Repairing my Lenovo 3 14 Laptop: lights and fan but no video - Page 1
Forum section: electronics / repair

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 27, 2017, 11:42:05 pm
content: I'm really not sure where to start on this board. I measured most of the large ceramic capacitors, none were shorted, and the same with most of the obvious mosfets.When I power it on, the keyboard backlight cycles on and off, and the fans run. No beeps, no video. I've got TWO machines. My original core i5 model which worked but got killed by a charging incident, and my core i7 nvidia GPU model which I recieved dead (note I did not buy these machines working)The core i5 model is completely dead, I'm not going to try fixing it. It can be a donor board for parts though, but the core i7 nvidia model has more components due to a dedicated graphics chip.Where should I start? Perhaps measuring the CPU and GPU core voltages?It does beep without ram installed, so something's working

author: bd139
author_rank: Super Contributor
timestamp: November 28, 2017, 12:15:21 am
content: First thing first, get the model number and the service manual for it. Lenovo have pretty extensive service manuals with FRU checks and diagnostics online. Go through that and run the diagnostics first. This will narrow it down to an FRU. At that point, replace the FRU. It's not worth diagnosing it any further. You can probably get parts for not much cash on ebay.I've revived several dead Lenovo machines for very little investment.At a push, pull the entire FRU and inspect it for damage or try and power it up without i.e with screen cable, IO board detached. I had a dead X201 which had a short on the SD card/audio subassembly where someone had jammed some crap in the SD card slot. I just replaced this and the whole machine came up like new.

author: cdev
author_rank: Super Contributor
timestamp: November 28, 2017, 12:16:38 am
content: Does it even attempt to boot from a hard drive or CDROM? If so, are you able to plug in an external monitor and see anything?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 28, 2017, 12:22:39 am
content: Quote from: cdev on November 28, 2017, 12:16:38 amThe internal and external displays do nothing. Caps lock LED does not work. My SSD has an activity LED built in and it does nothing as well.Quote from: bd139 on November 28, 2017, 12:15:21 amI'm down to nothing but the DC jack, RAM and eDP cable connected to the mothetboard. I know for certain everything but the board is in working order.The motherboard for this machine is almost 300$ for the base model board and I'm troubleshooting the high end board, which actually isn't for sale anywhere. I'm going to have to do component level repair. I've been 2 for 2 with dell motherboards, they were both easy to find what went wrong though, just follow the sooty skidmark. Sadly nothing has expired violently on this board.

author: bd139
author_rank: Super Contributor
timestamp: November 28, 2017, 12:28:21 am
content: I wouldn't do board level on these myself. I wish you luck however. If you do succeed or even try, much respect

author: imidis
author_rank: Frequent Contributor
timestamp: November 28, 2017, 12:39:50 am
content: It's a little tought wihout a schematic to know which voltages should be present where, not sure if ones available for it.But before you do that I would remove the hdd, cd drive if it has one wireless card and see what happends when you try and boot it.Of course, if there is any spills thats a good spot to check out as well.If it's a removable processor carefully try reseating itram beep codes good sign.. It's something

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 28, 2017, 12:55:48 am
content: Quote from: imidis on November 28, 2017, 12:39:50 amSsd and wifi card has been unplugged. Same for the keyboard, trackpad, etcAll I've got is power and the LCD display connected.CPU and GPU are both soldered to the board.Ram stick passes memtest on my gaming laptop so I know the ram stick is good.Sadly no liquid damage at all. Board is in good shape.

author: imidis
author_rank: Frequent Contributor
timestamp: November 28, 2017, 12:24:03 pm
content: If you are getting bios beeps the cpu is likely ok and functional so I wouldn't invest time in that. The fan keeps running right?I would probably focus to start on the supplies to the ram and video if you can track them down.

author: grifftech
author_rank: Frequent Contributor
timestamp: November 28, 2017, 08:05:23 pm
content: have you tried an external display

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 28, 2017, 08:39:50 pm
content: Quote from: imidis on November 28, 2017, 12:24:03 pmYeah GPU core is probably my next bet.The fans come on when first woken, and then they turn off. As the idle CPU warms up, the fans begin to go again. The keyboard backlight cycles on and off so it seems like its continually trying to POSTQuote from: grifftech on November 28, 2017, 08:05:23 pmYeah, no luck. I've also tried a known working internal display (the other machine's chassis)

author: Old Don
author_rank: Regular Contributor
timestamp: November 29, 2017, 12:52:58 pm
content: Since you didn't purchase the one as a working laptop is it possible that a former owner flashed the BIOS incorrectly? If you can get past this point then you might want to pull the mobo and look for visual signs of damage. An IC that has let all the magic smoke out will often have a burnt hole. You can also measure resistance at each large (often yellow) surface mount capacitor to ground looking for shorted supply lines. These cap's short out, but don't show visual signs of damage if the supply doesn't have a large current draw. Having a schematic can help greatly!

