Toshiba Satellite P855 charger disabled after a while

[zioricci]

Hi everyone,

after a little operating time of my Toshiba laptop, ranging from about 20 to 45 minutes, the Power light goes off, the power supply switches from the charger to the battery and in fact the voltage of both gates of the 2 initial mosfets are at 0V so the 19V does not reach the PL201 inductor and the power comes only from the battery.

However, when i close the cover to turn off the laptop, the charger starts working again, charges the battery and the Power light turns on in amber color but after about 20 minutes the charger is disabled and the power light off, in short, everything as before.

Could it be the faulty BQ24725RGRR ?

The charger voltages I measured when the adapter is disabled are as follows:


1 ACN about 12.40 V
2 ACP about 12.42 V
4 ACDRV 0V
16 REGN 6.08 V
20 VCC 19.74 V
5 ACOK 3.4 V


on the other pins the values are

3 = 0.08 V
6 = 2.69 V
7 = 0 V
8 = 3.39 V
9 = 3.38 V
10 = 0.67 V
11 = 18.52 V
12 = 12.41 V
13 = 12.41 V
14 = 0 V
15 = 0 V
17 = 12.14 V
18 = 12.41 V
19 = 12.41 V

I also thought of an overheating for which the BQ24725 charger sends 0V to the gates of the 2 initial mosfets disabling the adapter but if i remove the adapter plug and insert it quickly, then the adapter resumes giving power to the laptop but after about 20 minutes (not immediately) it turns off and switches to the battery. Same story with another adapter.

Schematic: https://www.badcaps.net/forum/showth...914#post558914

[mon2]

Re: Charger disabled after a while

ACOK remains high after the power adapter is disabled so this means the charger IC is detecting the adapter OK.

ACDRV however is not ok since it should be ~25v to keep the 2 x DCin mosfets ON.

Often, as per @Piernov's sticky (buns) above, the 2nd mosfet is leaky.

Remove the ~4k resistor on ACDRV and confirm if the ACDRV outputs ~25 volts which is based on power_adapter_rail + REGN voltage = 19v + 6v = 25v.

[zioricci]

Re: Charger disabled after a while

Thx. I removed the resistor but the result does not change and on pin 4 ACDRV I always get around 0V.
Edit. I get 25V only when the adapter is active

I tried again but the 25 V are gone even with the active adapter.

[Vesko356]

Re: Charger disabled after a while

Thx. I removed the resistor but the result does not change and on pin 4 ACDRV I always get around 0V.
Edit. I get 25V only when the adapter is active

What do you mean by "active" - when the adapter is plugged into the laptop, or when the battery is charging?
Measure the resistance across the current sensor - the one after the first two fets (remove the charger and battery when measuring). Also check if it's heat up (and check mosfets also) during the charging.

.

[mon2]

Re: Charger disabled after a while

When the adapter is powering the logic board, then ACDRV must be ~25v to enable the 2*N-channel mosfets. If the gate voltage of these mosfets are not this boosted voltage (ie. equal or lower than the adapter voltage) then these mosfets should remain off.

Leave the ACDRV resistor off.

Connect the power adapter. Then carefully measure the voltage to ground of each mosfet.

Interested to review the source / gate / drain pin of each of the DCin mosfets. Post your measurements.

The ACDRV pin, without the series 4k resistor should be at ~25v. Otherwise the charger IC could be faulty.

[zioricci]

Re: Charger disabled after a while

What do you mean by "active" - when the adapter is plugged into the laptop, or when the battery is charging?

when the battery is charging and I notice it from the amber power light. Anyway, i put the resistor back on pin 4 and cleaned a bit and now on ACDRV the 25V is back but with the adapter charging. I waited for the charging indicator to go out and the voltage on the ACDRV is now 3.19V

Measure the resistance across the current sensor - the one after the first two fets (remove the charger and battery when measuring). Also check if it's heat up (and check mosfets also) during the charging.

Resistance is approximately 0.02 ohm and does not heat up when charging.

Thank you all for the help, but now I'm going to sleep, very tiring day.

[zioricci]

Re: Charger disabled after a while

When the adapter is powering the logic board, then ACDRV must be ~25v to enable the 2*N-channel mosfets. If the gate voltage of these mosfets are not this boosted voltage (ie. equal or lower than the adapter voltage) then these mosfets should remain off.

Leave the ACDRV resistor off.

Connect the power adapter. Then carefully measure the voltage to ground of each mosfet.

Interested to review the source / gate / drain pin of each of the DCin mosfets. Post your measurements.

