Hi, i got a hp compaq mx7400, i dont hame the charger so i want to open the laptop and connect direct a different adapter to the chargig block. i dont know which pin is positive and negative

Adapter arrived promptly, but did not have a "dongle." Seemed to work well for about 6 months but then did not charge laptop battery and only worked plugged in. Eventually a computer technician friend pointed out the adapter was too light to be real - compared my original adapter it weighs about half the weight. Not very impressed and would not recommend. I have no complaints about this item whatsoever, for all intents and purposes it does everything my original AC adaptor did.
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Take the battery out, plug in the charger and see if the laptop works. If it works, the battery may be the problem. Check the AC Adapter
Check to make sure the adapter is plugged securely into the wall outlet, connected firmly to the adapter box and to the back of your laptop. Most AC adapters have a little light in them on that rectangular box in the middle of the cord that lights up when it's getting electricity. If that light isn't on, try a different outlet. Check your fuse or circuit breaker box and plug a different device into that outlet to make sure there is power to it. If it still does not light up, your adapter could need replacing. Also check the adapter box for signs of warmth, as it will generate heat when it's plugged in. No heat means no power.

Remove the Battery Sometimes it's as simple as a seated battery. Remove the battery entirely and clean out any dust, lint or hair that may be clogging the connectors and preventing a proper connection. Reseat the battery securely and make sure the little locking pins that hold your battery in place are securely fastened and there is no movement.

Hi Jon. it sounds like the DC power jack needs fixing or replacing.
go to this link and scroll down the page and have a read up.

laptop charger port hole broken Google Search

According to your description, there is a big chance that you charger need to be replaced.http://www.chargerbuy.com/replacement-hp-compaq-nx6320-smart-ac-185v-35a.html

Both 65w and 90w ac adapter will work on you hp compaq 6710b laptop, and do no harm.
http://h71016.www7.hp.com/html/helpmechoose/nboptions/adapters.html

http://www.chargerbuy.com/replacement-hp-compaq-6710b-smart-ac-185v-35a.html
http://www.chargerbuy.com/replacement-hp-compaq-6710b-ac-adapter-19v-474a.html

IF the battery is bad the charge lndicator on the laptop will flash (But not periodically) it will be a constant on-off-on-off..... Best check would be to remove the battery completely and use the adapter/charger power supply only. If it still does not turn on then you either have a bad power jack connection or a more serious motherboard problem. Also is the green light flashing on the adapter/charger or is it the charge/battery indicator on the laptop?

Hi.

First ensure that the wireless adapter is turned on.

If the adapter is on and does not detect any network, reinstall wireless network adapter drivers. the drivers can be obtained using the link below.

Download drivers and software

Reinstalling driver software usually fixes the problem, if it does not it usually means that the internal adapter is defective, in that case you will need to use an external wireless adapter (USB).

Is this the same if the charger is also plugged in??

Remove battery and retry with charger plugged in.

If same battery charger is faulty.

Best thing to do is try a new charger, if this dont work then you will need to have the a/c adapter changed

i thibk the charger head went out thats what happend to my gateway just cut the part of the charger that goes into the computer (if its not the prob u can fix it back later) cut it open and see if any of the wire has broke off if so use a soutering iron (i dont know how to sourtering)
and some souter and souter it back on thats the best i can help

ps i done this to my gateway labtop and it worked fine