You can not check voltage at pin 16 of ISL6237, because it is the output of a PWM circuit, so there is a square wave that should be checked with an oscilloscope.

Short-circued voltage is 5.07V.

Actually, i tried to check pin25 too, ( its other phase for 3.3V i guess. i check ISL's datasheet and mainboard's datasheet it's looks like that.) So, pin25 is PHASE2(LX2) is always stable , 11v. But phase1 (pin16) is not stable. Any idea?

[Francisco.s]

Re: [Acer 6930G] Lower +5V problem.

Short-circued voltage is 5.07V.

Then, is the laptop working properly now? (as long as voltage is stable now, I mean)

But phase1 (pin16) is not stable

I think it's due to variations in the amount of current consumption of the load connected to the +5VPCU circuit.

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Guys, any ideas?... I still got nothing :\

[Francisco.s]

Re: [Acer 6930G] Lower +5V problem.

Short-circued voltage is 5.07V.

I know you can not let mosfet short-circuited forever, but I wonder if laptop runs properly that way. (with mosfet short-circuited)

[nomorebeer]

Re: [Acer 6930G] Lower +5V problem.

Thank you for your answer but, Laptop is working properly before starting voltage drops. So, when shotcuited, voltage will never drop so should work always i guess.

[Th3_uN1Qu3]

Re: [Acer 6930G] Lower +5V problem.

Thank you for your answer but, Laptop is working properly before starting voltage drops. So, when shotcuited, voltage will never drop so should work always i guess.

Sometimes it's better to address the effect than the cause. If the laptop works properly like that, leave it shorted. That MOSFET is just acting as a simple ON/OFF switch there.

Edit: You say the computer resets when trying to check MAIND. That indicates a problem there, it means that whatever is driving the MAIND signal has a very high output impedance... To drive the gate of a FET you would need a relatively low impedance source. Instead of shorting the FET you could do a more elegant solution: Pull the gate up via a 1k resistor to 5V_ALW. That should do the trick, and also have the circuit that's controlling MAIND work properly. There's a good chance that it's still able to drive the signal LOW when the computer is turned off.