HP EliteBook 840 G3 not charging. - Page 1
Forum section: electronics / repair

author: Riq
author_rank: Contributor
timestamp: June 05, 2025, 11:07:52 pm
content: Hello there.I currently am troubleshooting an HP EliteBook 840 G3 (yeah, pretty old) with the board no. 60502728501-MB-A01. The AC Adapter is providing 19.8V and the board is getting that same voltage. The charging IC is a BQ24780S. ACOK pin (5) is working properly, but I do not see anything happening in the PHASE pin (27) or any of the pins driving the MOSFETs.Another thing is that the laptop charging LED blinks 9 times (white) when I plug it in.If someone could give any advice on what should I do next, please do not hesitate. Anything is appreciated.Also, if someone knows where I can get a schematic for the MB stated above, I'd be pretty grateful.

author: elektryk
author_rank: Regular Contributor
timestamp: June 06, 2025, 11:42:14 am
content: Is your PSU properly recognized?This one probably has a connector with an ID pin.

author: Riq
author_rank: Contributor
timestamp: June 06, 2025, 04:26:30 pm
content: Quote from: elektryk on June 06, 2025, 11:42:14 amShould this ID pin be high or low? How else can I check if it's properly recognized?

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 06, 2025, 05:37:30 pm
content: I just had to upgrade from an EliteBook 840 G4, which is quite similar, but I don't do actual repairs (just a hobbyist).TheHP Maintenance and Service Manual for EliteBook 840 G3and others may be useful. It isn't board schematics, but you can still get replacement parts (if not from HP, from AliExpress/eBay).The DC power connector (male on the power brick cable having 4.5mm outer dameter, 3mm inner diameter, recessed pin; almost always with blue plastic ring in front) female side is a cuboid plastic piece with sturdy metal legs surrounding it, and it is soldered into a recess to the motherboard. To remove or replace it, you need to carefully shield nearby components from excess heat and use hot air to desolder it; you can find videos on Youtube on this. Anyway, one failure pattern is such that when the power cord is yanked to the side, the recessed pin support/receiver in the laptop side connector can break, and no longer make a good connection. The only solution I know of is to replace the DC connector. Fortunately they're cheap and easily available at AliExpress.The problem often shows up as the laptop not charging, sometimes able to draw current but only for a few seconds, with borderline cases (like mine) sometimes working if the DC connector is pushed a bit in some specific direction.Replacing the DC connector on the laptop board is then paramount, so that the partially connected connector on the laptop board won't break the PCB too: as far as I know, a broken PCB near the DC connector means that board has to be replaced. (I have the parts and know how it should be done on my 840 G4, but my rework-fu isweak. I can solder up to TQFP, but BGA and rework scares me.)Also note that a lot of HP laptops use the same two power bricks: "65W HP Smart Adapter" and "45W HP Smart Adapter". Both work with 840 G3.The nine blinks –– specifically, 8 slower blinks and a fast blink –– indicates a failed power brick or failure to communicate with the power brick, so if you've verified the brick is okay (with another HP laptop), I'd be very inclined to suspect the DC connector on the laptop side, because of the innard pin issue. If you look at that female connector, you should see a tube (or a pillar with a hole in the center) recessed in the connector. If it is not centered, or wobbles if pushed, it's gonski. However, even if it looks and feels okay, the connector can still be børked, so better replace the connector if you are able.

author: Riq
author_rank: Contributor
timestamp: June 07, 2025, 01:54:26 am
content: Huh. I thought that my adapter was good just for its output. I'll try charging another laptop with it just to be sure. Thanks for that info.

author: elektryk
author_rank: Regular Contributor
timestamp: June 07, 2025, 07:03:37 pm
content: Quote from: Riq on June 06, 2025, 04:26:30 pmIn older models with black connector there was some resistance between ID and positive terminal, but as long this brick works with other notebook, it should be ok.Check connector on notebook side as Nominal Animal said.