Vostro 3510 LA-L246p missing 3.3V and 5V

[trepachka]

This laptop (LA-L246p) came in with liquid damage in multiple spots. I had the board thorously cleaned. I found a shorted cap and a blown fuse in one location and now the laptop is charging. However, I am not getting 5V and 3.3V rails.

This board is almost identical to LA-L243p or LA-L241p.

PU501 (SY8288CRAC 5V converter) is getting ENLDO_3V5V (around 4.5V) on pin 11 but EN_5V (0V) on pin 12.

Similarly,

PU301 (SY8386BRHC 3.3V converter) is getting ENLDO_3V5V (around 4.5V) on pin 8 but EN_3V (0V) on pin 9

So, obviosly the enable signal is not turning these chips on.

I've read that SIO (MEC1515) generates these enable signals. Where do I locate EN_5V and EN_3V? On the SIO?

Thanks.

[trepachka]

Re: Vostro 3510 LA-L246p missing 3.3V and 5V

On a whim, I replaced PU501 chip and now I have 5V, 3.3V and 1.8V rails.

When power is applied, the PCH warms up a little under the thermal camera. SIO chip also gets power but computer is still refusing to start.

[ResoluteHawk]

Re: Vostro 3510 LA-L246p missing 3.3V and 5V

Do you get a charging light?

Disconnect all power. Check the resistance to ground on the 3.3V coil, the 5v coil, 1.8v coil, and Pin #8 of the BIOS chip.

Also, check resistance to ground at the input current sense resistor.

[trepachka]

Re: Vostro 3510 LA-L246p missing 3.3V and 5V

No charging light. I get 11.7V on battery leads when charger is plugged.

Resistance to ground, in Ohms:

5V coil: 2K
3.3V coil: 15.88K
1.8V coil: 2.78K

Without having the boardview, only the schematics, I do not know how to locate input current sensor.

[trepachka]

Re: Vostro 3510 LA-L246p missing 3.3V and 5V

Progress.

Replaced PUG1 chip due to one of its pins not getting 3.3V when I knew it was there. This is the same chip I found a shorted cap and a blown fuse nearby. Now, I am getting charging light and both coils are measuring 1.8V.

However, when pressing power button, the caps lock flashes once followed by another flash about 5 seconds later and that's it.

At the time when caps lock flashes, I get 1.2V RAM rail and the CPU heats up only for an instant.

So, the question is: am I dealing with corrupted bios, EC or are there additional components that need to be checked?

[trepachka]

Re: Vostro 3510 LA-L246p missing 3.3V and 5V

The charging light goes solid when power is applied whether the battery is attached or not. That's not a normal behavior. I reflashed the BIOS using BIN files provided in another thread. Now, the charging light goes on, then off, then solid again which is what I was expecting. However, when power button is pressed, I get no activity on the caps lock and only the PCH gets warm, CPU remains cold.

At this point I created a new thread seeking rebuilt bios. After that, I will most likely replace the SIO chip from a donor board (Inspiron 3511 LA-L243p).