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. Had the same issue with an universal laptop charger with two wires output only. I took the output cable (3wires) from the broken HP adapter and made a voltage divider with two resistors (10k + 6,8k) to supply the central pin.
    Now my HP nx6310 laptop works like a charm!
    Thanx people!

  2. I got the same problem. After my original ac adapter from my nx9420 got broken, I bought first an universal adapter, than an cheap chinese one und finally 2 different original hp-adapter (90 and 135 Watt). But the problem is still the same – less performance with adapter: for example cpu usage: 1-4% without adapter; 5-12% after plugin ac adapter.
    Changing power management dosent help. I have no solution at the moment.

  3. Dell D630 has same issue with an old power supply keeping it at 789 mhz, new one let it run with fast no issues.

    I wonder how many people beat their heads on this one.

  4. I have a Dell Inspiron E1505 in my possession with the same symptoms seen here. I’ll be replacing the power adapter now with my fingers crossed.

  5. I Could solw this issue by changing the Power settings to Maximum Power ergo no Powersave.

  6. @Steve
    Let me know how that works for you. I have a Dell Inspiron 6400 with similar issues.

  7. Where can I set the power settings to high performance?

    First I repaired the normal power supply, it was broken in the cable, but the fix did not work. Then I replaced the powersupply by a cheap new one from “noname”.
    Also did not fix the problem.

    Now I have one option left and that is to “JUST CHANGE THE POWER SETTING TO HIGH PERFORMANCE AND ALL WILL BE O.K.”

    but where can I find this?

  8. Strange, I cannot find the option here.

    Windows XP SP3, does any one knows how to start the application using the Run command?


  9. One of my friend’s notebooks, a Compaq (HP)6710b has the same issue. For testing, I have just replaced the Power Supply adapter (including the cable & Jack assembly) with another one (actually with a little less Voltage and power rating but with the same kind of jack) that belongs to a Compaq NX 7400.
    Seems like it is working!
    Unfortunately, he had tried reinstalling, reformatting etc. and the PC needs a complete OS re-installation. And right now, that is being done.

    Looks like a Power Supply adapter replacement is necessary. I will later check for any defects along the cable/jack. The power supply box itself is completely sealed off with no screws etc. even beneath the black sticker (label). Will report the final status later.

  10. I had the exact same, i now have 3 replacement batteries. The problem was fixed 6 months ago but it has suddenly come back yesterday, this happened when the battery had got down to 5% charge, then i plugged the ac supply in and suddenly it all slowed to a halt. This time i have changed battery, power supply and everything i can but it is still too slow to operate now….. am confused whats happened

  11. I had a similar problem but based on the battery but with a Toshiba Sattelite L30 series.

    Laptop was being a right pig, while investigating somthing else, with the battery out I plugged it in again and it fired up right away, put battery back in and down it went again

  12. Thanks guys! You just saved me money! I appreciate your help. My computer had the problems discussed and when I called tech support, of course they suggested reloading. I did that and that did not solve the problem. Then they tried to sell me a $100 diagnostic service and, no doubt, that was just the beginning.

    I went in and bought an A/C adapter (the real HP McCoy) and it works like a charm. The folks at the store did not want to allow me to test a new A/C adapter insisting the problem had to be something else. After it obviously worked, they said “Hmmmm, I’ve never seen that one before.” LOL

    I bet I would have ended up spending $300 or more on this had it not been for you. You’re the greatest.


  13. I have an nx9420 and yesterday the laptop started to go at snails pace. I tried changing RAM and HDD but niether made a difference. I lieterally just found this site and read all the posts, so i just popped out the power supply and immediately the laptop sprang into life! Just to test I plugged the power supply back in and the screen flickered and it started to run slow again. Fortunately I have a spare AC adapter so Im ok.

    So a big thanks to everyone here as I was begining to think I had a very expensive doorstop!


  14. first of all I’d like to thank you for helping me diagnose he problem. Before buying a new one i wanted to see if i could fix this myself.
    I stripped the plastic covering on the plug and noticed that the soldering had broken on “the smart pin” irony? i wrapped the wire back around the pin re-soldered it.. all is working fine with minimal cpu usage! 🙂


  15. I also have the HP laoptop with the same issue, If I unplug the charger my system will work fine, if I plug in the charger then it will show 100% CPU usage. I tried the same charger on my friends laptop and in my friends laptop also it is showing up as 100% CPU usage.

  16. Same problem, I’ve a compaq nx7300,

    plus the fact that the battery drains quickly and loads slowly (all night pluged loads only 50%)!

    Is there a way to minimize the loading time of the battery ?


  17. I have an HP 6710b and also faced the same issue. I spent 2 days to find out the root cause of having 100% CPU usage before I realized that it is related to the power adapter. No hardware alarms, no software warning ….. nothing …. just having 100% CPU immediately after my notebook starts up. The funny thing is that I have to buy the 3rd power adapter for my 2.5 years old HP notebook. This is really a shame on HP.

  18. hi i have a big strange problem with a laptop of a customer
    it’s an hp 6730S
    it hangs at the HP logo with the message “press the esc key …..”
    when i press the esc or any key nothing happen . it hangs there
    i ‘m an electronic engeneer specialised in laptop repair ! so i have programmed the eeprom but the problem is the same . dismounted the laptop ,changed the processor , the memory , changed a new eeprom chip but the problem is the same.
    so i decided to reboot the laptop , to press the esc key and to wait . after 40 min it goes to the setup . i have tried every thing there but after rebooting the same thing happend and must wait for 40 min again to see it going to setup . i putted a virtual windows on a cd and after 40 min it boots on it and begins to load windows but veryyyyyyyyy veryyyyyyy slowly until it rises the windows desk …
    strange problem.
    can someone help me ?

  19. “Now I have one option left and that is to “JUST CHANGE THE POWER SETTING TO HIGH PERFORMANCE AND ALL WILL BE O.K.””

    “Strange, I cannot find the option here.

    Windows XP SP3, does any one knows how to start the application using the Run command?


    I have this same problem finding the correct power option. Is there a way to change the power setting to higher performance on XP, like on Vista?


    I was going mad with my HP Compaq 6710b. It was running all the time with 100% CPU consume, no matter what was running on it. Even simple applications like the taskmanager was enough to freeze it.
    Changing the charger solved the issue. Amazing…. Never thought this could be the cause.

  22. Same here-had a HP6910p and couldn’t figure out why the CPU was at 100%. Inadvertently took out the power supply from the wall and CPU dropped to 5%. Tried a new power cord and all alright now.Was about to do a fresh install-phew!!

  23. I had the same problem with a Lenovo Edge 13″.
    Changing the power adapter to an older (also 20V) I had in spare, solved the problem. Thanks!

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