Acer V5-531 Does not turn on

[Mad Capper]

Attached are the motherboard schematic and boardview and a datasheet for an IC. Change .doc to .GR for boardview file.

Never had a problem with it until now. The laptop would turn on if put to sleep but when shut down it would not turn back on. I have another of the exact same laptop so I switched chargers and batteries to see if that worked. It did once after many swaps and power button presses. I am not sure the combination that worked but it did not seem to do it immediately, i.e. I just kept swapping over and over until it came on. When I put it to sleep again or shutdown, I can't remember which, it did not turn back on even with swapping things.

I am new to laptop motherboard repair and laptop schematic reading but think I have traced it to some potentials I hope someone with more experience can give a more definitive diagnosis. As I have a working one of these motherboards I compared the things that I thought were relevant and came up with the following. Please correct me where I may be wrong. GOOD AND BAD signifies which motherboard not necessarily whether that component is actually bad or giving differing reading do to it being bad or another component inducing the differing reading.


Measurements for pins not listed were taken but not included here as they were the same or very close. When follwing the schematic I hope the below testing shows me tracing the problem. I am uncertain which of the first three components are the sole cause of the problem or if there are multiple component failures or if it is something else.

Super I/O
...GOOD U2701..........BAD U2701
Pin 14......0V...................3.3V

The schematic seems to indicate that pin 14 S5_ENABLE is an output and originates from here. If so then I do not know if this means there is an internal short and 3.3V is coming out or elsewhere down the line 3.3V is being fed back to it.

Dual MOSFET
GOOD PQ4101 .......... BAD PQ4101
1....GND......................GND
2....0V.......................3.3V
3....4.73V....................0V
4....GND......................GND
5....0V.......................3.3V
6....4.97V....................0V

When the GOOD board is turned on the readings are the same as when the BAD board is off and plugged in. I do not know where the 5V on pins 3 and 6 of PQ4101 comes from if pins 1 and 6 of PU4103 are input.


Power supply Controller
GOOD PU4103..........BAD PU4103
1....5V....................0.9V

I can feel this IC getting warm and if I put some isopropyl alcohol on this IC I can see that the alcohol evaporates quicker due to the heat whereas it does not on the GOOD board. According to the pinout in the attached PDF datasheet for this component it says that pin 1 and 6 are inputs.

GOOD AFTP12 S5_ENABLE..........BAD AFTP12
.........0V...........................3.35V

............GOOD R3603.......... BAD R3603
1...S5_ENABLE...0V.....................3.3V
2...5V_S5_EN....0V.....................3.3V

GOOD D3601..........BAD D3601
1...0V...................3.3V
2...0V...................0V

GOOD RN2705 BAD RN2705
1...3.3V...............0V
2...3.3V...............0V
3...0V.................3.3V

GOOD R2780..........BAD R2780
1...3.3V.................3.3V
2...3V...................3.3V
Both resistors measure 9.89K



I hope that gives a good, correct and accurate overview of the not turing on issue. Again, I think the problem is with one of U2701, PQ4101, PU4103 or maybe a combination or something else entirely. If someone is able to trace my work through the schematic and offer some insight and assistance it would be appreciated.

Thank you

[Sephir0th]

Re: Acer V5-531 Does not turn on

Would you explain for me, what do you mean with "swapping"? Do you mean opening and closing the Lid?Sorry, my english is far away from perfect...

[Mad Capper]

Re: Acer V5-531 Does not turn on

I took the AC power supply and battery from the working laptop and used them on the non-working laptop to see if those were the problem. An easy initial test to rule them out.

I would plug in the power supply or battery and try to turn on the computer. I did this a few times with each battery and power supply, in various combinations. It worked once but I think it was just a coincidence. The power supply and battery work fine in the known good laptop. So the problem lies on the motherboard.

[Sephir0th]

Re: Acer V5-531 Does not turn on

No Idea If i Understand your Problem completely, but as far as i Understand i Would Check the Power Button itself First. Is there Voltage on KBC_PWRBTN# when trying to Power it on and is it going to 0V when you Press it?

[Mad Capper]

Re: Acer V5-531 Does not turn on

I am getting 3V on pin 3 of PWRCN1 on both machines. I have removed the ribbon cable and power button from the non-working computer and it works fine on the working one.

[Sephir0th]

Re: Acer V5-531 Does not turn on

So i believe the Problem is somewhere between Pressing the Power Button and S5_ENABLE. These are Only 2 Steps in the sequence (Page 99).

To be honest, i'm Not really experienced in hunting for logical Signals. But My next step Would be to Check the Voltages on Q2703 on Gate, Source and Drain. We want to be Sure the Enable Signal for KBC is there and the Transistor is working properly.

I guess we're Not far away from the Culprit.

[Mad Capper]

Re: Acer V5-531 Does not turn on

There is no component at location on the board.

In what I have done so far when the schematic says there is no component at a location my board matches up. This one is a discrepancy.

