ASUS GA401QM No ACDRV, No CMSRC

[mon2]

Is the battery connected? The ACN side may be having the battery voltage which is fed through the internal steering diode present inside of battery mosfet @ PQ8903.

The purpose of ACP / ACN on every regulator is to gauge the voltage drop from INPUT (ACP) to OUTPUT (ACN) legs. The voltage drop is minute in magnitude due to the very small resistance across these 2 points being measured. This is intentional. Too much resistance will cause a massive voltage drop and also generate heat.

The resistor's resistance is expected by the designers of this charger IC and the design team who built this PCB. Respectively, using SMBUS commands, the host (SMBUS master) can read out the voltage drop across these 2 test points and from the voltage drop, can gauge the amount of current being drawn by the downstream (consumer side) of this power rail. If the ACN side is 0 volts or much lower than ACP, then the charger will detect this fault and act accordingly. In general, ACP / ACN should be extremely close in voltage to each other.

[ResoluteHawk]

No battery is connected. This was with just the charger plugged in.

[mon2]

May be due to the internal steering diode @ PQ8901. Measure the voltage to ground @ PL8901. Compare to the ACN to ground voltage.

[ResoluteHawk]

PQL8901 measures 0.215V.

ACN voltage is now 7.3V at Pin #2 but still 4.3V at the current sense pin.

This is with just the charger with current sense resistor desoldered.

Something else must be wrong here.

I don't have the wire with me and I'll have to bring it with me tomorrow, but even if I were to solder a wire from ACN on the capacitor and connect it to ACN at the current sensor, wouldn't we still only get 7.3V?

[ResoluteHawk]

Does anyone have any other ideas on how I can fix this? Maybe there's something we're missing?

Is it ok if I just run a wire from ACP directly to the current sense ACN? I don't know if it's a good idea for two pins to be soldered to the same connection point.

[mon2]

Is it ok if I just run a wire from ACP directly to the current sense ACN?

No. You will be defeating the current sense feature of the design since the ACN voltage will match the ACP voltage. The whole premise of the current sense resistor is to allow for the voltage drop between ACP and ACN inputs. From this voltage drop, the current draw can be calculated by the charger IC. With no voltage drop, all will appear to be peachy.

[mcplslg123]

Post a clear picture of charging IC and CLR area. Fist check whether the capacitor between ACN/ACP line buzzes when measured in diode mode? If not, then check continuity from ACN pin to both sides of this cap-this way we can be sure the trace break problem is near to charging IC or near CLR.
If the continuity is ok between ACN/ACP pins and cap, then repeat the same test from cap to CLR.

[mon2]

Same case and resolution here:

https://www.badcaps.net/forum/troubl...blem-hp-255-g8

[ResoluteHawk]

Thanks for your help mon2!

I soldered a jumper wire from the capacitor directly to the current sense resistor and plugged in power.

Board powers on just fine now.

Even though this wire is enameled, I'm going to replace it with a wire that has red plastic sheathing just to be sure nothing shorts out over time. Also a red wire will look better with the board.