HP laptop go-slow caused by power supply

Wasted some time recently looking at an HP Compaq NX7300 laptop, with Vista, that was running very slow.

No, not just normal Vista sluggishness. Really slow, as in you click the Start menu, wait a bit, and eventually it opens.

Temporarily disabled everything we could think of using msconfig (System Configuration Tool), still slow.

Checked the event log for disk errors, nothing wrong.

All very tedious as any actions took much longer than usual.

Found someone with the same problem on HP’s support forum here – but as so often with the Web, no solution is reported – though the guy does say, “can I assume that the cooling / cpu / power is defective”?

Called HP, and the guy diagnosed a faulty hard drive, though I was sceptical since his argument was that the self-test completed more quickly than expected, though it did not report any errors.

While scratching my head over this, I recalled that this laptop has what HP calls a “Smart AC Adapter”, which has an annoying proprietary connector featuring an additional central pin. According to this thread it actually supplies two separate power lines. The discussion includes this remark:

I tried to substitute the original HP AC adapter, with a general purpose AC adapter, applying a resistor divider between input cylinder- central pin-output cylinder, in order to get the second voltage.  But the laptop did not function normally: it was very slow

and someone adds

The slow function of the system with the alternative power source may be due to the system’s picking up a low voltage on the ‘monitoring’ pin.  This would indicate a low battery or weak charger and the system responded by cutting back on CPU/mainboard frequency to conserve power.

Could this be a clue? We started the laptop on battery power; suddenly it worked fine again. Plugged in the power cable, it slowed down. Removed the power cable, it speeded up again. Bingo.

New power supply is on order. It occurs to me that this could still be a problem with some internal connection, but I’ll be surprised if the new mains adapter does not fix it. Just occasionally the reason for a slow computer is nothing to do with Windows.

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175 thoughts on “HP laptop go-slow caused by power supply”

  1. Seems that the middle blue wire and the wire just outside the blue wire are conencting at some point. Making the voltages the same. Hence screwing up the power supply and causing the 100%CPU usage. So replaceing the wire should sort out the issue. Got my cuzn’s laptop and some dumbass soldered the blue and other middel wire together. So I undid his handy work an tada. back to normal.

    So give it a go.

    Peace out

  2. I just had this problem with a customer’s 6710b. I tested most components and noticed in Memtest, that the L1 and L2 Cache speed was way too slow – so obviously, the CPU was causing the slow performance. Luckily, at some point I tried a universal AC adaptor (Conceptronic CNB90) and everything was back to normal speed!
    What’s a little misleading, is that under Windows you will see some tasks take up a lot of CPU time – but that’s only because the CPU is so very, very slow under these conditions!

  3. We has also same problem with HP NX6320 model. CPU util was showing 100%. we break our head to find out the reason. Finally as suggested by you tried with another Adapter.Solve the problem

    Thanks a ton!!

  4. This is the exact thing the happened to me…. Until i realized that my computer was running in power saver mode!!!!

    Everything went back to normal after i changed it back to the “recommended” mode. hah!

  5. i just got my laptop after 3 months i started having speaker problem, two months after power adapter problem.
    it is no more charging my laptop. thought its under waranty.
    how do i fix this, because i dont expect hp to charge me for anything on that laptop that has not been used for even 1 year.

  6. Hi guys… this was a great help even I have a HP 6530s and the same problem persists that when i plug the charger(AC supply) the system goes slow and it says “plugged but not charging”… but unfortunately i borrowed a friend’s charger but even that didnt work… what may b the reason?

  7. One more here …. had the same problem with HP Compaq nx7400 … is anybody aware of a reaction from HP? Can you imagine how many thousands of laptops must have been replaced by people who aren’t that savvy or how many new power adapters HP sold thanks to this “well invented marketing tool”.

  8. Thanks to this site my laptop is now working, had worked out that it was a power supply issue but could not work out why! I cut the cable off and using a meter meter found the blue and +19.5 line shorted, managed to find the point about halfway down the cable! not at the point it goes into the supply. Before relising it was a PSU issue I hade reinstalled OS as I have thought this was a virus issue.

  9. Thanks guys, this post helped a lot, HP should do some user awarness on these problems. Or maybe take back all faulty power adaptors and give in a buyback new adaptors… Cheers

  10. I had the same problem with my HP nc6320. I can confirm that 100% CPU load with ac adapter is because of broken middle cable or damaged power source. In my case i had problem with slow response caused by broken cable (processor undervoltage), which i repaired (only with draging the cable) and measured the voltage on the middle pin. And of course before that i reinstalled my OS, disasembled my notebook and assembled again, put new cooling paste between CPU and cooler and so on… and the problem was in the f… cable!!!! :-))

  11. Thanks a bunch guys,I have a HP6510b which on battery was fine but connect ac and it slowed down by over 60%. Tried 5 different adaptors,from china,korea, Europe ,U.S. and Tawian. Thanks to you found that the only one was output 19v 90 watts 4.74amps with connector inside 5mm and outer 7.4mm.Paid $40 second hand,connected and WOW!!! so quick it was mindblowing

  12. I’m an IT administrator in a big company. We are using dozens of HP laptops. Since I work there (9 months) it happened at least 3 times. It took me really lot of time to figure out that the power adapters were to blame. After I replaced the power adapters laptops started to work fast like rockets. The effect was instant.

