microsoft, vista, windows

HP laptop go-slow caused by power supply

175 Comments

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. 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

  2. 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.

  3. 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.

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

    Removing the battery the throttling gets the normal levels.

  5. Hi,

    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??

  6. 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.

  7. Hi,

    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 😉

  8. 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 ?

  9. 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?

  11. 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

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

  14. 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…

  15. 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.

  16. 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: http://www.shopping.hp.com/shopping/pdf/HP_ACAdapter_Compatibility.pdf)
    “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”

  17. 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.

  18. 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!

  21. [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.

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

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

  24. 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

  25. 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.

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