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. Just bought an old 6190p with the same problem: When AC is connected (with or without battery) the computer behaves EXTREMELY slow – outside OS too. As soon as AC is disconnected it runs fine again. When trying to boot XP with AC connected there is a blue screen (unable to see error code) and then it reboots. Battery is charging very slow (or not at all) when power is on with AC connected, but XP says it is charging.

    I don’t think there is any warranty on this. The seller didn’t tell be about this flaw (I tested it outside without AC). I hope a new AC will solve issue..

  2. …forgot to mention: When AC is connected, CPU is constant loading – when disconnecting AC, CPU is not constantly loading.

    Strange or not?

  3. I have the same i have a HP 6510b i change the
    PSU by a new Original HP part and now im crazy because the laptop its equal but now if i remove the battery run fast with the PSU …..

  4. I have just had a hp6730b that was running slow. after tring all sorts of softare fixes I changed the power supply to a another one. Now all is working perfectly.
    Thank you.

  5. Same problem for me with an HP Compaq 8510w. System is 2.2GHz dual-core: running on battery the System Properties – General tab shows it’s running at 2.19 GHz. Plug in the AC adaptor – HP brand, supplied with the laptop – and re-open the System Properties dialogue, and it’s running at 789 MHz! No wonder it’s slow. Plug in a colleague’s adaptor from the same model, re-open System Properties – 2.19 GHz, same as on battery. I’m certain my problem is solely down to the AC adaptor.

  6. I have the same problem with HP Compaq nc6320. I think the reason is broken wire of the central pin. When curving the cabel neer the plug I can observe 100% CPU usage in some positions while in other the usage is almost 0%.

  7. I have HP nx9420. My old PSU have broken cord and is working seldom, but is working. My company ordered new HP adapter and when the new adapter is plugged in, the laptop gets really slow. I am hesitating to order new HP PSU since I don’t know if it is going to help and I am not willing to hassle with returning (through company).

  8. I just checked the voltage on my old PSU and quite amazingly the middle pin has 19.2V, and voltage across the plug is 19.8V (disconnected of course).
    Bare in mind that 19.2V may be due to wires (since they are loosing contact), but never the less with this voltages laptop is working perfectly.
    My new HP PSU that is not working has 7V on the control pin, and 19.5V across the plug. This sad, the PSU brick is almost exact as old one. Most of the specification numbers are the same with one notable difference. In the lower right corner there is a white square with code A01 for old brick and code A03 for the new one.

  9. Same problem with my HP nx7000. My friend and I bought same laptops on same day and in time of one year his adapter died, my died 2 weeks latter. Official dealer replaced adapters and now it works, but i have 100% cpu usage on ac and 0 on battery. Please someone help before i smash it in to the wall. 🙁

  10. Hi Friends
    I have HP 6510b running slow with AC i change the PSU by a new HP part know my laptop work fine with AC and Slow when its charging the battery , and run fine with battery but unplugged the AC . I charge the Battery at night with the laptop off , if U use the laptop with the battery 100% charged all work fine the tip its not discharge the bsttery because the charging sysmtem need to be resoldered in some spot or change some condenser in my work use the laptop witohut battery , and if i need use wih battery work fine only recharge with the laptop off. MEANWHILE LOL

  11. Hi! Same problem here. Laptop: HP NX6325. I managed to broke the original PSU and I ordered another one, having the same features (HP, 65W, 18.5V, 3.5A). Having the laptop running slow as hell, I reinstalled OS, modified power settings, and generally tried everything I can to make it run. After that I told myself I can’t be the only one, searched and found this blog.
    In addition to all facts related here:
    1. My laptop refuses to boot (no BSOD, just freezing) when the AC adapter is plugged in. So I use to start it on battery power and – after Windows starts to load – quickly plug in the adapter before battery completely dies.
    2. Windows reports the battery is charging, the complete charging will take about 12 hours. After complete charging and re-boot, Windows reports battery charged at 1%.

  12. My Compaq 6710b showed same same behavior — often very slow when plugged in, always fast on batteries. Thanks to all here for the education — that there is a third center pin for sensing, not power.
    Found a fix — Remembered renewing gold-plated plug-in card connectors by abrasion; so got a very narrow triangular exacto blade and scraped the sides of the small center pin at the end of the power cable. (unpowered, of course.) Power connectors arc a little and so renew themselves, sensing connections don’t.
    All seems better now; observed just one slow-down — fixed by rotating the cable connector a little.

  13. I have the same problem I bought 2 acadapter because first time that happened tough was the fisrt one and then I got another HP original brand and still the same, I have a R4000 compaq and running in battery is faster as usual but with the new adapter super slow!!!! I noticed also that the original adaptor the oldone that came with the laptop has 2 round filters coming out of the ac adapter box in the cableand the other ones do not have 2 filters only 1? I really dont know if this will affect the energy given to the processor? I need help letme know what do to do, thank U

  14. I have a dv9207us and the charging light comes on with a charged battery and the psu plugged and the system says charging but the battery drains. Also if I take the battery out and just try to power on with the PSU it will not work. Is this a battery problem or motherboard problem?

  15. I have a PS with a break somewhere in the cable. If I bend it a certain way, I lose power from the PS and it goes on battery. Otherwise the PS works and the Laptop works great. I took another PS (exact same model) from another Laptop (exact same model) and plugged it into my laptop and it then runs slow and high CPU occurs.

    Open Task manager and changed PS connections while monitoring the CPU. 1 PS, normal CPU, the other PS, high CPU.

    It is the PS that is the problem. Took voltage readings.

    PS that works good.
    19.44 V center pin
    20.01 V center ring

    PS that slow Laptop
    19.85 V center pin
    19.85 V center ring

    I’m afraid to order a new PS. What to do????

  16. NX6325 – with AC power on CPU is constantly 100% – works fine on battery – however battery does not charge – remains at 5%.

  17. after lots of troubleshooting and changing the PSU and opening the laptop to pieces – i concluded that it must be something wrong with the motherboard… not sure if it is worth replacing tough

  18. after reading through all the above posts – may I say that HP have some defective motherboards ….
    it seems to me that this is a common issue across several models of HP laptops. on battery all ok – on AC CPU 100% – but battery won’t charge – very very frustrating !!:(

  19. Hey everyone,
    I have the same problem my laptop is HP Compaq nx6325
    And my laptop runs so slow when on charge
    The problems is charger for me
    My charger as a V 18.5
    As when i go to my mates and use there HP charger it works fine!
    Yes, for people saying about buying cheap chargers from china and ect they don’t normally work
    It is very annoying because HP laptop chargers are much more money

  20. I have same exact problem here with notebook Compaq 6510b, it slows down very much on power, works fine when power in disconnected.
    when I check task bar on power, CPU usage is 100%.
    Did anyone find a solution.
    Thanks ?

  21. I have a Compaq 6710b with Vista Business. Under Task Manager, with laptop plugged in, 100% CPU utilization and nothing works. Unplug the power, all is fine. Is this a VISTA problem,power problem or HP problem? My power cord is flaky, need to reposition it to get juice and have ordered a replacement just waiting for it to arrive.

  22. I had exactly this problem with my hp8510w meanwhile hp replaced (in 2 months):
    – 2 times the mothercard
    – 2 times the graphic card
    – the processor
    – HDD
    – DVD
    and … The ddram.

    The pc was also sent to HP headquarters in Japan.

    Ok finally a new charger is coming next week.

  23. Just a last detail: the pc was extremely slow running any OS (Fedora 10, vista and the last Windows seven..)

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