  13. HP 6910p – same problem here. I found it very suprising that a charger could do something like that.

  14. Hi everyone… I have the opposite of your problem. I have a HP Compaq nx9420 that goes fine while AC power is on, but the CPU goes crazy while in battery. Disinstalled XP OS and installed Vista Ultimate, and the problem is the same. Does anyone have a clue cause this is drivin me really crazy?

  15. I got same prob in my HP 6710 and when i unplug power it works fine and cpu back to normal so i chech along with charger caple i find part hot i unplug power and wait for 5 min then cut it with sharp cutter and i found 3 pairs of wire inside black 1 pair and white cover inside it one and blue cover the blue was touching the one in white so i use scotch tape and separate them well then i plug it works and after that will brought a new charger bcoz can’t count on this unless emergancy issues as i was in installation..

    Good Luck

  16. Hi guys, I have just had this problem on my HP ProBook 4510s which I have had for a while now, It has been amazing for me, since yesterday… I was baffled by this problem and thought it might of been something to do with my Processor, and of course that is proven wrong when I unplugged the charger as it worked fine again. I decided to try and use other methods which included plugging in speakers, microphones, all the USB ports with running peripheral devices such as keyboards, mouses etc. and nothing worked until I plugged in an ethernet cable from my Xbox. Since I plugged in the USB from my Xbox to my laptop, it has worked fine, the speed has recovered and there has been no problems.

    After finding the problem with mine I wanted to notify people and have just noticed it’s a very large problem… I urge you all to simply try plugging in an Ethernet cable into the laptop which is connected to a modem or router to see if this fixes the problem. It pains me to see people buying new AC adaptors when it could be fixed so simply, I will be happy if it helps just one person, this will of been worth writing.

    Good luck, Scott.

  17. I just went through this with a Compaq 6710b. I figured it out after while, but i still wanted to see if anyone had come across the same problem. It’s not something I had seen before. That’s when I found this thread.

  18. Having same problem right now with HP 6510b. Started seeing some issues like battery not charging, sometimes wouldn’t show charge indicator when plugged in, CPU gone at 100% usage and computer is slower than slow. Run on battery ok – plug it in then dead slow. now i changed my adapter then it work properly

  19. Unfortunately it’s only after you have a problem that you turn to the internet and discover what lots of people have already discovered.

    My laptop is a Compaq nx6325 which is quite a nice machine for its age when it has 2GB of RAM. I wanted to use it in the car for astronomy so got an 18V adapter to plug into the cigarette lighter socket. I put 18V on the centre pin and ground on the outside of the barrel connector. Nothing. I put 18V on the centre pin (white wire) and 18V on the inner barrel (red wire) and ground (black wire) on the outer barrel. The machine was charging but could do nothing because of 100% CPU. I then checked the mains power adapter and discovered there was about 18V on the centre pin, about 16V on the inner barrel and ground on the outer barrel. This is despite the label on the mains adapter saying it only has 18V on the centre pin and ground on the outer barrel. This is so annoying, I don’t think I can make it work in the car without a lot of messing about with electronics which I don’t want to do. Presumably HP/ Compaq is the only manufacturer that does this – is it really a good idea? I’ve already got through a stack of connectors and a pile of solder. It seems like a conspiracy to force you to use their power adapters.

  20. Hi, i have this problem of my laptop(compaq presario cq62) going slow after plugging in the charger including Audio/Video problems. i have changed settings to HP recommended..it seems laptop’s working fine. Thank God I found this thread otherwise i would have wondered about where the problem is and might have been formatting it 100 times till now. thank you million times 🙂

  21. well im glad to have read people with the same problem as mine, though mines not related to the power (i am not good with computers so bear with me) but i am nearly desperate to finding out what the hell is wrong why is this so damn slow (sometimes) that’s why i went searching for anything regarding the problem. Any way, i blame the internet provider or really slow connection, that’s affecting all to slow down (msofc, photoshop, slow opening other tabs/ going back to other tabs, i thought the movie i was playing was broken cause it was going green and pixelated but later on found out its the machines fault, not the movie copy. to make it short, everything horribly slows down. I was blaming the internet connection, but whenever i download or my brother downloads from his laptop, he says our internet is fast etc. so sometimes i blame the browser but i am not sure anymore what or why 🙁 can anyone help me out please?

    model: Hp pavilion dv7-4285dx
    i think this machine has good specs to slow like this, i have deleted almost all that i myself installed, i just have photo shop, cccleaner, firefox, mse installed, the rest of the programs came from hp. and to think hp was recommended to me, hp’s starting to piss me off ^^

  22. A start would be to start the Task Manager that comes with the windows operating system. To do this you press CTRL-ALT-DEL. Then it varies slightly if it is XP or Windows 7, but in either case you can get a list of the processes running and how much CPU each one is using. If there is one process that seems to be taking all the CPU it may be that there is a problem with that process or perhaps it should not be there at all.

  23. @Mary.

    Have you tried removing the battery and just running with the power supply connected.
    Its worth a try even though you say its not a power supply issue.

  24. Shame that no-one from HP/Compaq had the decency to comment here on this issue, even if ‘anonymously’.

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