Toshiba l300 no power

[juus]

Re: Toshiba l300 no power

No one around to lend a hand?

[juus]

Re: Toshiba l300 no power

Seems like no can help, thanks anyway.

[gretti]

Re: Toshiba l300 no power

I have a L305D, same board I think? The system was working but when the ac adapter was plugged in, sometimes the system was switching from AC to Battery very rapidly. You could see this in windows. I used a universal AC adapter that had more amperage than the original and the system stopped switching and was running fine. The thing that I did notice was that there was a high pitch sequel coming from somewhere on the board, just around the battery terminals. Then sure enough the system died, no power. This sounds like the same problem that you are having with your L300. I will fix this one when I have time, but it looked like either a bad capacitor or a bad MOSFET. I will let you know what I find.

[juus]

Re: Toshiba l300 no power

keep me posted.
I will be replacing the mosfet today and see if anything changes.
All other components seem to be fine so thats all i can think of that could be problem.

[juus]

Re: Toshiba l300 no power

Or at least i mean changing U502.

[momaka]

Re: Toshiba l300 no power

Hi juus,
sorry for the delay, I got caught up with a bit of studies with my summer semester (we're almost done).
Anyways, I haven't forgotten about this thread. To answer things in order... all the measurements you posted on the previous page (post #20) seem to be in order.

I'm not sure if replacing U502 will help. These ICs don't usually burn out that easily. Reason I mentioned it is because its data sheet contains a sample circuit that may be similar to the one in your laptop. This, however, I can't verify without the board in front of me due to the circuit's complexity.

In any case, you can perform some voltage measurements on some of the pins to see what may be going on in the circuit.
For now, just check voltage on Pin 12 (VCC), Pin 5 (ACDET), and Pin 11 (VREF5). Use the data sheet I linked to on the prvious page as a reference. Let me know what voltages you get on these pins with the adapter plugged into the laptop. Battery may be left out for now.

About those pins above and why they are important:
VCC is the voltage supply pin for U502 - if you don't have voltage there, then the laptop won't power up.
VREF5 is U502's internal 5v voltage regulator so you should have 5v on this pin. Of course this will only happen if VCC is present and higher than 5v.
ACDET signals U502 when the AC adapter is plugged in. ACDET is derived from a resistor divider between the adapters (+) and ground (-).

[juus]

Re: Toshiba l300 no power

thanks, will check once at home and post results.
if its not that then im lost.

[juus]

Re: Toshiba l300 no power

Pin 12 VCC shows 0.5V
So it seems IC is blown?

Sorry took so long, work had me quite busy.

[juus]

Re: Toshiba l300 no power

U502 is the battery charge management if i understand datasheet correctly.
So why does it not power from only AC or are the 2 linked?

[grant1842]

Re: Toshiba l300 no power

Sounds like a power jack problem.
I repair laptops allot.
Please see my article here on EE on how to fix your powerjack.
http://www.experts-exchange.com/Hard...her-Board.html

[grant1842]

Re: Toshiba l300 no power

ANd the first thing I allways check is the power adapter for the right voltage.

http://www.experts-exchange.com/Hard...r-Voltage.html

[juus]

Re: Toshiba l300 no power

I have checked the power adapter & its fine.
Have replaced the powerjack as this is what initially broke off & i suspect shorted out and damaged something else on the main board.

Thanks for your input

[momaka]

Re: Toshiba l300 no power

Pin 12 VCC shows 0.5V
So it seems IC is blown?

Like I said, not necessarily. There's many other components that can be faulty and causing U502 not to have power.

U502 is the battery charge management if i understand datasheet correctly.
So why does it not power from only AC or are the 2 linked?

Yes, they are linked. If you look at the sample circuit on page 21 of the U502 data sheet, you will see that U502 is basically what switches power to the laptop between battery and AC adapter.
U502 is also connected to the system bus. Without U502, the laptop cannot turn on.

I think the next thing to check is to plug in the AC adapter (again battery removed) and see if any components get hot - you can use your finger for that (it's not scientific, but it's good enough). Particularly, check to see if U502 gets hot.

If you can't find anything, remove power and perform a diode test with your multimeter between pin 12 (VCC) of U502 and the positive input on the power adapter plug. For this test, have your black multimeter probe (-) on pin 12 (VCC) of U502, and the positive probe (+) at the power adapter plug. What numbers do you get?
Repeat the same test above, but this time measure resistance. Post what numbers you get.

Also measure resistance between pin 12 (VCC) of U502 and ground and post what resistance you get.

[fabiog]

Re: Toshiba l300 no power

MOMAKA my L300 doesnt switch on with charger plugged in only with battery could the U502 be to blame?
I also get a hissing/buzzing sound when i plug it in.

[momaka]

Re: Toshiba l300 no power

MOMAKA my L300 doesnt switch on with charger plugged in only with battery could the U502 be to blame?

No, not necessarily. Again, assuming it's bad without checking other components and voltages on the board is the wrong way to troubleshoot these issues. Repeat same procedures as juus - check voltage on VCC, ACDET, and VREF5 to see if your U502 is getting proper power.

[fabiog]

Re: Toshiba l300 no power

Strange thing is that it doesnt make the noise and starts fine when cpu is removed but that could just be that it's not powering up properly without CPu.

[artois7]

Re: Toshiba l300 no power

Strange thing is that it doesnt make the noise and starts fine when cpu is removed but that could just be that it's not powering up properly without CPu.

Then try another CPU.

[dycc]

Re: Toshiba l300 no power

you have to change the u502 integreted circuit . i get the same issue many time and it was always this chip the fault. (texas instrument BQ24721c)

[dycc]

Re: Toshiba l300 no power

do it and let me know the result

[kalu]

Re: Toshiba l300 no power

Hi.
I'm new here...
All toshibas L300 and A300 have this problem and similar ones... this problem is genereted by NEC TOKIN.
Some times the computer dont start becouse de VCORE controller is off, if you can't find it try to change the nec tokin OE907 to 4 capacitors of tantalo 330mf 2,5v...
If you want some help... ask please.