cross-posted from: https://infosec.pub/post/51012219
I bought an untested 2nd-hand HP probook 645 g1. When I plug it in, the power button just flashes. It does not look like an error code. It flashes every second or so. No long flashes and does not pause. It’s uniformly separated blinks that never stop.
It does this with or without memory installed. There is no hard drive but I don’t imagine that would stop it at least booting to the BIOS. I tried removing the wi-fi card and CD drive to ensure there is no problem to detect on those components. I also tried unplugging, removing the battery, and also detaching the cr2032 CMOS battery for some time. No matter what, the power button just blinks when it gets power. The power button is non-responsive.
What might the issue be?
One friend’s theory is that the machine is extremely fussy about the brand of PSU. I am using a Dell PSU to power the HP. It is 19.5v, as specified. So in terms of physics it should work. My friend’s theory is that genuine OEM HP PSUs give 19.51v (for example) and HP is somehow detecting that it’s not an HP PSU. Does that sound plausible?
14 Comments
over_clox@lemmy.world · 2 pts · 2d
OP, for at least the past decade, both HP and Dell have their own data sense pin, to declare brand, voltage and amperage.
They started doing this shit supposedly to circumvent the random dummy that would plug a 65 watt power block into a 90 watt laptop, only to burn up the power block.
Supposedly. But we all know its to keep you from using substitute parts and have to pay premium for original name brand...
daveyOsborn@infosec.pub · 1 pts · 1d
I appreciate the info. I’ll keep that in mind when looking for a replacement. I could only hope my problem is that simple but I don’t suppose that could be my issue because the HP probook 645 g1 is from 2013 or early 2014. It looks like a barrel connector with 2 pins.
over_clox@lemmy.world · 2 pts · 1d
I looked up the charger port for that model, and indeed it does have the center data sense pin. If by chance there's no center in in the charger plug, that means it's unfortunately been broken out, which is way too easy to do, and it won't work.
Hell, a little more on HP and their infinite wisdom..
The HP DV6 came out in 2011, and like other HP laptops of the time, were already using the data sense pin. The DV6 called for ~18v 90w, and we had an official 90w HP power block in our repair shop just for the picky HPs.
Well, we ended up with three HP DV6 laptops in shop all at once, and all three seemed to be complete bricks on our known good official HP power/charger block. But the customers swore their laptops were working when they brought them in, they were only supposed to be there for an operating system reinstall.
So, on a hunch, I suggested to the boss to have at least one of the customers bring in their original charger. And sure enough, they all worked fine on an original HP DV6 specific charger.
It was ridiculous really, even amongst HP laptops with otherwise exact same spec power blocks, HP laptops can be and are that freaking picky about exactly what model laptops their power blocks work on, no thank to that stupid data sense pin...
daveyOsborn@infosec.pub · 2 pts · 1d
Ok, thanks for the insight! I thought the center pin would be positive and the barrel exterior would be negative. But when I look closer at the Dell tip, it has two cylinder contacts plus the pin. And on the HP socket there are apparently 3 pins. Really hard to see the metal on the inside cylinder but I think it’s there.
What a mess. Now I need to know how to spot the correct PSU when I’m at the street market. I take it from your experience that it’s not enough to be HP with correct V and A. It must also be 3 conductor. But will that be enough, or might some be model-specific?
I have seen some universal chargers with 3 pins. I assumed the 3rd pin was so the tip could indicate to the PSU which voltage to switch to. Now I have to wonder if that also caters for HP or not.
over_clox@lemmy.world · 2 pts · 1d
Most of the HPs weren't quite as picky as the DV6, but they all insisted on being official HP chargers at minimum. And between Dell and HP, yes indeed many had identical physical connectors, so naturally you'd think if the specs are the same it should just work, but nope, not without the official blessing from the data signal.
Some models actually would work without a matching data signal though, but those models were few and far between, and they'd power on with a warning saying something like 'Cannot verify the connected power supply. Your computer will run at reduced performance to prevent from damaging your power supply or system'
But still, more often than not, if you plugged an HP charger into a Dell or vice versa, the system would basically just refuse to use it, so if the battery was dead, the system would just seem like it was bricked, but it just wants that data signal blessing to proceed charging and booting.
