Both power supplies output 19.5 volts which is good. But the old Dell power supply only puts out 3 amps, where as the hp puts out more.
The dell cannot put out enough power to supply the needs of the HP - it will probably work for charging the battery while the laptop is switched off but will overheat and burn out if you were to use it for anything more.
Also some dells and hp power supplies have genuine parts authentication chips in them and will not work when being used with a different brand of laptop.
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