12-12-2017 08:23 PM
I have a Yoga2 13 model 20344 that will not boot up at all. The keyboard will light up and let me toggle the backlight on and off but the caps light will not turn on. I thought this was a bios error issue so I took the back off, disconnected the battery and desoldered a leg of the bios battery to default the bios... didn't do anything. I tried disconnecting everything except the keyboard, battery and display to test if another component was shorting out and still no change. I also tried hooking up the HDMI to an external monitor and it didn't work (I knew it wouldn't, but tried it anyway). No sounds are made by the computer at all.... I am thinking it is a bad motherboard but am open to any other suggestions.
Thanks in advance
12-13-2017 05:53 AM
Welcome to the Community Forums.
Seems it would appear more of a failed POST (power on self test).
You can try removing the harddrive and reapplying thermal paste to check if the display can still be recovered or at least the caps lock would respond. You can have it further checked for systemboard troubleshooting before deciding on full board replacement specially if the harddrive, RAM and thermal assembly works on another test laptop.
12-13-2017 07:21 AM
I already tried booting up without the hard drive connected.... not sure what you are talking about applying thermal paste to.... this model does not have the tiny hard drive (I can't remember what it is actually called)
12-13-2017 07:39 AM
Since there is no display even without the harddrive then it is probable that it is a No POST issue.
What I usually do is to clean the fans and reapply thermal paste/ pads as shown here in the hardware manual on page 41. Making sure that the CPU / graphic chip on contact with the heat spreader is not overheating or causing it not to display anything (requirement to complete POST).
Others techs consider reflow and reball techniques but such would require advance skills and tools specially if chip testing on the board seems to be fine. You can have it taken to a computer service center to confirm system board issue before planning on replacing it if needed.
12-13-2017 10:05 AM
Thanks for the tip... I don't have nor do I want to buy the equipment to remove/repair surface mount components. I will try putting new thermal paste where is should be... My first instinct was defective RAM, but there is no audible indication (not sure if there would be). Do you think it would be worth while to send it in for repair in lieu of just replacing the motherboard? Replacements seem to be pretty affordable ($200)
12-13-2017 10:39 AM
Yes, machines nowadays do not necessarily beep without the ram as they used to like beep code indicator.
Advantages of a service shop is that they have spare machine and parts to swap with aside from reballing tools if needed but considering labor and parts costing, it would be better simply replacing the board yourself after reviewing the modules if able.
Here is the hardware manual and service training module that can help you if reapplication of thermal paste and fan cleanup did not help. To get specific motherboard part number, you can get it from here.