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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167 comments to HP laptop go-slow caused by power supply

  • Conrad

    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

  • Oliver

    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!

  • Jojo

    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!!

  • liz

    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!

  • abigeal

    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.

  • Harpreet

    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?

  • Jan

    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”.

  • Mike

    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.

  • Vipul

    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

  • 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!!!! :-))

  • John Suddards

    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

  • Jakub

    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.

  • Android developer

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

  • Elton

    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?

  • Mahmoud Elenany

    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

  • Scott Martino

    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.

  • Paris

    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.

  • muhammed ckt

    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

  • Andrew Bennett

    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.

  • Suvi

    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 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 🙂

  • Mary

    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 ^^

  • Andrew Bennett

    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.

  • John


    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.

  • psm


    I need pinout for HP nx920 batery 14.4V 73Wh.

    Thank you.

  • MikeW

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

  • Khalid Alamir

    I have hp compaq 6730s ,several days ago I start facing the slow performance of my CPU while connecting to the power adapter I just have been waiting until it fully charged and unplug it and continue using my laptop normally but I surprised since yesterday that the charging itself goes very very very slowly do one beleave that I put my laptop in the charger befor 20 hours and now the powermeter speaks about 24% charging level, I read all above and I find most descutions pushing to changing the adapter but this will made me mad cuze I recently buy the current one

  • Bzangor

    Try unplugging the power supply from the wall (not from the laptop) for a few minutes… After messing with mine all morning, every time plugged in the CPU would spike to 100% bogging the system down; I unplugged the power supply from the wall for a few minutes (cooled down maybe?) and after plugging it back in the battery is charging and the CPU usage is now at ~8% for the last couple of hours. Not a sure bet, but worth a try before replacing an expensive adapter.

  • André Torres

    Ok, HP TM2 1100 / 8GB – 500 Hybrid HD – Same as you guys, I am getting the AC BUG, this is totaly unexpected. Have you guys ever noted by CPU-Z, when AC power is connected, the CPU is cutting the multiplication factor / note from 12x the processor is delivering 2x, 3x. I believe this is the reason the processor is getting top levels handling very small jobs, without heating the CPU.

  • André Torres

    “one more thing” HP TM2 1100 – 8GB + AC BUG

    Removing the battery the throttling gets the normal levels.

  • viant


    Good to see that someone has the same problem.
    But you didn’t tell how to solve the problem.
    Was changing a power supply help solving the problem?
    Did the power supply cause the problem? or the battery? or something else??

  • Alex Petit-Frere

    I have a Gateway M-6340u and I have been experiencing the problem of my laptop running slower when the AC adapter is plugged in as oppose to when it is not plugged in also. Some issues include my mouse on my laptop not working, my browsing becomes much slower and some of my pages never end up loading. As soon as I unplug the adapter, everything goes back to being normal. This has been happening recently But this only occurs while I am on a WiFi network because when I use an Ethernet cable using that connection instead while it is plugged in, It runs smoothly. I don’t know if the problem is with the AC adapter or the battery. I was considering buying a AC adapter but I don’t know if that would solve the problem.

  • bbcy


    I’m admin at a large company and one of my users had the same issue as described here. Haven’t found a solution or even a reason for this but maybe it’s still useful for someone to read this:
    I can confirm it’s the power supply, I tested it with half a dozen laptops (HP 6930p with and without docking station). It’s not with the wall plug (as said in HP forums). It’s not a software issue (not Windows, Virus, etc), don’t waste your time searching for this. The CPU itself seems to be the issue, though I checked with CPU-Z and it constantly showed ~2,4GHz (always “High performance” power plan) which it wouldn’t do if throttling would kick in. But I still think it may be some kind of CPU throttle as stated by André Torres, probably CPU-Z doesn’t work properly on my specific system (we have a very customized Windows here) or it’s not the multiplicator but something else.
    Note that after everything I read this is an HP-only issue (Compaq of course as well), no other laptop behaves like this even with bad power supply.

    Hope this helps others not to waste time searching for defective components or reinstalling Windows 😉

  • Adrian

    Hy guys , i have a problem…. i have the same problems that u guys are talking here about, My HP Compaq 6910p goes of AC its working fine , still it isnt working on 2100 Mhz , just 1600 Mhz. I have a Core2Duo 2100Mhz; If i Plug in the AC ADAPTER the computer is goin at 1600 Mhz. I have replaced the thermal past from the processor and still same problem… Sincer this problems , it has never run at 2100 Mhz. What can i do ?

  • jlex1208

    I’m having the exact same symptoms, but my problem appears to be the building and not the adapter. I have an HP 6390p and when I plug the adapter in, the system speed comes to a crawl. I bought a new HP OEM (not knock-off) adapter and the same thing happens. However, unlike the problem that most have experienced, when I bring my laptop home and use it with the adapter plugged in; it works just fine. In fact, both the old and new adapters work just fine at my home and the both cause my laptop to come to a crawl at my office. Therefore, I am guessing that I have the same voltage problem, but my problem is the building and not the adapters. My first question to the community is what can I do about it? Is there a product the will raise the voltage or do I need to go through the building owner to test and and raise the level to a ‘normal’ operating level? Also in this same office, I have 4 desktops, 2 small laser printers, and an HP ML370 G6 server, plus a switch and firewall. None of these machines are having the same issue, but I’m assuming none of these have the technology that is in the ‘Smart Adapter’. My second question is that even though these other machines are not showing problems, will low voltage cause problems for these machines over the course of their expected lifespan. That is, will it burn them out faster?

