Toshiba P855 only works with battery

[zioricci]

Re: Toshiba P855 only works with battery

Is the other motherboard a working board? If yes, it will help to troubleshoot this unit.

Same adapter works with the other motherboard?

You can measure the voltage to ground of each pin on the charger IC under the same conditions -> add the adapter & battery. Post the list.

Then let us compare the values from the known good motherboard against this one.

You mentioned earlier that you were attempting to remove a mosfet. Was it on this board?

Which one?

The other motherboard of the P850, has 2 problems

With the adapter and the battery together, there is an exaggerated absorption certainly due to a short, while either the adapter alone or the battery alone does not cause the short but I have a black screen.

[mon2]

Re: Toshiba P855 only works with battery

So there is a leaky mosfet also on that board.

Continue to remove the gate resistor on the first board.

[zioricci]

Re: Toshiba P855 only works with battery

Unbelievable, I tried taking out a stick of ram and it booted up to windows

[zioricci]

Re: Toshiba P855 only works with battery

More specifically, I have 2 sticks of Ram one of 4MB, present since the beginning of a laptop bought new, and the other of 8MB bought online recently because I suspected the Ram but I hadn't flashed the bios yet.

After the flashing it started only with the battery and just now, by chance, I wanted to try only with 4MB of ram but I moved it by slot, then I added the 8MB one in the slot where there was the 4MB one, then in reversed positions and the laptop booted up.

I try to reverse the positions, as they were before, and in fact it does not start and remains stuck on the logo.

Question: but when the sticks are different, for example 4MB and 8MB, is it possible that the 8MB one has to fit in a specific slot to start the machine ? It's strange because the bios sees 12MB exactly equal to the total ram installed.

[mon2]

Re: Toshiba P855 only works with battery

Interesting observation. You will have to review the Toshiba laptop memory guide for this model to understand which permutations are permitted.

I recall a similar bad experience from a motherboard vendor who offered a table of all permitted ram stick combinations. We wanted to expand to 32GB yet none of their approved vendor list sticks worked. Killed a day of trial and error and truly believe the fault was with their BIOS coding. Purchased a different brand (ASROCK I believe) which on the other hand, could not fail to recognize the many different sticks of ram we purchased -> each set allowed for a working 32GB configuration. The ASROCK bios actually came back with guidance that we could clock the sticks even faster than the defaults while the first motherboard would just not power up unless we went for a lower amount of ram.

[zioricci]

Re: Toshiba P855 only works with battery

Today i realized that laptop battery not charging , i checked the voltages on the 9 pins of the battery which starting from the ninth pin are

12
12
x no connected
0
2
3.3
3.3
0
0

and also the three mosfets PQ201, PQ202 and PQ205 which are good

[zioricci]

Re: Toshiba P855 only works with battery

I also measured the voltages on the charger IC, with battery and adapter together, these are

1 20.06
2 20.04
3 20.01
4 25.81
5 3.4
6 2.69
7 0
8 3.4
9 3.4
10 0.67
11 12.59
12 12.60
13 12.60
14 0.69
15 0
16 6.07
17 18.77
18 13.90
19 12.58
20 19.63

[mon2]

Re: Toshiba P855 only works with battery

Can you double check your measurements for pins #1, 2 and 3? The values are not logical as posted.

[zioricci]

Re: Toshiba P855 only works with battery

Even now I read those values. Doesn't it seem logical to you that they are all the same at 20V? The measurements are as in the first check on page 1, done with the adapter only connected.

I add more clues.

Assuming that the indicators are on, the 2 initial mosfets give regular values, but after a while it happens that the adapter is disconnected, its indicator goes off, the second mosfet from 0V and only the battery remains which obviously gets discharged without the adapter .

[zioricci]

Re: Toshiba P855 only works with battery

I was wrong, the battery is charging, it is Windows that considers it discharged, it tells me 8% autonomy but it has a voltage of 12.52 V and after a few charging cycles, the Windows indicator stops but it continues to charge.

Any suggestions to fix ?

[mon2]

Re: Toshiba P855 only works with battery

Remove pq206 off the logic board. Power up again.