I removed the resistor again

First mosfet
drain 20.03 V
gate 0 V
Source 3.3 V

Second mosfet
drain 12 V
gate 2.94 V
source 3.3 V

The ACDRV pin without the series 4k resistor should be at ~25v. Otherwise the charger IC could be faulty.

no it's 3.34 V

[Vesko356]

Re: Charger disabled after a while

when the battery is charging and I notice it from the amber power light. Anyway, i put the resistor back on pin 4 and cleaned a bit and now on ACDRV the 25V is back but with the adapter charging. I waited for the charging indicator to go out and the voltage on the ACDRV is now 3.19V



Resistance is approximately 0.02 ohm and does not heat up when charging.

Thank you all for the help, but now I'm going to sleep, very tiring day.

In my opinion, the BQ chip is most likely defective in this case, and it is best to be replaced.

.

[zioricci]

Re: Charger disabled after a while

Tomorrow i'll try to replace it with the one from the Toshiba P850 motherboard that I have as a spare. Mine is the P855 but they are the same. Let's hope that at least that works. thx.

[mcplslg123]

Re: Charger disabled after a while

Before replacing the charging IC, resistance between pin1-4/Pin1-8/Pin4-5 should be measured. Same should be measured for the discharging FET also.

[zioricci]

Re: Charger disabled after a while

Before replacing the charging IC, resistance between pin1-4/Pin1-8/Pin4-5 should be measured. Same should be measured for the discharging FET also.

I used an analog multimeter because with digital the measurements are not stable

R1-4 200k approx
R1-8 11k approx
R4-5 0 ohms

I didn't understand what to do with the discharge FET

[mon2]

Re: Charger disabled after a while

If you are measuring 0 ohms between pins 4&5 of the charger IC then this implies you have a short between these pins.

Post a clear pic of this area.

Was a service attempt made on this logic board? Was this ic replaced already?

[zioricci]

Re: Charger disabled after a while

If you are measuring 0 ohms between pins 4&5 of the charger IC then this implies you have a short between these pins.

Post a clear pic of this area.

Was a service attempt made on this logic board? Was this ic replaced already?

I had measured it with the analog multimeter, now with the digital one I measure 182 ohm.

Never service, never ic replaced
In the photo, the resistance that I put back looks bad but it's ok

[mon2]

Re: Charger disabled after a while

The resistance between pins 4&5 should not be so low. If this logic board has not been worked on before then to me, this charger IC is defective and should be replaced.

Otherwise consider to apply flux onto the perimeter of this IC and reflow it with low air pressure. The solder will turn to liquid and naturally allow for the ic to return to their solder pads. This is to clean up any possible residue between pins 4 and 5.

[zioricci]

Re: Charger disabled after a while

You are basically telling me to reflow, ok done but nothing has changed.

It seems to have reverted to its initial state when I started the thread

https://www.badcaps.net/forum/showthread.php?t=117493

the battery is charged by the adapter but this no longer performs the function of powering the laptop, in fact if i remove the battery the laptop turns off.

[mon2]

Re: Charger disabled after a while

Do you have a schematic of this laptop? If yes, link it here but do not post the schematic here. Post it in the schematic section only.

Based on the conditions, without a load on ACDRV pin, the voltage on this pin should be ~25 volts to enable the DCin mosfets. So without the 4k resistor, ACDRV should be 25v.

The gates of the DCin mosfets are commonly shared. Yet, you have 2 different measurements in an earlier post. Remove all power. Meter in resistance mode.

Check the resistance from gate pin #4 of the first mosfet to pin #4 gate pin of the 2nd mosfet. What is the resistance?

That is, the gate voltage should remain the same of each of the DCin mosfets unless this design is unique.

Next issue is the low resistance between pins 4&5 on the charger IC. Be sure there is no power and battery to the logic board when checking resistance.

Remove all power. Meter in resistance mode.

Check the resistance across the mosfet pins:

Source & drain
Source & gate
Gate & drain

Post each measurement. Repeat for each of the DCin mosfets.

[zioricci]

Re: Charger disabled after a while

Between the 2 gates the resistance is zero, in fact they are connected together and driven by ACDRV.

Without 4k resistor ACDRV is not 25 but 3V.

For both mosfets:

sources & drains Infinite
Source & gate 8k
gates & drains Infinite

Where is the schematic section ?

[Vesko356]

Re: Charger disabled after a while

Where is the schematic section ?

https://www.badcaps.net/forum/forumdisplay.php?f=41

Edit: Link to the schematic (La-8391p) added at post #1

.

[mon2]

Re: Toshiba Satellite R855 charger disabled after a while

With a 8k resistance, source & gate means that you have at least one defective mosfet.

Remove the 2nd mosfet and check the resistance again.

PS: Textbook case from the sticky above by @Piernov.

[zioricci]

Re: Toshiba Satellite R855 charger disabled after a while

I don't understand what happened before but it has always been open circuit and in fact now it is not 8k but open.

Also, between drain and source depending on how i put the multimeter leads, i get open or the threshold of the two diodes.

The two mosfets seem ok.