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Compaq Presario 1255 laptop charger polarity?

maelstrm

Experienced Member
Joined
Jun 6, 2022
Messages
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Location
Raleigh, NC
Forgive me for posting here, I think this machine is a P-II.

But could anyone confirm the polarity on a Presario 1255 power adapter? There's no indication on the label for polarity despite it having voltage and amperage. I bought an aftermarket but the tip doesn't even fit, leaving me in doubt. I have a universal I could try but I didn't want to flip the polarity coin without asking here first.

Thank you!
 
Let the record show that the Compaq Presario 1255 has a positive tip. This is likely the same for the 1260.
 
Easy way to figure out polarity on barrel connectors is to just do a continuity check from the center pin to the ground plane on the logic board. If there's no continuity, it's center positive. If there is continuity, it's center negative.

Only case this won't work is if it's a silly design that has a floating ground plane, but those are pretty rare.
 
Easy way to figure out polarity on barrel connectors is to just do a continuity check from the center pin to the ground plane on the logic board. If there's no continuity, it's center positive. If there is continuity, it's center negative.

Only case this won't work is if it's a silly design that has a floating ground plane, but those are pretty rare.
That's good to know. I wasn't up for tearing this one down though, was hoping someone had the same machine laying around.

But that's good to know for future reference.
 
You could probably do that continuity check against other ports that are exposed without opening it. Find any external metal and see if it is grounded to it.
 
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