Tuesday, October 26, 2010

Loose power jack repair for HP Pavilion dv7 series laptop

About a month ago, I started having power problems with my HP dv7 laptop. My first thought was that the power jack got loose over time since the problem seemed to correlate with the power plug being touched. Then I noticed that even if the battery wasn't charging, the LED mounted in the power jack would light no matter how I change the position of the plug inside the jack. Only the brightness of the LED had been changing a little bit. The other symptom was that the laptop would stop charging the battery while experiencing high loads. This led me to another assumption that the power adapter was probably dying and didn't provide enough power anymore. Unfortunately, when I tested my laptop with another power adapter, it worked perfectly for several hours which finally confused me.

I cut my power adapter apart in a brutal way, but everything looked nice inside. I tested all the capacitors with my multimeter and again everything was fine. I even dropped it on a concrete porch which we call "hit repair" in Ukraine :)

I ordered a replacement power adapter on eBay, but it didn't help a bit. All the symptoms remained almost the same. This is when I found lots of different forum posts and product reviews on Amazon/eBay where people were complaining that the new power supplies didn't fix their problem. Most interestingly, the number of complaints for the original hp chargers was no less than for the cheap alternatives.

Finally, I decided to disassemble my laptop to check the jack. I found very nice disassembly manual here, which helped me to get to the jack pretty fast:



The jack with the built-in LED



I disassembled the jack itself to see if anything were loose inside:



It turned out that HP didn't bother soldering all the metal leads to the wires which means that you get a 50% less reliable connection.

This whole part wasn't connected to anything!

Short piece of black wire provides the ground for LED
Taking apart the power jack is not necessary unless you want to bend the leads a little bit to improve connection.

Now, the root of my problem:

The negative wire from the motherboard doesn't even touch the lead

This has explained all the strange behavior of the laptop. While the negative LED wire was still soldered to the lead, the negative wire from the motherboard broke off of this same lead and was just merely touching it. I decided to solder the wires back to all the leads available to increase reliability:


(UPDATE: some of you were asking me how to figure out which wires go to which leads in the case you have many broken wires, so I'll try to explain how to connect them back. 

You should have six wire ends on the jack side and four on the motherboard side. The reason for that is two black ends are from a short piece of wire connecting negative LED lead to a negative jack lead (you can see it on the 5th from the top picture that I recently added). Now look at the 3rd from the top picture. You should have yellow (left) and black (right) wires connected to LED (very top of the jack). Make sure to check that you connect short black wire to LED, and not the one that goes to the motherboard (you might need to unwrap the tape a bit to the point where the short wire loops back to identify it). The remaining two black ends must be connected to a negative lead. Negative leads connect to the outer ring of the plug. There are two of them, and one is unused (as I mentioned above), it's the top left lead with the round hole that you can see on the same 3rd from the top picture, you can solder your two black wires there, or you can use the one that's symmetrically located on the right side to which the black wires were originally soldered at the factory, or both for reliability.

Red wire can be soldered to another unused lead, the one with the round hole in the middle of the jack on the picture, or the original lead to the bottom-right of the unused one. These two leads connect to the inner ring of the plug.

Finally, white wire should be soldered to a lead located in the bottom-left area of the jack. This connects to the center pin of the plug.

If you don't want to mess with soldering, you might consider ordering the whole assembly jack+cable from a place like eBay.)

Moreover, I took the opportunity to clean the heat sink (I circled the area where it's not cleaned yet):


Having cleaned the heat sink dramatically decreased the heat from the laptop and the noise from the cooler. In fact, it looks like it wasn't functioning at all before cleaning.


Overall, my laptop is working again without any power related problems. I saved on a new jack, and, what's funny, my original power supply survived all the tortures to which it was subjected!

11 comments:

  1. HI, I appreciate what you done hear by explaining your problems with you laptop. I have the same laptop and can't figure out what is wrong. When I plug in my power cord to the power jack it just doesn't charge but if I "wiggle" it around it works but when I let go of it, it doesn't charge. Do you think the power jack is loose and needs replaced? I have used 3 different power cords and it all does the same. If I would replace the jack with a new one would this product be the right one? Ebay item here Thanks!

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  2. Sorry for such a late answer, your message went to spam, probably because of the link to eBay, but if you are still having this problem... Yes, this is exactly the same problem that I had. The jack from your link looks like the right one. It's good that it comes with a cable, it will save you from having to solder it. You can google "HP DV7 disassemble". There is a nice tutorial with pics on the web.

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  3. You are the freaking bomb! Instead of paying to have my computer fixed this one is a no brainer & you solved my issue!!! Thank You

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  4. does it matter where the negative cord from the motherboard touches the dc jack... How do you where each color cord connect?
    HHeellPP??

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  5. I have the same problem i open my laptop and 3 wires was cut so i have the same question with Sirvant murphy what wire goes where there is any guide or screen shots to help me plz.

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  6. I updated my post with a discussion on how to connect broken wires back to the jack based on what I remember and the pictures I have. Let me know if you still have questions.

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  7. Thank you so very, very much. I am a 65 year old woman, you were so clear that I think I can do it myself. I am saving for a new computer, so why would I want to pay $175 to fix my DV7, I will let you know how I did. Thanks

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  8. hello there!
    Nice post here! I am interested in a pinout for that small power cable. I have HP Pavilion G6 too and unfortunately i don't have that small power chord, and i want to make it by myself. Can you help me with these?

    Thanks in advance!

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    1. Thank you for visiting my blog. Regarding a pinout, first of all it's hp dv7, not G6, and, unfortunately, I don't know for sure it their power cables are compatible. I can describe dv7 pinout here for you. First of all, the connector has a central pin, then inner ring and outer ring. There is a link in my post to the picture of a connector. Then, as you can see from my pictures, central pin is connected to the white wire, inner ring is connected to the red wire, and outer ring is connected to the black wire. Also, notice that there is a LED connected with a yellow wire to the motherboard and a piece of black wire to the connector's outer ring, but frankly, you don't need it for your laptop to function, so if you don't want to mess up with this LED, just forget about it. Unfortunately, I don't have a picture of the motherboard side of the connector, but you can google for it. For example, here you can see supersized images of all the connector parts, which is enough to know where to connect those black, red, and white cables to your motherboard, and again, you can ignore that yellow cable unless you want to use LED. Hope that helped.

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  9. In TEXAS "hit repair" is called "percussive maintenance". Enjoy reading of your work.
    Є день, наповнений подивом.

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  10. Thanks bro all i want was the led Connections ... i throw the jack and directly wired solder to my laptop ... froget about jack .. i dont need it ... the charger is always connected .. when the charge is full i disconnected my charger .. thanks that was helpful

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