Asus FX86F freeze with Charger

[salawayon]

help needed on this unit. it freeze when charger is being inserted. but with just the main battery only it works normal. with charger inserted at bootup it will end up in BSOD. i tried already flashing the bios... thanks

[mon2]

Re: Asus FX86F freeze with Charger

Check the usual 2 x DCin mosfets that follow the DCin power adapter connector.

If you have schematics for this unit, link or post them here.

If not (have not checked my database of schematics), locate the DCin connector and search for the usual 8 pin (small black square looking package) mosfets.

Post clear pictures here for a review. You can check the status of these mosfets by removing all power (NO BATTERY either) and check the resistance across the mosfet pins.

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement and also the scale used on your meter.

[salawayon]

Re: Asus FX86F freeze with Charger

i already replaced those two mosfets before posting here.
original mosfets - 4511NH
replaced with - MDU1516 and MDU1511
got same unit but it uses AO6414A mosfet.

[mon2]

Re: Asus FX86F freeze with Charger

The MDU and AO parts are N-channel (single) and appear to be fine for replacements.

So far, unable to locate the datasheet for the 4511NH mosfet. Your logic board is 100% identical that uses the AO ?

Check the voltage on each pin of each mosfet:

source (1-2-3)
gate (4)
drain (5-6-7-8)

with the adapter connected. Being N-channel, the gate voltage is expected to be ~25v to enable the respective mosfet.

Update - forgot to ask - what is the charger IC on this logic board? It should be nearby. Perhaps the TI ('BQ') series ??

[mcplslg123]

Re: Asus FX86F freeze with Charger

Does it uses NEC-Tokin caps on cpu vcore circuit??

[salawayon]

Re: Asus FX86F freeze with Charger

The MDU and AO parts are N-channel (single) and appear to be fine for replacements.

So far, unable to locate the datasheet for the 4511NH mosfet. Your logic board is 100% identical that uses the AO ?

Check the voltage on each pin of each mosfet:

source (1-2-3)
gate (4)
drain (5-6-7-8)

with the adapter connected. Being N-channel, the gate voltage is expected to be ~25v to enable the respective mosfet.

Update - forgot to ask - what is the charger IC on this logic board? It should be nearby. Perhaps the TI ('BQ') series ??

@mdu1516:
source - 19.85v
gate - 24.92v
drain - 19.85v

@mdu1511:
source - 19.84v
gate - 24.93v
drain - 19.84v

it uses BQ24780s as charging IC.

[salawayon]

Re: Asus FX86F freeze with Charger

Does it uses NEC-Tokin caps on cpu vcore circuit??

it doesn't have a NEC-TOKIN Caps

[mon2]

Re: Asus FX86F freeze with Charger

These are good readings. Locate the other mosfets mated with the same charger IC. Need to check the resistance of their pins to be sure they are not defective.

Review the battery mosfet, which may be leaking.

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

[salawayon]

Re: Asus FX86F freeze with Charger

schematics and boardview:

https://www.badcaps.net/forum/showth...hlight=FX505GD

[mon2]

Re: Asus FX86F freeze with Charger

Excellent. Thanks for the link.

Review the resistance of Q8800.

Remove all power and no battery before taking measurements.

[salawayon]

Re: Asus FX86F freeze with Charger

@Q8800 resistance with respect to ground.
drain - 1.5Mohms
gate - 638Kohms
source - 3.4Mohms

voltages @Q8800:
ON BATTERY:
source - 11.94v
gate - 8.04v
drain - 11.94v

ON CHARGER ALONE:
source - 12.67v
gate - 12.66v
drain - 19.96v

WITH BATTERY and CHARGER connected:
source - 12.92v
gate - 12.62v
drain - 19.72v

[mon2]

Re: Asus FX86F freeze with Charger

Resistance check, not to ground but across the mosfet pins.

From post #2

check the resistance across the mosfet pins.

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement and also the scale used on your meter.

[salawayon]

Re: Asus FX86F freeze with Charger

sorry for that... i used FLUKE 75 multimeter...
* with mosfet removed from board all resistance reading were infinite...
* with mosfet while onboard:
source-drain = 262Kohms
source-gate = 1.7Mohms
gate-drain = 2Mohms

[mon2]

Re: Asus FX86F freeze with Charger

With this battery mosfet removed, does the charger continue to power the logic board properly? That is with NO freezing if using only the power adapter?

Removing the battery mosfet will remove the battery as a power source from the equation unless the high side mosfet of the charger is leaking.

[salawayon]

Re: Asus FX86F freeze with Charger

without Q8800 mosfet:
- on battery alone the unit is ok.
- with charger alone unit is working but it freeze at startup
- on battery at normal startup but when charger is being used it freeze

[mon2]

Re: Asus FX86F freeze with Charger

With battery alone, the battery mosfet Q8800 is removed but the logic board works??

If yes, replace the high side charger mosfet as it must be leaking. Check the resistance like before of the high side mosfet. No battery or adapter during these checks.

With Q8800 removed, the logic board should not be powering up with only the battery.