  • memin

    This post was awesome, it fixed the slow CPU motion. Thanks!!!

  • shaan

    i have a laptop hp dv6 paviilion it is working fast when power cable is connected when i use battary backup of my laptop it is going slow anyone help me how to fix this issue

  • jay

    hi i have hp nx6320 laptop i purchece new battary and adapter but laptop can’t charge properly plz give me the solution

  • Most of the time, its the connector and the tip of that cord which are causing the problem, so just order a replacement connector from eBay for like $4 and you’ll have your adapter in perfect working condition.

  • MMM

    Another problem with HP laptops is the battery. I just bought an used DV3000 that the previous owner was selling because it was running incredibly slow. Thankfully he included two batteries: the original one, which was spent, and the replacement one. After two days of tinkering, I finally discovered that the replacement battery, which was a cheap copy, was causing the issue. The laptop ran just fine without the battery, or with the original one installed, even if it was bad. I always try to save as much as possible in replacement parts, but in this case I’ll have to go with genuine, sigh…

  • crisco

    compaq presario v2000

    thanks for the tips. bought new power adapter and still had plug-in slow-down problem, but fine in battery mode. ackpth.

    issue was battery/power management. weird.

    Power Properties was set to ‘Minimal Power Management’, and i noticed that ‘Plugged in’ settings were set to never turn off, whereas the battery settings had various time values. i created a custom setting where the plugged-in values matched the batter values and compu was back to normal. not ideal if e.g. i really didn’t want things to turn off after time, but fastest D/L and processing speed matters most to me now– with this old lappy. maybe i could monkey with the time values and set them really high, but i’m tired of this. i barely even wanted to write this pargraph here, ha!, but i hope it helps someone.

  • Josh D

    Anybody wondered if this was a wattage issue? My HP laptop (core i5) came with a 65W adapter, and show the same traits: runs well when not charging the battery, but if the battery is charging, my CPU frequency drops to sloooow. I can see on the Win7 resource monitor that CPU frequency is 20% (of a nominal 2.4GHz). I’ve talked to HP and they are sending me a replacement 90W adapter. When it comes in I’ll try to update and let you know if that fixes it.

    Food for thought: here’s a disclaimer on a PDF that HP has on adapter compatibility (found here:
    “HP Smart Technology computers are designed to vary performance as needed when a smaller capacity Smart Power Adapter is connected. Resource intensive tasks may cause your system not to perform at its highest level with a smaller capacity Smart Power Adapter. Connection of a higher capacity Smart Power Adapter may be required for full performance”

  • Matt D

    Wish I had found this a couple weeks ago…been going insane trying to find what was causing this very issue in my PC. I finally figured out on my own that it was the power supply…but the cord half causing the issue…not the brick half. It was so perplexing…It would work perfect at work in my docking station…but when I was on the road or at home it would slow to a crawl and make it impossible to work on. At first thought virus…then I thought something with the docking station since it work at my desk…tested that out with the docking station at home but didn’t work…then I had a aha moment when I relaized the common thread of when it wouldn’t work…in all cases was I always had my power supply I use at home and travel with…I started to test that and what do you know…I found the issue…It was really hard to find the solution online to this as well…never seen this before…once I replaced that part of the power supply it started working again…just like it should.

  • Josh D

    Hey again. My new 90W adapter came in the mail today, and I tested it out by draining some of the battery and then plugging the adapter in while running Prime95 and keeping an eye out on the CPU frequency. The 90W adapter works like a charm and can both keep my CPU speed up and charge the battery at the same time. I even switched the power cables of my two adapters to see if that was the problem…nope, it was a simple matter of power consumption.

    So next time folks, when you buy laptops, beware if they send you a 65W adapter…your computer will be crippled if it’s charging!

  • Elena

    HP 6730S with the same problem, also due to a faulty power adapter.

  • crezent rion ritez poblete

    so in other words? what are the syptoms of faulty PSU?

  • ohmy

    [aaaaahrg so many people going crazy about this and I thought I’m the only one..]
    HP NX6325 here. Used a LEICKE PSU, original PSU got damaged. What I tried after reading all this, is to curse HP, didn’t work. but what seems to make things better, is to bend the midle sensor thing at the laptop-end of the PSU a little… but maybe I’m just starting to imagine things.

  • ohmy

    did I mention that my battery is so low, that I’m unable to try if it works on batterypower…

  • Chinook

    Thanks for the post, it fixed the slow CPU problem. Just want to thanks once again!

  • harry

    thanks so much. i got this slow issue for long time and cost lot of effort to sort it out. find the problem now.thanks

  • Ibañez

    The same problem with the hp 6730s.

    With power connection, very very slow, also in bios test mode.
    Without power connection, only battery, it’s work fine.

    It’s crazy.

    Thanks for the post.