Lenovo IdeaPad Gaming 3 15ACH6 - no power

[gleniu]

Hi, I have a problem with a Lenovo IdeaPad Gaming 3 15ACH6 laptop. My nephew asked me to replace the charging port because the laptop wasn't charging. This issue had happened in the past, so I knew that replacing the port was only a matter of time. Until now, my nephew managed to deal with the problem using a temporary solution: bending the positive metal tabs inside the port with a thin tool. However, this had stopped helping for a while. Today, I replaced the port – and to my surprise, after the replacement, nothing happens when I plug in the charger: the power LED doesn't light up, the laptop won't turn on, and the battery doesn't charge.

I'm not sure if I could have damaged something during the replacement — I'm an amateur and do this as a hobby, so I can't rule that out. However, I followed all safety standards, and I've successfully done this before on other laptops. So I tend to think my nephew overdid it with bending the contacts and caused a short that damaged something on the motherboard, even before I replaced the port.

What's strange is that the charger protection doesn't kick in now — when I connect it to the laptop, it constantly outputs voltage, and there is voltage on the correct pins in the charging port. There is no short circuit at the charging port itself. I've noticed that when the charger is plugged in, some small components – and due to my limited electronics knowledge I’m not sure what they are... capacitors? resistors? – get very hot (I’m attaching a photo pointing out these components).

Schematics for my motherboard are here: https://www.badcaps.net/forum/troubl...64#post1725864

I’d really appreciate your help as you would for a complete beginner – in the past, you helped me diagnose an Acer laptop on this forum, despite my lack of expertise. What should I check and how at the very beginning?

[reformatt]

This is a pretty standard fault with Lenovo's with that kind of DC Jack. The plastic in the centre pins collapse allowing 19V to contact the ADP_ID pins, and unfortunately Lenovo send this line directly to the EC.

Only solution is to replace the EC (in this case a KB9022QD) and it also needs reprogramming. You can either source one pre-programmed or you will need a tool like a SVOD4.

[gleniu]

Thank you very much for your response. I just want to clarify a few points (this really shows my lack of experience and theoretical knowledge). Before installing the new socket, I plugged the charger into it and checked the voltages on the individual pins, but it did not occur to me to check where these voltages should actually appear – I simply did not assume the new port was faulty. According to the boardview, the power jack has the following pins:
1 - GND
2 - APDIN
3 - N21106349
4 - APDIN
5 - GND
6 - GND
7 - GND
In my measurements, there was 19V on the APDIN pins (2 and 4) but not on pin 3. If I understand you correctly, voltage should not appear there at all (especially without soldering the port), and this means that the port was damaged from the start (before I installed it), and I probably fried the EC by soldering it into the board and pluging in the power – is that correct? Does it make sense to try replacing the port again with a working one without replacing the EC – in other words, is it possible that the EC survived those 19V?

[reformatt]

IIRC, Lenovo's use a simple voltage divider on the ADP_ID line to identify what wattage adaptor is connected. One half of the voltage divider is in the laptop (in this case a 750 ohm pull up resistor to +3VL) and the other half is within the power adaptor. This line however goes directly to the EC with no isolation or overvoltage protection. As a sidenote, Dell use a different method for their adaptor identification, but there is plenty of protection circuitry to prevent damage to the EC should 19V enter this line. Lenovo simply don't give a shit because this design is replicated across many of their laptops.

If you get 19V down the ADP_ID line (which you do as the 19V and ADP_ID pins short together when the centre plastic breaks), it will damage the EC as this shouldn't exceed 3V. The last time I had this with a collapsed DC jack, the laptop would partially work but wouldn't POST. In the off state without battery connected, the laptop was consuming 100ma or so, and thermal camera showed this was being consumed by the EC. Replacing the EC and reprogramming fixed the fault. The EC hadn't completely failed either, I could still dump it's firmware before replacing it.