Latitude 7330 motherboard photo near the bios chip

[trepachka]

Hi, while desoldering the bios chip, I accidently knocked off 2 components: a resistor and a capacitor. I am trying to figure out their position. I didn't take the picture prior to this, my bad.

Could someone, please post a close-up photo of the bios chip, in particular the area where "DC1" and "UC2" are printed on it? There is a capacitor and a resistor there I am trying to find their original position on the motherboard.

Thanks.

[djtaotao]

I'm working now on my 7430 - LA-L581P, can you please check if it is the same MB, maybe I can help you?

[trepachka]

Yes, it is the same motherboard. If you could take a close-up photo of the area, in particular the side where "DC1" and "UC2" are printed next to the bios chip, that would help me a lot.

[djtaotao]

I hope this helps.

[trepachka]

Thank you. Can you post a close-up bird's view of the first photo? Namely, positioning of the capacitor and the resistor just below the bios chip

[djtaotao]

😁

[trepachka]

Hey, sorry. You have a close-up of the other bios chip. I am mostly interested in the area where "DC1" is printed. You can actually see the resistor and the capacitor over there. From the picture it's not clear which one is which. Also, that capacitor has "+" and "-". I need to know which way to solder it.

Could you, please take a more detail photo of just that area? Thank you kindly.

[djtaotao]

There are a resistor and a diode to the right of DC1.

[trepachka]

Yes, that's it. Thank you.

[djtaotao]

I'm happy if I helped you.
Now if you can help me I'll be even happier.
Can you please measure for me the voltage of main power rail on PC715, PJ100 or PJP202 with charger conected but with and then without battery connected?

[trepachka]

I should resume working on this laptop this weekend. Can you take photos of the location of each of these components and I would be happy to take measurements for you?

[djtaotao]

All those points should be the main power rail.

[trepachka]

Voltage measurements taken @ PC715:

8.5V => Charger is on, battery is off
16V => Charger is on, battery is on @ 15% charge. This voltage keeps rising a little as the battery is getting more charged.

If you need me to take other measurements, let me know since computer is currently sitting disassembled.

[djtaotao]

I have almost the same voltages except the fact that the battery is not charging, without battery I have +8.6V and with the battery on I have constant +17.2V. Of course the laptop is not powering on and this is my first laptop I'm trying to repair .
The charger is negotiating the voltage and the USB meter shows 19.98V and 0.08A so definitely is not charging. The led on the power button light up and stays on for 30s, turns off for 1s and turns on again for 30s and so on.
I have 3.3V and 5V present. I don't know who's the suspect.

Can you measure the following coils please?
PL201 to GND
PL501 to GND
PL602 to GND
PL603 to GND
PL604 to GND

[trepachka]

Ok, I will take the measurements later today.

[trepachka]

I get the following:

PL100 780 Ohms
PL201 45 Ohms
PL101 10.5K Ohms
PL604 125 Ohms

I think PL602 and PL603 are obscured by the heatsink and these two are on the side of the CPU. They measure 80 ohms which is what to be expected.

[djtaotao]

Thanks!
I got different measurements, maybe you have a different processor & ram. I have an i7 + 16 GB of ram.

PL602+PL603 = 12.2 ohms
PL201=32ohms
PL604=21.7ohms
PL501=163ohms

[trepachka]

Is your computer running on just battery? In case the battery is down to 0%, do you have a voltage injection tool to charge the battery a little bit? Because if the computer runs on battery, then the charging circuit is definitely the culprit.

I am concerned about PL602+PL603 resistance. 12.2 ohms is somewhat low. I am ok with 40+ ohms. This is just too low. But if computer runs on battery, then I take it back.

Check the battery charging chip pins. One of the pins, REGN I think, is supposed to show 6V. That's a good indicator the chip may be Ok.

[djtaotao]

The battery is charged, it has around 16.2V. I tried to inject some voltage on it but it takes no current.
The laptop has this behaviour, is not running and is not charging. I already changed the charging IC which is ISL9538 and the double mosfets PQ700 and PQ701. I don't know where to check the REGN signal on ISL9538.
The schematic is almost the same as the one attached.

[trepachka]

Since you have already changed the charging IC, I am just going to assume it's still good. Do you get any power rails, in particular 5V and 3.3V? Are they present?

PU102 is responsible for generating 5V power rail.
PU100 is responsible for generating 3.3V power rail.