Diagnose Motherboard Laptop HP 15 series

[Calculici]

Hi,

I'm new to diagnose and repair of laptops so bear with me.

I have a HP 15 G092SA laptop which refuses to power on. The light at the end of the DC Jack is off. I disassembled it and started taking out all the connectors like I would do with a normal desktop just to see if there is something wrong with it. My surprise was when I took out the connector from the LCD screen to the motherboard the light of the DC Jack was on. My next action was to take the laptop and stick it to an HDMI cable and to my surprise it works.

Now my question is: How do I diagnose if it's the motherboard, the motherboard connector, the LCD harness or the LCD itself that doesn't work.

Thank you very much for your help and input.

 

[cowboybob]

My first thought was that the backlight (or its driver circuit) has failed. I have found HP laptops (I've had three) to be prone to all manner of internal power problems.

As for diagnosing the exact problem, sort of depends on the availability of spare modules (i.e., LCD display and motherboard or an appropriate backlight).

You might check the LCD harness connector's LCD pin that provides power for the backlight for the correct voltage, if (and it's a big IF) you can discover the connector's pinout arrangement.

Alternatively, just get a small TV (with an HDMI connection) and use it for your monitor.

 

[Calculici]

Thanks for your answer. I will try to find out the PIN arrangement for that connector. I don't want to change for example the LCD screen and find out that it is actually the motherboard. I will come back with feedback.

 

[Mark G. Cooper Sr.]

Greetings Cal !

If you still need some hints to correctly diagnose your problem I am happy to assist you. It sounds to me as though you have a bad LCD display, inverter or LCD cable. You can narrow it down somewhat by carefully removing the plastic bezel surrounding the LCD display and then loosening the display from the lid and temporarily disconnecting the LCD cable from the LCD panel and see if your power indicator comes back on. If it does, the LCD display is bad. If nothing changes, next, temporarily disconnect the inverter, again noting if your power led comes back on. If it does, then suspect the inverter is the culprit. The fact that you do have correct display output from the HDMI output tells me that the motherboard is not at fault.
I have repaired laptops for well over 20 years and these are the steps I recommend to find the offending cause of the issue. Hopefully, by now, you have already discovered your problem since it has been some time since your original post. You may keep these troubleshooting tips in mind for any future adventures into laptop troubleshooting, they are universal tips for all laptops regardless of make or model.
Best regards, Mark..