Asus FX504G no power

[madjid911]

Hi, I have an asus laptop FX504G (dabklgmb8d0 rev D) that does not start at all, no signs of life, no liquid damage, no shorts, the processor, the graphics card, the chipset and the SIO micro controller have good resistance.


I have 20V everywhere, on the other hand the SIO micro controller is not powered, there is no +3V, so I changed the "5X=" chip which was not short and well supplied with 20V, the result remains the same, looking at the diagram I see that EN1 and 2 is "S5_ON" (he is at OV), it is a signal that must come from the SIO, isn't it? But then what is the chip that generates the +3V to supply the SIO ? I'm looking but I can't find it, I'm not an expert, if you can help me please



Schematic and BRD : https://www.badcaps.net/forum/troubl...heamtic-please

[mon2]

Check PU28 - REG3 rail. This low current LDO rail powers the SIO. Search for the same netname of '51225_LDO3' to locate the power path.

Do you have a stable voltage here? If not, test the resistance to ground (without power to the board) of this 51225_LDO3 to determine if there is a possible short on this line.

[madjid911]

Check PU28 - REG3 rail. This low current LDO rail powers the SIO. Search for the same netname of '51225_LDO3' to locate the power path.

Do you have a stable voltage here? If not, test the resistance to ground (without power to the board) of this 51225_LDO3 to determine if there is a possible short on this line.

Thanks for the details, I have 3V26 on 51225_LDO3, is it 51225_LDO3 that should power SIO or +3V?

[madjid911]

would that mean my SIO is dead? When I press the power button I don't have the 3v and 5V that triggers, I tried with another keyboard too

[mon2]

No. We only know that it is not being powered.

See attached. Do you have a resistor stuffed @ PR443? It may be a no-stuff in the bill of materials so asking here.

Once you locate the PCB pads for PR443 -> test the voltage to ground on each leg of this part. One side should offer the 3v3 from the LDO you have measured and so should the other side of this small circuit.

What is the voltage to ground of each pin of PQ69?

[madjid911]

No. We only know that it is not being powered.

See attached. Do you have a resistor stuffed @ PR443? It may be a no-stuff in the bill of materials so asking here.

Once you locate the PCB pads for PR443 -> test the voltage to ground on each leg of this part. One side should offer the 3v3 from the LDO you have measured and so should the other side of this small circuit.

What is the voltage to ground of each pin of PQ69?

PR443 pin 2 : 4,5 ohms, 0V
pin 1 : 55,2komhs 3V28

PQ69 pin 2 : 1V3, PIN 3 : 2V6
PQ63 pin 1 : 3V26; pin 2 : 2V74; pin 3 : short

so I have shorts on +3VPCU ? should I put voltage on it to know where it heats up?

[madjid911]

No. We only know that it is not being powered.

See attached. Do you have a resistor stuffed @ PR443? It may be a no-stuff in the bill of materials so asking here.

Once you locate the PCB pads for PR443 -> test the voltage to ground on each leg of this part. One side should offer the 3v3 from the LDO you have measured and so should the other side of this small circuit.

What is the voltage to ground of each pin of PQ69?

I injected voltage on +3VPCU, the SIO IT8987E heated up, I removed it, I no longer have a short circuit, so I have to order a new one, can you tell me if the SIO IT8987E is programmed? Can I buy a blank one?

I have a new SIO IT8528E, IT8587E and IT8518E in stock, can this be compatible?

[madjid911]

I ordered a new programmed sio, it works, thanks for your help

[mon2]

Well done! Appreciate the closure for this case.