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Chinese made aftermarket AC Adapter for [[HP DC7900 USDT Ultra slim Desktop]]. This adapter has no standard part number on the unit. The side has a sticker with YALL-2014-10 , S1135 . The main label on the underside reads: Replacement AC Adapter INPUT 100-240V 1.5A 50/60Hz OUTPUT 19V 7.1AVendor description: [http://www.smallacc.com/replacement-hp-482133001-ac-adapter-charger-power-supply-cord-p-2128.html Replacement HP 482133-001 AC Adapter Charger Power Supply Cord]* The inner ring (2) voltage tests: 19.63 VDC* The smart pin (3) voltage tests: 0 VDC (unloaded)The vendor claims the adapter will work with this computer. Connecting to the computer, system does not power on. This does not work out-of-the-box.This is one of many cheap Chinese made imitation products which sometimes work, and sometimes don't, because they do not test compatibility with all models they claim. However, if the adapter produces anywhere in the neighborhood of the correct voltage, and reliability, then it can be modified to work with your HP device. Often, all that is needed is a single 10 cent resistor and your willingness to void the warranty on the new knockoff adapter you just bought. It is much cheaper than buying the HP OEM replacement. An important consideration in purchasing your AC Adapter is that it will supply sufficient Amps. The amperage rating determines how much laptop or computer it can handle. This guy claims to be a whopping 7.1A which is plenty. It is a large unit which doesn't look like the one pictured in the advertisement.=== modification ===The smart pin was connected to a transistor. Disconnected from the board and using a 190K Ohm resister between the main positive voltage and the wire to the smart pin. This drops the voltage on the smart pin down near 5-6VDC.[[File:hpsmartpin02.jpg]]BLUE to WHITE - place the resistor between the blue and white wire.REMEMBER - The voltage will read much higher than 5 volts when not under a load. A resistor is _not_ a voltage regulator. The loaded voltage drops to 5-6 volts on the center pin when connected to the computer and the computer is operating.FINALLY - This is the correct relative resistor value for this particular computer system: [[HP DC7900 USDT Ultra slim Desktop]]. Other models including HP laptops have different current pulls, they are different loads, and therefore a different resistor value will likely be needed.