author: cdev
author_rank: Super Contributor
timestamp: November 29, 2017, 02:23:19 pm
content: Does it accept add on cards anywhere? I am wondering if here might be a laptop equivalent of the PCI POST cards they sell for PCS which will give you an indication of what is happening.Maybe there is a JTAG-like connection for diagnostics, a diagnostic header?If you had a fast logic analyzer, that might help you get info out? Is there a socketed BIOS chip? Maybe could you enumerate all the headers, or maybe upload high res photos of both sides of the board?

author: Old Don
author_rank: Regular Contributor
timestamp: November 29, 2017, 07:31:59 pm
content: Quote from: cdev on November 29, 2017, 02:23:19 pmMany of the Lenovo laptops follow the old IBM pattern of soldered BIOS chips plus will have a second chip with stored BIOS and boot passwords. Not easy to program the BIOS if the laptop is dead unless you have an external programmer and a new chip (or unsolder the old one).Unless the BIOS is total crap there might be a chance there's a BIOS rescue routine, but you'd need the service manual to know how to use it. Even then it's a crap shoot whether a new flash of the BIOS will help or not. You really need to look for blown components and/or dead power rails. Sometimes holding down a couple of keys on the keyboard would give you some error beep so you could tell if it was a video problem or a dead mobo. I used to repair laptops as a business and got out when OEM's started to make it hard to get parts from them. In the old days of BIOS sockets you could hot pop the BIOS out of working same model laptop and put in a chip in need of flashing and run the flash program. I did that before I got a better programmer that could handle all the (then) newer chips.Most video repairs IMHO are best with a new chip since so many bad video chips seem to get out into the wild. Yes, we will buy crap and continue to line up to buy again and again...... BGA = bad graphics adapter

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: November 30, 2017, 02:30:22 am
content: Quote from: Old Don on November 29, 2017, 12:52:58 pmI've checked all the obvious ceramic caps and many mosfets, no obvious shorts unfortunately. No exploded parts either.Quote from: cdev on November 29, 2017, 02:23:19 pmBios chip is not socketed, but I have removed them on my asus laptop to reflash it before, I have the tools.I'll look into getting some high res photos soon.Quote from: Old Don on November 29, 2017, 07:31:59 pmI might be able to swap the bios chip from my other board, but I don't know if it would be the same due to one having a DGPU and the other one not. Worth a shot I guess...

author: poot36
author_rank: Frequent Contributor
timestamp: December 02, 2017, 05:49:21 am
content: Out of interest what makes the i5 board totally dead and not repairable? If you can find the 3.3V and 5V standby rails on it you may have a shot at fixing it as well. Here is a rough power path of most laptops: Charger -> battery charger IC -> ultra low power always on 3.3V and 5V rails (less then 100Ma for powering the keyboard controller) -> keyboard controller turns on main 3.3V and 5V standby rails -> rest of system power rails.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: December 02, 2017, 08:07:34 pm
content: Quote from: poot36 on December 02, 2017, 05:49:21 amI wanted to have a non retarded charger, so I bought a cheap one off ebay just for the lead, and wired it in to a good quality 19v psu. But what I didn't check is that china had wired the end of the charger correctlyThis laptop uses a stupid 6 pin USB like charge port that can be used either for charging, or USB stuff. China had put the +19v and ground on the +5v and ground pins instead of the pins they were supposed to go toThe laptop now draws 0.000A on a correctly wired charger, no leds, nothing.A charged battery will not make the unit turn on either.

author: poot36
author_rank: Frequent Contributor
timestamp: December 02, 2017, 09:21:01 pm
content: Well that sucks. If you are lucky just the USB current limiting chip has been blown and it is preventing the laptop from turning on due to it thinking the USB port is drawing too much current and it shuts off the main 5V standby supply. I would check for a short on the 5V line. You may have trouble powering on the laptop with that lead because I think the laptop communicates with the charger to tell it to switch out of standard 5V mode and into 19V mode when it detects the laptop and not a USB cord has been plugged into in. I do know older Lenovo laptops used a 3rd pin to tell the laptop what wattage the charger is.