Asus EEPC 1000HD (904HD 1.3G) nie działa z zasilacza i nie ładuje baterii

Dzień dobry.
Mam laptopa z płytą jak w tytule. Nie działa na zasilaczu ani nie ładuje baterii. Na baterii pracuje poprawnie. Wykrywa podłączenie zasilacza w systemie Lubuntu.
Sprawdziłem:
LM393 (PU602):
Pin 1 - 300mV (opór do masy na tym pinie wynosi 500kOhm i rośnie, również na wylutowanym LM393)
Pin 2 - 4.67V
Pin 3 - 5V

Charger (PU600A)
Pin 1 - 12V
Pin 24 - 12V
Pin 4 - 1.43V
Pin 5 - 690mV

RT8203 (PU400)
Pin 20 - 1V

Usunięcie LM393 (PU602) i połączenie jego pinu 1 z pinem 8 powoduje że laptop ożywa - uruchamia się na ładowarce (nawet bez baterii) oraz ładuje baterię poprawnie.
Wymieniałem LM393 na sprawne i brak poprawy.
Gdzie jeszcze szukać przyczyny takiego zachowania?

Hello!

Check the resistor PR638 (1MΩ) and check if 19V is present on pin 1 of this resistor.

matic napisał(a):check if 19V is present

I assume you mean 12V Yes, proper voltage is present.

Also, i checked resistance of PR637, PR639, PR636, PR638, PR623 off the board - all good.
Checked voltages and resistances to ground on pins 3, 2, 1 of PU602 with PC624 off - no change.

I've tried removing PQ603 to perform more measures, but it end up flying off my tweezers. Since I repair that laptop for my own collection i end up bridging pins 6 and 4 of PQ603. Works properly now. Just need to remember to use 12V only chargers from now on.

If anyone still has some helpful ideas what i could yet measure to properly fix it, im open.

AveoCross napisał(a):I assume you mean 12V Yes, proper voltage is present.

Yes, sorry my fault. The power supply for this machine is 12V.

AveoCross napisał(a):LM393 (PU602):
Pin 1 - 300mV (opór do masy na tym pinie wynosi 500kOhm i rośnie, również na wylutowanym LM393)

The voltage to ground on pin 1 of chip PU602 should be 6V (also with the chip PU602 removed from the board).
Possible causes: damaged PR638, PR639, PC624, PQ603 or damaged copper trace on the PCB.

Remeasure this voltage with the PU602 and PQ603 removed from the board. If you still don't get 6V, also remove the capacitor PC624 and check this voltage again.

AveoCross napisał(a):I've tried removing PQ603 to perform more measures, but it end up flying off my tweezers.

You can replace this transistor for example with 2N7002KDW or L2N7002DW, which is usually easier to find on some scrap board.

matic napisał(a):The voltage to ground on pin 1 of chip PU602 should be 6V (also with the chip PU602 removed from the board).
Possible causes: damaged PR638, PR639, PC624, PQ603 or damaged copper trace on the PCB.

I figured it should be 6V before, from voltage division on resistors. Thats why i measured related resistors off the board, measured resistances do ground with and without PU602 and PQ603 and PC624 (that one i also measured off the board - its ok) (sorry i didnt mentioned that before clearly).
I also checked continuity of traces around resistors since i didnt had any boardview and wanted to guess which resistor is which. Later i bought the boardview and turned out my checks were correct and none of the traces seem to be broken.

Is it possible that resistors can give proper resistance measurements, but under load in circuit they behave like broken?

matic napisał(a):You can replace this transistor for example with 2N7002KDW or L2N7002DW, which is usually easier to find on some scrap board.

Thank you for info. I'll try to find and replace just in case.

AveoCross napisał(a):i didnt had any boardview and wanted to guess which resistor is which.

AveoCross napisał(a):Is it possible that resistors can give proper resistance measurements, but under load in circuit they behave like broken?

Possible, but very unlikely.

For the test you can also remove the resistor PR639 from the board and 12V should appear on pin 1 of chip PU602.

After a few days of intense use (constant Windows XP updates) transistor PQ600 let out a magic smoke. Its possible it was the culprit from the get go.
I just bypassed it by bridging its both drains together and laptop works again.

AveoCross napisał(a):I just bypassed it by bridging its both drains together and laptop works again.

I don not recommend that as it can lead to very undesirable consequences in case someone plugs the battery to the machine. The battery may fail or even explode in this case.

With this transistor bridged, there is also no more power supply reverse polarity protection and no over-current protection.

After "repair" from previous post i noticed that battery is not charged. I did some more measurements and noticed in schematic that by bypassing PQ600 i effectively removed Vmid voltage source that leads to pin 1 of Charger IC. I tried providing that voltage from A/D_DOCK_IN, battery started charging but weird stuff was happening - laptop was indicading charging even after unplugging power supply.
I ordered all proper parts - PQ600 and PQ603 and PQ601 that i end up frying while testing.
Replaced PQ600 with AO4805
Replaced PQ601 with AM4825P
Replaced PQ603 with 2N7002KDW
Laptop was behaving the same as without any repairs - worked from battery, no charging, not working from charger. Remeasured PR636, PR637, PR638, PR639, PR623 (all off the board), removed PC624, PU602. Checked traces. Everything was good. No shorts to ground, proper continuity, proper resistances. Still no 6V on pin 1 of PU602, even without PR639 on board.
Measured pin 3 of PQ603 to GND and seemed suspiciously low - 1MOhm. Took another 2N7002KDW and tested its pins - open line. Replaced, laptop started working from charger and charged battery. Though when i measure pin 1 of PQ603, voltage drops to around 4V slowly, starting from around 5.6V when my meter begins to show something. I hope thats fine and impedance of my meter just causes voltage to drop. Laptop still works ok from charger though.

One thing is a bit off yet - while battery is plugged in and I connect charger, board buzzes and PQ600 heats up a lot very fast. Pins 6 and 5 shows voltage jumping from around 8 to 10V.
When i connect PSU without battery and then connect battery, its works just fine.
Sometimes it also light off charging LED after i power up the laptop.
I lost a PC615 while measuring and soldering previously and currently have nothing to place there. I ordered a kit of various capacitors so i can put proper one there and hipefully it will fix that.

Any suggestions what i can yet check would be appreciated.

Measure the following voltages to ground with the power supply connected only (without battery):
- On pins 1, 4, 5, 8 of transistor PQ600.
- On pins 1, 4, 8 of transistor PQ601.
- On pins 1, 2, 5, 6 of transistor PQ603.

No battery, laptop turned off, measured to ground.

PQ600:
Pin 1 - 12.3V
Pin 4 - 2.2V
Pin 5 - 12.3V
Pin 8 - 12.3V

PQ601:
Pin 1 - 12.3V
Pin 4 - 9V
Pin 8 - 2.1V

PQ603:
Pin 1 - 0V
Pin 2 - 5.9V
Pin 5 - start at 5V, quickly drops and settles to stable 4V while measuring
Pin 6 - 0V

Remove the transistor PQ601 from the board and check, if the transistor PQ600 still heats up with the battery + power supply connected.