Measure the voltage to ground of pins #1, 2 and 3 on the charger IC.

The above readings are not making sense to me as when the adapter is mated with the board, pin #3 voltage comes first and should be a higher voltage than pin #2 and pin #2 should be higher than the voltage on pin #1.

Post the measurements.

[zioricci]

Re: Toshiba P855 only works with battery

I thought it was the gate i.e. pin 4 that had a higher value, in fact it is, about 25 V.

Another clue.

Tonight before going to sleep the battery was 100% charged (12.52V), I switched it off and this morning it was at 12.25V, with the charger LED off.

Why does it turn off? I imagine that at the output of the first two Mosfets there are 0 V.

[mon2]

Re: Toshiba P855 only works with battery

Did you review post #51?

[zioricci]

Re: Toshiba P855 only works with battery

Did you review post #51?

Yes of course I read, I forgot to say that I tried to remove PQ206 but I can't eradicate it, even by increasing the hot air, nothing won't come off.

With the multimeter, however, it seems to work.

[zioricci]

Re: Toshiba P855 only works with battery

Remove pq206 off the logic board. Power up again.

Measure the voltage to ground of pins #1, 2 and 3 on the charger IC.

The above readings are not making sense to me as when the adapter is mated with the board, pin #3 voltage comes first and should be a higher voltage than pin #2 and pin #2 should be higher than the voltage on pin #1.

Sorry I got confused, in fact the voltage of pin 3 exceeds that of pin 2, even if by only 0.01 V. Do you think this is caused by PQ206 and above all, it could be the reason why Windows sees low battery even when not it is ?

I might not worry if Windows didn't take the initiative to shut down my computer suddenly when it deems that the battery drops below the critical level, even when charged, but I haven't done this test yet.

[zioricci]

Re: Toshiba P855 only works with battery

A curiosity about the battery charging process, is it normal that during charging, the current supplied by the adapter decreases over time ?

[mon2]

Re: Toshiba P855 only works with battery

Measure the voltage to ground of each pin on pq206.

Post each measurement.

The pq206 device is a sot-23 package and should be simple to remove with enough hot air temperature and with the use of flux. Spin the hot air in tight circles over the part. Keep any such heat away from the sensitive lcd display, keyboard, etc parts. Practice on a donor board if available.

For now, just measure the voltage to ground of pq206.

Also consider to check the resistance again of the 2 * DCin mosfets. Remove all power. Meter in resistance mode.

Measure the resistance checks like before.

Source & drain
Source & gate
Gate & drain

Yes, it is normal for the current charge profile to decrease as the battery charges to full capacity.

[zioricci]

Re: Toshiba P855 only works with battery

Measure the voltage to ground of each pin on pq206.

Post each measurement.

Drain 25 V
Source 19.35 V
Gate 4.7 V

Also consider to check the resistance again of the 2 * DCin mosfets. Remove all power. Meter in resistance mode.

Measure the resistance checks like before.

Source & drain
Source & gate
Gate & drain

-----------------> 1 mosfet - 2 mosfet

Source & drain---> 4Mohm - Infinite
Source & gate---> Infinite - Infinite
Gate & drain ---> 36 Mohm - Infinite

Yes, it is normal for the current charge profile to decrease as the battery charges to full capacity.

thx

[mon2]

Re: Toshiba P855 only works with battery

Remove all power. Meter in resistance mode.

Measure the resistance of pr210 resistor. Is it a stable reading of ~10 ohms?

Next, meter in diode mode.

Red meter probe to vin pin #3 of diode at pd201. Black meter probe at pin #1 of pd201.

What is the reading? Then swap the probes. Post this measurement.

Repeat with testing the 2nd diode at pd201 using the same process.

In reviewing this thread, the voltage drop from Vin to the VCC pin is too high for some of the measurements.

[zioricci]

Re: Toshiba P855 only works with battery

The two diodes look good, the measurements are:

in reverse bias (red on cathode and black on anode) the first diode does not conduct and in forward bias I have the junction of 0.335 V. Same measurements for the second diode of PD201.

Yes, PR201 is 10.1 Ohm stable.