Asus G751JY not turning on when touchpad is connected

[kronikus]

Hi, I don't know history of this problem. When I bought this laptop everything works fine except touchpad and buttons that are not found as hardware in device manager. Than I opened laptop and found that TP cable is missing. I ordered replacement cable, mount it and found that laptop cannot be turned on. Does not matter if any of other cables attached or not (keyboard, LED, KB light), when I connect touchpad cable, LCD remains dark, no fan spin, and after 30 seconds power button light turns off. When I unplug TP cable, everything works perfect. I don't have schematics, but I did some measurements on the touchpad board:
C1=3.2V, C2=3.2V, C3=1.4V, C4=2.9V, C5=1.8V, T19=3.2V, TV=3.2V
On motherboard, connector J3105:
Pin 1/2=3.3V
Pin 3=TP CLK
Pin 4=TP DAT
Pin 5/6=GND
Pin 7=SMB DAT
Pin 8=SMB CLK S
Pin 9=Right BTN
Pin 10=J5602 INT#
Pin 11=Left BTN

On J3105 without cable, 3.3V are present on pins 1,2,4,7,8,10

On J3105 with cable, 3.3V are on pins 1,2,4,11
Pin 8=2.7V
Pin 9=0.5V

Anyone have similar problem?

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

Anybody?

[jasko_jacker]

Re: Asus G751JY not turning on when touchpad is connected

Check If the cable Is inserted correctly (PIN 1 to PIN 1) if not solve
Probabily detective component on touchpad Board, replace It or if it's possibile only the touch chip

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

TY. The cable is correctly positioned, new and tested pin by pin. I will try to find the chip or touchpad. No luck, so far. Only possible solution there is to buy complete palmrest and it is not cheap one. And I'm affraid that there is posibility that the EC chip is bad.

[caspian]

Re: Asus G751JY not turning on when touchpad is connected

Both the KBC and the touchpad have the possibility to be defective. But a touchpad defect is more probable. before buying anything, measure resistace to GND on all pins of J3105 with and without the cable. then measure voltage on pin3 and pin4 of J3105 with and without the cable.

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

I hope that you are right. In fact, I just measured on touchpad board without connection to motherboard that SMB DAT (pin7) and V5620 INT# (pin 10) have only 2 ohm resistance to ground and 2 ohm between each other. Now I need to check motherboard but is safe to say that the touchpad controller is shorted. Chip have markings 33200D-3000 1448 BG14B01 or (BQ1).

[caspian]

Re: Asus G751JY not turning on when touchpad is connected

try replacing the chip on the touchpad. otherwise you should replace the touchpad. In that case, you should read my thread. I explained a problem that may arise if you use adhesives:
https://www.badcaps.net/forum/showthread.php?t=72757

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

Mesaured on motherboard, turned off, without attached TP cable:
Pin 1/2=3.3Vin - 250 ohm
Pin 3=TP CLK - 25 ohm
Pin 4=TP DAT - 25 ohm
Pin 5/6=GND - 0 ohm
Pin 7=SMB DAT - 4k ohm
Pin 8=SMB CLK S - 5k ohm
Pin 9=Right BTN - 9M ohm
Pin 10=J5602 INT# - 10k ohm
Pin 11=Left BTN - 9M ohm

As I can see, signals on both pins without attached cable are about 80mV amplitude on about 30kHz.

Does that 25 ohm and that signals on TP CLK and TP DAT seems ok or I must borrow scope to further test?
TY

[caspian]

Re: Asus G751JY not turning on when touchpad is connected

The 25 ohms resistance is two low. It seems KBC is defective. it will be better to use an ordinary mouse instead of the touchpad. This is due to the fact that replacing Both KBC and touchpad is costly and time consuming.

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

What confusing me is fact that pin4 also have 25 ohm resistance to ground but 3.3V is present all the time when laptop is on. On touchpad board "only" SMB DAT and INT# are shorted. TP DAT and TP CLK are not.
1. Is that 3.3V normally "generated by KBC" and, because of KBC fault, pulled down by short in KBC itself? If it is - how would be possible for laptop to work, even without TP attached?
2. Or that 3.3V is genereated by system +3VS, than pulled down by KBC if certain conditions are not met? It seems more likely for me - but I'm maybe very wrong?
3. How can I even know that 3.3V has to be present on that pin...
3. Can I just lift up D3110 ESD protection diode chip and 4.7K ohm RN 4043 resistor array to isolate that specific KBC TP CLK signal from rest of board and than measure? I have to find datasheet for KBC.

[SMDFlea]

Re: Asus G751JY not turning on when touchpad is connected

Can you take a picture of the whole touchpad pcb area .

[caspian]

Re: Asus G751JY not turning on when touchpad is connected

3. Can I just lift up D3110 ESD protection diode chip and 4.7K ohm RN 4043 resistor array to isolate that specific KBC TP CLK signal from rest of board and than measure? I have to find datasheet for KBC.

yes, this is going be a good test. Do it and measure the resistance again.

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

Can you take a picture of the whole touchpad pcb area .

Here it is. This picture origins from internet but it's same as my board.
Chip is marked as 33200D-3000 1448 BG14B01 or (BQ1)

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

yes, this is going be a good test. Do it and measure the resistance again.

Firstly I unpluged the battery, than removed D3110 diode chip and measured resistance. Both TP CLK and TP DAT now was about 7k ohm to ground, same as SMB CLK and SMB DAT.
RN 4043 resistors are both 4.7k ohm as stated on boardview. CORE_PWRGD to 3.3VS resistor R5802 are 2k ohm, also.
BUT - one important thing that I didn't mentioned before!
I measured 7k ohm without battery or charger!
When I connected the battery, resistance without D3110 was same as before - on TP CLK and DAT both 25 ohm to ground. And voltages are same: 3.3V except on TP CLK.
Is it safe to think that TP CLK line is not shorted, and 3.3V is pulled down by KBC for other reasons, maybe absence of touchpad?
I don't have spare TP to try and used palmrest costs 80$. Is it worth to try?

[SMDFlea]

Re: Asus G751JY not turning on when touchpad is connected

You could replace D3110 first as the cheapest option, also check caps C3-C5 on the touchpad,trace where pin 3 goes. A replacement part if you can`t get the AZC099-04SP is NXP PUSB2X4D

https://cdn.badcaps-static.com/pdfs/...ce364ce715.pdf

[kronikus]

Re: Asus G751JY not turning on when touchpad is connected

[QUOTE=SMDFlea;891334]You could replace D3110 first as the cheapest option, also check caps C3-C5 on the touchpad,trace where pin 3 goes. A replacement part if you can`t get the AZC099-04SP is NXP PUSB2X4D

On motherboard without touchpad connected:

Difference between measuring TP CLK and TP DAT resistance to ground are dependent only on presence or absence of power supply (laptop not tuned on). Without battery or charger resistance is about 7k ohms. When battery or charger is present, resistance is 25 ohms. When turned on, on TP DAT voltage is 3.3V, on TP CLK is 15 milivolts.

On touchpad, when not connected to anything:

SMB DAT and V5620 INT# have only 2 ohm resistance to GND.
All other resistances are in kiloohms or even in megaohms.
All capacirtors are OK, resistor is OK.
Maybe is better visible on picture.

There are no difference with or without D3110. Difference is only when power is applied, regardless of D3110.