Read the label on the computer [dunno what a DV9000 is...] where it indicates the power it takes to operate & charge the battery. It should have a symbol like a large letter "C" with a small dot in the middle. The labels should indicate which is + and which is -, and the voltage supplied. Using this information, take a VOM and read the voltage on the AC adapter connection with the adapter plugged in. There should be voltage produced of the form, AC or DC, indicated on the label, and of similar voltage. Most chargers will operate a bit above the indicated voltage to be able to charge the battery while the unit is being used.
If the adapter doesn't generate the proper voltage, it is likely defective. Some have user replaceable fuses, some don't. You could also have defective wires leading from the charger to the computer. Many times the wires get flexed near either end so often that the strands of wire break, and lose conductivity. In that case, you could check the wires for continuity.
tom
I had the same problem on an older DELL. Not sure if it applies to the HP dv9000, but some of the older DELL laptops have a chip in the AC adaptor that burned quite often. This chip is needed by the laptop to charge the battery. I simply bought a new charger that solved the problem. You may want to try a new charger first. See post: https://www.badcaps.net/forum/showthread.php?t=6912
Check that the DC connection on the laptop is good. i.e. that the center pin is not bent or that the part has not come loose. You may have to open up the laptop to check this.
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