Winning@lemmy.world · 2 pts · 2d
Doubtful that it's looking at the voltage like that, the proper power cord probably also fluctuates from 19.5v more than you'd expect. What's the original amperage it's looking for and what is the replacement cords rating? You want to make sure the power cord you're using has a equal or higher amp rating than what the laptop requires. A good rule of thumb is amps are taken, so if the laptop says 1.5a it needs to be able to take 1.5a from the power cord.
over_clox@lemmy.world · 2 pts · 2d
Nah bro, OP's last paragraph is onto something that's actually been a thing for over a decade, they have a data sense pin to verify the power block. Check my other comment here..
https://lemmy.world/comment/25329457
daveyOsborn@infosec.pub · 1 pts · 2d
The Dell PSU I am using is 19.5v 3.34A. The reqs on the HP sticker are 19.5v 3.33A. I suppose that’s an exact match.. probably a question of whether they round up or truncate 3⅓A. I could buy an OEM HP PSU. On the big street market I go to it will be cheap enough, like 2 dollars. OTOH, I’ll be surprised if it makes a difference. I will just be wasting 2 dollars, I suspect.
partial_accumen@lemmy.world · 2 pts · 2d
This definitely smells like a power problem, but we haven't eliminated that your Dell PSU is actually fully functional yet, have we? Is your Dell PSU able to power up any other laptop successfully (with that laptop's battery removed)?
If your Dell PSU is otherwise functional, it feels like one or more power rail on the mainboard is nonfunctional/out of spec. This could either be from a failed voltage regulator on your mainboard, an on-board fuse being open, or possible a short to ground on one or more power rail.
I don't know your level of electronics knowledge or technical ability, but if you've confirmed your Dell PSU is otherwise good, then this is where you'd break out a multimeter and possibly a thermal camera to troubleshoot further.
daveyOsborn@infosec.pub · 2 pts · 1d
The Dell PSU has a white LED built into the cable end showing there is power -- a rare feature. That LED lights up with good brightness so I did not initially question the PSU. I just now attached a DMM which measured 300 mV. Another DMM measured 100 mV. So indeed the Dell PSU is bad.
Kind of a shame the LED is not designed to light up when ~19.5V is detected. I guess that might increase the cost too much.
I never used the Dell PSU before and have no other appliance for it. I happened to receive it along with other 2nd-hand stuff I bought. Thought I was lucky to have it once I came home with a laptop that needed it. None of my universal PSUs do 19.5v.. just whole numbers 19, 20, 21, etc.
Thanks for your feedback. Not sure how much longer I would have fiddled before deciding the test the PSU.
(edit) Now after insight from @over_clox@lemmy.world, I don’t know if the Dell PSU is broken. Perhaps the 3rd conductor which is used for data (to indicate brand-loyalty) is failing a negotiation. I wonder if it would send 19.5v if plugged into a Dell laptop.
(edit 2) correction-
This diagram for HP’s connector is apparently the same as that of Dell. So my measurements (100—300 mV) were bad. Metering the outer and inner cylinder yield 20v using a cheap DMM and no load. So the Dell PSU works and is likely sufficient in terms of physics.
over_clox@lemmy.world · 1 pts · 2d
https://lemmy.world/comment/25329457
daveyOsborn@infosec.pub · 1 pts · 2d
shit.. lemmy.world is in cloudflare’s walled garden so I cannot visit that link because I am excluded from their perverted idea of what constitutes a legitimate human being.. like I am undocumented trying to enter a right-wing restricted country. Is there a free-world cached version of whatever comment you are referring to that you can link for the general public?
over_clox@lemmy.world · 1 pts · 2d
It's just a link to the top level comment I left right here..
Damn, what's up with that shit? What Lemmy app are you using? 🤔
daveyOsborn@infosec.pub · 1 pts · 1d
I use the stock Lemmy client -- and that’s unrelated. The problem is you have chosen a centralised walled-garden (lemmy world) for your instance. You should switch to a less oppressive instance. This gives some background on Cloudflare:
I suggest infosec.pub. The admin demonstrates how to competently host a Lemmy server without excluding several demographics of people.