Repair of a dead HP 250 G5 laptop (LA-D703P motherboard)

Here's another computer motherboard repair, this time with a schematic, and featuring a fairly common fault. But what at first appears simple, is not always so - for hidden surprises often lurk in plain sight, and that which seems a red herring, can turn out to be the catch of the day... 0:00 - Introduction 1:00 - Note on power supplies 1:35- Power test, a white light is a start 2:03 - What next? Let's refer to the schematic 3:35 - Do we have the main 19v rail? 4:44 - Do we have our standby rails? 5:15 - Where are the standby rails on this thing anyway? 8:50 - Is the power button signal working? 9:54 - A clue that burns a hole in your pocket 10:15 - Alcohol helps make faults talk 10:41 - When things start heating up, we check for shorts 13:13 - A short circuit is found, let's turn up the heat 14:54 - Closing in on the culprit 16:31 - Narrowing it down with another drink 17:13 - Target acquired 17:47 - So, which capacitor is this, anyway? 19:49 - Removing the suspect 20:00 - Verifying the short is now gone 20:35 - A quick power up test & checking voltages 21:23 - Let's do a proper test with the LCD connected 22:28 - Fanspin! That was easy. Too easy... 22:59 - Maybe it needs everything connected. Maybe? 24:05 - Let's check the little things, CMOS battery, etc... 26:10 - A flicker of hope? 27:00 - Flicker II: The Flickering 27:42 - Swapping RAM sticks in desperation 28:08 - If the LCD doesn't work, what about external video? 29:04 - HDMI brings some operational clarity 29:25 - Supply rail shenanigans 32:16 - Back to square one? Or in this case, Q21 34:30 - Two Months Later: Government interference? 35:40 - Unpackaging, ESD concerns & unanswered questions 38:48 - Evicting the faulty culprit 40:29 - Cleaning up and preparing the pads 41:42 - Installing the replacement 44:35 - Cleaning up again 45:11 - Inspection by the oblivious 48:02 - Flicker III - A New Flicker 48:54 - Almost there? Or is Murphy just out for lunch? 49:56 - The solder paste that didn't 50:37 - Re-testing again with a good poke 51:21 - It's The Final Reassembly 52:20 - 3... 2...1... We have BIOS! 55:22 - Bonus Question - What is the sound of one hard drive dying? 57:53 - It powers on, but can it run Memtest? 58:35 - Conclusion -------------------------------------------- | Repair Notes | -------------------------------------------- Laptop Model: HP 250 G5 / W5T32PT Motherboard Code: LA-D703P Rev 3.0 - 2016-09-14 Problem #1 Symptoms: Charger light comes on, standby rails OK, but laptop will not power up Fault: C48 shorted on +3VS_CRT_DVDD, derived from the main +3VS rail. Solution: Replace C48 (10uF 6.3v ceramic) & increase voltage rating to 10v for future reliability Problem #2 Symptoms: Laptop now powers on but screen only flickers & has no image. Fault: Q21 damaged from overcurrent on +3VS rail, +3VS rail is low (~2.5v) Solution: Replace Q21 (EM5209VF dual MOSFET load switch) -------------------------------------------- Music: Unicorn Heads - Digital Secrets (From YouTube Audio Library)    • Unicorn Heads - Digital Secrets