Toshiba Satellite L355D will not power up from AC

[Herbssat]

Hello. I have a L355D that will only run from a charged battery and not power on from the ac adapter. The adapter and dc jack has been checked and is putting out the right voltage to the motherboard. Suspecting a problem with the battery management ic (U502); I checked voltages on pin 12(VCC-19 volts)PIN11(VREF-5volts) and pin 5(ACDET-1.35 volts). Everything looked to be in order there unless I am missing something. There is one suspicious circuit that I am looking at that could pose a problem. The main power diode D500 that is connected to mosfet Q504 outputs voltage in both directions with 18.7 volts at the gate. There is another mosfet (Q500 that is also connected to this mosfet that has the same voltage at the gate and source, but no voltage on the drain. This mosfet connects directly to the battery charging terminals. In fact, the mosfet reads open from source to drain. Maybe this is somehow reading the circuit as most mosfets fail from source to drain. Your help is greatly appreciated in solving this problem. By the way; this forum is great.

[b700029]

Re: Toshiba Satellite L355D will not power up from AC

Does it lock up when plugged in?

Yes - may be a problem with CPU vcore filtering capacitor, see that thread for more info.

No - Does it charge the battery?

Posting a schematic of the power section would also help.

[Herbssat]

Re: Toshiba Satellite L355D will not power up from AC

Thanks for the quick response. I will try to get a picture of the power section uploaded when I can. At the moment I have the board stripped down and the battery inserted. The green light and the orange light are illuminated so I presume that the battery is charging and it is recognizing the wall adapter. Even before I did all this; I checked the standby voltage at the power switch and it was 3.3 volts exactly. The unit still would not turn on.

[Herbssat]

Re: Toshiba Satellite L355D will not power up from AC

Thought I would just make an update on this. With the battery connected to the charging terminals the front panel ac indicator comes on as well as the battery charging light. There is a slight buzz and hiss as the battery charges but it does not look to be charging after about 3 hours. The indicator is still orange. Pressing the power button turns on the unit with the power on light, ac indicator and battery light lit. Once the battery is removed, all lights go out with the exception of a faint battery indicator light that blinks.The system again will not power up.

[Herbssat]

Re: Toshiba Satellite L355D will not power up from AC

I guess I will answer my own post. Q504 which is a front end 30volt power mosfet was shorted and slightly damaged. The giveaway was unstable voltage at the drain. In circuit, the mosfet read both ways with lower resistance. Decided to take it out of circuit and test it. The reading stayed the same. Ordered Vishay P channel mosfet from Mouser and problem solved. Thanks for the help.

[farrowz]

Re: Toshiba Satellite L355D will not power up from AC

Hi Guys,

I have discovered that Q504 popped (burned) and I am unable to read the part. Can someone tell me what this part is so that I can replace it.

Thanks.

[mikoz]

Re: Toshiba Satellite L355D will not power up from AC

Gday, I have a L500 01e that is having exactly this same issue. Will only run from a charged battery, charging light comes on when switched off but not charging the battery. Charging light will go out when power button is pressed. Does anyone have a schematic for this model by any chance? I am suspecting Q504 but require some specs to order a part from rsonline. Does this Vishay one look to be compatible (SI4953ADY-T1-E3)

Cheers.

[mikoz]

Re: Toshiba Satellite L355D will not power up from AC

I have found that Q504 is an Analogue Power AM4825P P-Channel 30-V (D-S) MOSFET with Gate Source Voltage +/_ 25v. I cannot seem to source this part anywhere but from eBay (china up to 8 weeks)? There is no Vishay product with more than +/_ 20v? Would this be a concern? What are the most important factors of for mosfet substitution?

Any clarification would be very appreciated.

Cheers.

[rievax_60]

Re: Toshiba Satellite L355D will not power up from AC

If the MOSFET is functioning as the adapter switch, its possible that the full 19v gets applied to Gate/Source. A MOSFET with a 20v gate rating will not have enough safety margin.

[guruji]

Re: Toshiba Satellite L355D will not power up from AC

Hi,
U can replace the mosfet anyone with p-ch with 10-11amps so si4825,or ao 4407, 4411,4413 all will work perfect as long u put a little high amps it will work i dont recommend si4435 as it is for a little older laptops will work but may blow off after a week or so.look is some old scrap boards there are plenty.in short they have to be 30volts rated and the amps is very important i generally use ao4407 it is a direct replacement for am4825.
Cheers.......let me know

[Bl4ckw1d0w]

Re: Toshiba Satellite L355D will not power up from AC

I had all the symptoms described and had been searching forever for a solution. I tried pulling everything out one by one to see if any external parts were the issue, then it came down to the motherboard. I was so frustrated, I wanted to throw it all out the window. Then I remembered an old trick of baking graphics cards in an oven to re flow loose not very concrete solder joints. Granted I wasn't about to stick a motherboard in my oven. So Picked up a heat-gun off eBay with an adjustable temp and wide nozzle set it at 480 and low enough pressure not move anything out of place and evenly heat up the board on one side. Left the processor in socket and the heat sink still on. You want to be careful not to bump it or even move the board a little bit because parts are so small they can easily be displaced. After a good 15 mins I could see the solder liquefy a tad and let the board cool off for a good 4 hours at-least to be safe. Flipped the board over and did the same thing on the other side after it was cool. To my amazement the laptop fired right up after I left it overnight too cool. The screen on an everything like the day I bought it. I hope this helps someone.

[blade009]

Re: Toshiba Satellite L355D will not power up from AC

i have an acer v5-432 series and whenever i plug in the adapter to motherboard it short out. anyone can assist me in how to get the problem address please as soon as possible, whatsapp +18764380954 email: denoham@yahoo.com