ASUS TUF Dash Motherboard FX516 REV 6.0 Model Device Not Charging

[lazenes]

So the adapter IS being announced correctly to the EC.

Confirm again if you have a voltage for MB_MAX_POWER. According to the v4.0 schematic, the high side resistor should also be @ ~3v since it is tied to +3VACC.

If no voltage, remove all power. Meter in resistance mode. Measure the resistance between the top side of PR8935 to top side of PR8937. Best to test each side of these parts to confirm if one combination is ~0 ohms. That is, each high side resistor should be mated to be +3VACC. From earlier checking, the MB_MAX_POWER was @ 0v.

I measured the resistors as you suggested (board fully powered off, meter in resistance/diode mode):

PR8935 (top side): red probe on top = OL, reversed = ~13.58 kΩ

PR8937 (top side): red probe on top = ~12.70 kΩ, reversed = OL

Between PR8935 top ↔ PR8937 top: red probe on PR8937 top & black probe on PR8935 top = ~12.70 kΩ

Between PR8935 bottom ↔ PR8937 bottom: red probe on PR8937 bottom & black probe on PR8935 bottom = no reading (OL). When reversed, I get ~13.58 kΩ.

So neither side of these two resistors is showing ~0Ω continuity to each other or to +3VACC**

[lazenes]

When I measure the MB_MAX_POWER line, it goes to 3V as soon as the device powers on, not 0V. So, there is no voltage before starting. I also observed this condition on the pins of PR8935 and PR8937.

[mon2]

MB_MAX_POWER is the signal that is between the pull-up (PR8935) and the pull-down (PR8936) resistor. This voltage should be lower than 3v3 if this resistor based voltage divider is working properly.

MB_MAX_POWER is 3v3 when you power on? This is too high if accurate.

Remove all power. Measure the resistance across resistor PR8935.

[lazenes]

Edit: You misunderstood. It's not the MB_MAX_POWER value.
Measured voltages with the board powered on:

• PR8935 = 1.8V
• PR8936 = 1.8V
• PR8937 = 3.3V

[mon2]

Attach the power adapter. Measure the voltage to ground of each pin on PD8907.

[lazenes]

When I measured it with only the battery and both connected to the motherboard, I only read a value of 0.14V on the 1. pin.

[mon2]

Flux and remove PD8907 off the board. Do not lose this dual diode. Test again without this part.

[lazenes]

Flux and remove PD8907 off the board. Do not lose this dual diode. Test again without this part.

So you mean I should remove PD8907 and then test again with the battery and adapter connected?
I measured the part with the multimeter in the diode position. When I placed the red probe on the lower legs, I read a value of 0.216 on both legs
.

[mon2]

Yes. It will be a quick test. Remove the part. Test with only the adapter first. I am suspicious of the connector pin inside the adapter connector which mates to the common cathode (single pin on this part).

[lazenes]

Yes. It will be a quick test. Remove the part. Test with only the adapter first. I am suspicious of the connector pin inside the adapter connector which mates to the common cathode (single pin on this part).

Test result after removing PD8907:
With only the adapter connected (no battery), I measured 2.59V on pin #1 of the pad where PD8907 was located.

[lazenes]

Yes. It will be a quick test. Remove the part. Test with only the adapter first. I am suspicious of the connector pin inside the adapter connector which mates to the common cathode (single pin on this part).

Test result after removing PD8907:
With only the adapter connected (no battery), I measured 2.59V on pin #1 of the pad where PD8907 was located.

[mon2]

Ok. Does the board power on without the battery? Attach the battery, does the battery charge?

If not, measure the voltage to ground on the battery connector. This voltage should be slightly higher than the voltage marked on the battery pack labels.

Another recent thread noted a similar case where the root cause was the high side mosfet on the battery charge circuit was leaking. This resulted in ~19v appearing on the battery connector which is too high.

[lazenes]

After removing the part from the board, the behavior is still the same. The battery does not charge. The board only powers on with the battery attached, but it still does not charge.
No, the battery voltage is 15.6. This voltage remains constant whether I plug the battery into the motherboard or connect the adapter, meaning it is not charging. The battery connector is not receiving 19v or a similar voltage.
Should I replace the circuit component PD8907?

[mon2]

What is the voltage to ground of AC_BAT_SYS (with only the adapter connected)? What is the voltage with both, the adapter and battery connected?

Remove all power. Meter in resistance mode. Measure the resistance directly on the charger IC for the ACN & ACP pins. One probe on ACN; other on ACP. Checking the current sense circuit full path resistance for the main power rail.

A very long thread of complaints on this model with the same symptoms.

https://www.reddit.com/r/ASUS/commen...s_not_turn_on/

[lazenes]

What is the voltage to ground of AC_BAT_SYS (with only the adapter connected)? What is the voltage with both, the adapter and battery connected?

Remove all power. Meter in resistance mode. Measure the resistance directly on the charger IC for the ACN & ACP pins. One probe on ACN; other on ACP. Checking the current sense circuit full path resistance for the main power rail.

A very long thread of complaints on this model with the same symptoms.

https://www.reddit.com/r/ASUS/commen...s_not_turn_on/

When I measure the ACN and ACP pins connected to PC8902, I get 0 ohms. However, when I connect the charger, I read 20.4V on both pins I think it's a short circuit AC_BAT_SYS voltage is 20.4v

[mon2]

There is a very small resistance between ACN & ACP, by design so the measurements are correct.

Carefully measure the voltage to ground of ILIM pin #21 on the charger IC. This value defines the current value to be used for the battery charge function.

[lazenes]

I just measured the voltage to ground of the ILIM pin #21 on the charger IC, and I'm not getting any voltage reading on pin #21.

[mon2]

Carefully measure the voltage to ground on PR8913. Test both sides of this resistor. One side must be the +3VA voltage.

Correction on resistor #.

[lazenes]

Carefully measure the voltage to ground on PR8913. Test both sides of this resistor. One side must be the +3VA voltage.

Correction on resistor #.

I measured PR8913, and you're right: one side measures +3.3V, but the other side measures 0V.

[mon2]

Remove all power. Measure the resistance across PR8913. Is the resistance close to the schematic value? If yes, measure the resistance to ground of the point with 0R ohms. Either the PR8913 resistance is too high or there is a short on this line. From the board view diagram, there should be a voltage here.