The schematic is for the closest I could find. The schematic is for Petra UMA MB 11324 Revision -1 PCB P/N 48.4VM02.001

My mother board is 11324-1 48.4VM02.011

So not very far off, but a few slight differences.

I believe the problem is before the Power Switch Logic part of start up. I believe the problem is related to the fact I do not have the correct voltages when off where they should be as shown in my comparison of the good and bad boards.

I believe that the problem is somehow related to the first three components I mentioned. I am having difficulty understanding whether some are input or outputs and how that relates to the measurements I mentioned.

[Sephir0th]

Re: Acer V5-531 Does not turn on

Ok... anyone Here can correct me, If this is wrong:

For 5V_PWR_ENABLE (PQ4101) and 5V_PWR_Entrip (PU4103) Signal you NEED working S5_ENABLE before! And i try to find Out If there is another Signal Missing before, If it isn't clear right now.

So you decide If we Go through this or If you want to be stuck at this components.

[Mad Capper]

Re: Acer V5-531 Does not turn on

I agree I need S5_ENABLE. From my reading of the schematic it originates from pin 14 of U2701 and should be 0V as per my good board. As it is 3.3V I do not know if there is an internal short in U2701 or 3.3V is being fed back to that pin because something else is faulty.

I do not know what the sequence between these three components I mentioned is. One could be faulty causing the readings I am getting or perhaps multiple are faulty.

Are pins 1 and 6 of PU4103 supposed to be outputs of 5V that go to PQ4101 pins 3 and 6 and thus make pins 2 and 5 0V, for correct operation? And because 5v is not coming out that allows pins 2 and 5 to let 3.3V pass to pin 14 of U2701, thus not allowing startup.

I do not believe as though I am putting undue emphasis on these components. I believe this is where the problem may lie. This is where the differences in my testing of the good and bad board are and it points to them being part of the problem. Perhaps, there is something that is not these components that is causing them to measure as they do but I have yet to find it, thus my focus on them.

Some updated readings
Power supply Controller
GOOD PU4103..........BAD PU4103
1..........5V....................0.9V
6..........5V....................0.9V
19.........0V...................5V

[SMDFlea]

Re: Acer V5-531 Does not turn on

Test voltage on PU4103 pin 8 and 17

[Sephir0th]

Re: Acer V5-531 Does not turn on

I had to think about this sentence:

"When the GOOD board is turned on the readings are the same as when the BAD board is off and plugged in."

Maybe every time it don't Turn Off properly and this is the reason why it don't come Back to life. But normally this can't be the Case, because you swapped battery and Adapter between the Laptops...

We can Test this. Has the board a Coin cell or is it integrated in the Battery? If there is a Coin Cell, then unplug Adapter, Battery and Coin Cell too. Short the PINs of the Coin-Cell Connector for at least 20 Seconds with a tweezer, screwdriver or similar. After that Plug all Back and try to Power it on. If it works, i believe we have an issue in the shut down sequence.

PS: And Check the Voltage of the CMOS Coin cell. Should be above 3V.

[Mad Capper]

Re: Acer V5-531 Does not turn on

CMOS battery is a coin cell at 3.12V

I did what you suggested and it has no effect. The condition is still the same.

To be clear I was only referring to PQ4101 when saying that the GOOD board voltages when turned on were says as the corresponding component on the BAD board when off. I did not check other component voltages when the GOOD board was turned on. I just happened to note this during my testing and mentioned it as it seemed interesting to have the same reading when one was on as the other off.

[Sephir0th]

Re: Acer V5-531 Does not turn on

Ah okay, so this was a misunderstood. So do as advised by SMDFlea. It seems He Has an Idea.

[Mad Capper]

Re: Acer V5-531 Does not turn on

Yes, I have the VREG 3V and VREG 5V outputs

GOOD PU4103..........BAD PU4103
8...........3.38V.................3.37V
17..........5V....................5.04V

All PU4103 readings are the same on GOOD and OLD +/- for all pins except the following

GOOD PU4103..........BAD PU4103
1..........5V....................0.9V
6..........5V....................0.9V
19.........0V...................5V

Are pins 1 and 6 input or output?

[Sephir0th]

Re: Acer V5-531 Does not turn on

Back to Q2703. Pls Share a high quality Photo of this Area, so i can Understand how this Rail could work without the P-Channel Mosfet.
Please do the Voltage Measurements on the empty Pads of Q2703 and Show them in the Picture.

Please Tell us the voltages of this area from the working Board too.

[Mad Capper]

Re: Acer V5-531 Does not turn on

Here is the information you requested. Can you explain to me how this is relevant, I do not understand. I do not know how it works without it but it does.


GOOD Q2703..........BAD Q2703
1..........3.3V.................3.3V
2..........0V....................0V
3..........3.3V.................3.3V

Q2703 is in the upper right hand corner of the image to the upper right of the Super I/O

[Sephir0th]

Re: Acer V5-531 Does not turn on

Hehe, this is for me a Challenge too. I'm still learning.

