Help Needed: Reverse Polarity Issue on HP EliteBook 840 G4 – Where Do I Begin?
Hi everyone, I recently acquired an HP EliteBook 840 G4 (6050A2854301-MB-A01) that I'm hoping to bring back to life. I'm fairly new to laptop repairs but eager to learn and willing to put in the effort to understand and fix this. Any advice or guidance would mean a lot!
What Happened
The issue started when the laptop was accidentally plugged in with reverse polarity. Before this incident, the laptop would show a power/charging light whenever it was plugged in. However, now it's completely unresponsive—no lights, no power, nothing. I've been doing some research and understand that reverse polarity can damage components like the protection circuitry near the DC input, fuses, MOSFETs, or capacitors. However, I'm not sure where to begin diagnosing and testing for potential failures.
What I Have
I've managed to find a schematic for the HP EliteBook 840 G3 motherboard. While it's not the exact model, I believe it may still be helpful since the architecture might be similar. I'm open to suggestions on how to use this effectively to locate and test key components on my G4. https://www.badcaps.net/filedata/fetch?id=3465844
What I've Done So Far
I am a teenager and complete beginner to laptop repair and know this may be challenging, but I'm here to learn. I'm interested in learning more about this vast field, so please feel free to explain things in detail if possible. Thanks in advance for any advice or insights you can share! Your help is deeply appreciated, and I'll do my best to provide updates on my progress.
What Happened
The issue started when the laptop was accidentally plugged in with reverse polarity. Before this incident, the laptop would show a power/charging light whenever it was plugged in. However, now it's completely unresponsive—no lights, no power, nothing. I've been doing some research and understand that reverse polarity can damage components like the protection circuitry near the DC input, fuses, MOSFETs, or capacitors. However, I'm not sure where to begin diagnosing and testing for potential failures.
What I Have
I've managed to find a schematic for the HP EliteBook 840 G3 motherboard. While it's not the exact model, I believe it may still be helpful since the architecture might be similar. I'm open to suggestions on how to use this effectively to locate and test key components on my G4. https://www.badcaps.net/filedata/fetch?id=3465844
What I've Done So Far
- Inspected the motherboard visually, but I couldn't find any obvious signs of damage (e.g., burnt components or blown capacitors).
- Started reading up on reverse polarity issues and common failure points like the input protection circuit.
- Checked if the board was receiving power from the dc jack – which it was.
- Where Should I Begin?
- I'm not sure where to start. What should I check first on the motherboard to see what's broken?
- Using the G3 Schematic
- I found a schematic for the HP EliteBook 840 G3. Is it useful for my 840 G4? How can I use it to figure out what's wrong?
I am a teenager and complete beginner to laptop repair and know this may be challenging, but I'm here to learn. I'm interested in learning more about this vast field, so please feel free to explain things in detail if possible. Thanks in advance for any advice or insights you can share! Your help is deeply appreciated, and I'll do my best to provide updates on my progress.
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