Toshiba a665 mobo LA6062p rev.2 dead

[pcbmaniac]

Hi all.
I'm not a PRO to laptop mobo repairing but i can managed to fix some easy problems for a couple of friends.

Now i need advice about laptop mobo LA6062p rev. 2. Here is the problem.
Every cable, ribons etc. are unpluged. No battery connected, no cpu, no ram, no pcb bluetooth or wifi. Only mobo PCB.
I put 19V DC in to jack and made some measures. I get 19V in PQ7 but i get only 0,4V at P3 test point. Is that correct?
Please advise what more measurements i can get.
TIA
This is the schematic i will use.

[khaahk]

Re: Toshiba a665 mobo LA6062p rev.2 dead

Voltage on P2 and pin 4 of PQ7 ?

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

Voltage on P2 and pin 4 of PQ7 ?

Thank you for reply. After a couple of measurements, i found a bad mosfet PQ32 which i have already replaced. Now i 'm happy to tell that power led AC in is on and puting the battery i get battery charge led on also! Battery pins has 11,8V DC now.
Tommorow i will check if charging well.
Also i have 5V DC in 5,6,7,8 of Q30 and 3,3V DC in drain of Q29 as well.
What other measurement i can take to be ready for putting the CPU safely?
Have in mind that i have also a small POST tester with LCD display. How can i use that too? Thank you for your patience!

[khaahk]

Re: Toshiba a665 mobo LA6062p rev.2 dead

What was PQ32 problem? If shorted, then you probably have something dead on 1.05V rail (GPU most likely). You can measure the resistance of rail, if gpu then it should be 6-12 ohms or something similar.
Only real measurement you can make is to check the high side cpu mosfets for short, anything else will be seen when powered on.
For using POST tester you have to solder it to LPC debug port, this mainboard does not have routing of LPC to miniPCIe port. Check your post tester for LPC pinout.

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

I have a semi professional PSU. Can i put 1.1V at 3A between ground and to all inductors to check for bad caps? Also i noticed that my POST tester has LPC possibilities. How can i measure with this?

[khaahk]

Re: Toshiba a665 mobo LA6062p rev.2 dead

You can use PSU or measure resistance on inductors, but most controllers have protection against overcurrent. The danger is if upper side mosfets have short circuited, then the adapter voltage could go directly to low voltage rails. Find LPC header on the schematics and solder wires (AD0-AD3 and 3.3v, reset, frame, gnd) from POST tester to the header on mainboard (the schematic indicates there should be pads near memory). I think you are rather safe to try to power on the mainboard. The POST card might of any use afterwards, when all the power lines are ok but the machine won't boot.

[popeye]

Re: Toshiba a665 mobo LA6062p rev.2 dead

If you put 1.1v at 3amps to that rail if anything isfaulty you will kill the mb straight away

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

At about 2 hours from now, i will go to my experiments lab where the PCB mobo is waiting and i will be on line to do every test step by step together. Thank you for your support.

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

I am ready to do some tests. Who can help first?

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

After a couple of measurements for low resistance to all the rails, i have decide to put cpu, ram and do a quick test. Guest what? It works! Thank you for your replies.

[luktech]

Re: Toshiba a665 mobo LA6062p rev.2 dead

Please how do you confirm that PQ32 was shorted

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

@luktech. I took out of pcb the mosfet and measured the PQ32 with osciloscope component tester and it looks straight vertical line. (0 ohms means bad mosfet). I also made the same measure to a good one and after comparison i changed it.

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

Update: Now laptop is switching off randomly. What should i check first?

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

Update: I noticed that the laptop shuts down from a thermal overheating. I put a direct airflow from a powerfull fan and the laptop works as long as the fan working. Is this a bad cap sign?

[pcbmaniac]

Re: Toshiba a665 mobo LA6062p rev.2 dead

Update: I will try to describe step by step my acts to this laptop.
Connecting DC 19V at power jack then Power AC LED is on. I press the power button and the system is trying to power up, the fan is runing only for 1-2 sec's.

Here are the steps:
1) I try to power up the pcb with only RAM and CPU but it can't power up. I put a little presure to some places on PCB and i try to discover where the shutdown happens but i don't have a clue yet.
2) I try to solder some electro caps in parallel with the originals 2,5V caps, but no clue yet either.
3) I solder a debug LPC card to appropriate possitions but also the same thing there too. I take only the 3,3V only after i press the power on button.
4) I took out the CPU and now i can power up the PCB for little seconds only (8-10 sec's). In this situation i take some voltage measurements in the coils which seems decent to me.
Not forgeting to mention that when i discharge all the electro caps once, the system power up with CPU and RAM but only for 6-8 sec's.

I need your help. Is it a good idea to change the 2.5V electo caps? (About 16 items) Do i need reflowing instead?
I do have a hot air station for my personal use and this laptop belongs to my nephew so it would be nice for him to fix it.
TIA