I wanted to Check If the EC_Enable# Signal is Coming Out and driving the 3D3V_AUX_KBC (3.3V LDO) through this Not existing mosfet to make it to 3D3V_S5.

The Problem i have is, your measurements are Not getting much Sense e.g. You shared 3 Measurements from PR2705 but is has 4 Pins. I believe you Mean with Pin 3 the Input (3D3V_KBC_AUX), but Maybe i'm wring. Another one is Q2703. Yes, it has 3 Pins, but they are Called S, D, and G (Source, Drain and Gate) and are Not Marked with Number on the PCB. For this reason it is Very hard to Follow. Would you clarify this for me? Otherwise the variables are to many to find the Culprit.

Edit: Additionally one Thing. What is this beetween PIN 12 and PIN 13 of the EC? Are The Pins shorted? Check this Please.

[Mad Capper]

Re: Acer V5-531 Does not turn on

There is no component PR2705, do you mean RN2705?

Sorry copy/paste missed pin 4. Also I re-measured, disregard original measurements for RN2705 and use these.

GOOD RN2705 BAD RN2705
1...3.3V...............3.3V
2...3.3V...............3.3V
3...0V.................3.3V
4...3.3V..............3.3V

See boardview file for Q2703 pin assignments and reference schematic. Starting at 3 o'clock position going anti-clockwise pins are 1(D, 3DV3_AUX_KBC), 2(G, EC_ENABLE#), 3(S, 3DV3_AUX_S5 )

By EC I assume you mean U2701 the Super I/O and are referring to the photo. It was just a piece of dust.

[Sephir0th]

Re: Acer V5-531 Does not turn on

There is no component PR2705, do you mean RN2705?

Sorry copy/paste missed pin 4. Also I re-measured, disregard original measurements for RN2705 and use these.

GOOD RN2705 BAD RN2705
1...3.3V...............3.3V
2...3.3V...............3.3V
3...0V.................3.3V
4...3.3V..............3.3V

You See, i'm actually confused, so yes i mean RN2705...

And you See too, we have different measurements on PIN1 & PIN2. This has been also my next step to Double-Check this. So i assume, this Resistor is working fine.

So what can we say now? S5_ENABLE is the First Missing Signal Here for Sure. Why is it Not Coming Out?

Check this Rail for short to ground and compare with the working one (with all Power removed). If there is No difference, i think your EC (SIO) is Bad. Maybe reprogramming Would Help. Anyway, do the following step Just to be Sure:

If there is difference beetween the Rails, Double Check your Voltage measurements on D3601 First, please. Then Check D3601 in Diode Mode in both directions and R3602/R3602 in Ohms Mode for correct value. Compare with the working Board. And do the measurements with all Power removed.

Maybe we're Not going the fastest way but i'm Sure we'll find the Bad component soon...

PS: I do all this from mobile Phone, so No able to Open Boardview right now. It's Winter Holidays here and my daughter wants my attention...

[Mad Capper]

Re: Acer V5-531 Does not turn on

There is not a different measurement on pin 1 and 2 of RN2705 from one board to the next. It was an error in my original post. Again, go with the current information you quoted.

We knew something was wrong with S5_ENABLE from my first post. As seen from from the S5_ENABLE test point.

GOOD AFTP12 S5_ENABLE..........BAD AFTP12
............0V....................................3.35V


D3601 on BAD board checks out good, same as on GOOD board. I have included the measurement again and added pin 3.

GOOD D3601..........BAD D3601
1...0V...................3.3V
2...0V...................0V
3...3.3V.................3.3V

R3603
GOOD R3603..........BAD R3603
........2K..................1.997K
1......0V...................3.3V
2......0V...................3.3V

I do not believe there are any shorts. I am not certain exactly what to test, but everything I check in terms of potential shorts to ground, as best as I can tell, there is nothing different between the boards.

Yes I think the SIO U2701 could be bad but also or only PU4103. I do not believe the SIO on this board has the BIOS in it so I don't believe there is anything to program.

As I see it there is 3.3V in places where it should be 0V. The question is why is this occurring. Is pin 14 of U2701, the S5_ENABLE, supposed to be an output or an input? Is pin 1 and 6 of PU4103 supposed to be inputs or outputs? PQ4101 on both boards checks the same in diode mode, but the measurements are wrong on the BAD board. Does this all stem from PU4103? I would think the fact that it is getting hot when it shouldn't would be a good indicator that it is bad. Again, I do not know if it is bad or the readings and heat are because of something else, e.g. the SIO.

Can you tell me your opinion of whether the pins I mentioned on U2701 and PU4103 are inputs or outputs? Also, why do you suppose pin 19 of PU4103 is 5v when it should be 0V? I speculate according to the block diagram in the datasheet that there is some internal short or the like.

I appreciate your assistance. Spend time with the family, they are more important than this.