Laptop power polarity?

[Calab]

I have a Gateway T-6815 laptop. The power brick was lost so I've purchased a
generic one. Unfortunately the laptop doesn't show if the tip is positive or
negative.

The only diagram is:
____
19v ----- 3.42 A (That's a dashed line under a solid line)

Does anyone know how to determine the polarity needed by the laptop?

 

[Guest]

If you open the laptop

Shouldn't have to open the laptop. I've never seen one that didn't
have some kind of ground exposed to the outside. Shield of a usb port,
other I/O connector etc.

and check continuity between a common

 

[UCLAN]

I have a Gateway T-6815 laptop. The power brick was lost so I've
purchased a generic one. Unfortunately the laptop doesn't show if the
tip is positive or negative.

The only diagram is:
____
19v ----- 3.42 A (That's a dashed line under a solid line)

Does anyone know how to determine the polarity needed by the laptop?

Look *closely* at the area immediately adjacent to the power jack. Every
device I've seen that uses a "wall-wart" had some sort of designation,
like a "O" with a dot in the center, with a "+" and a "-". Generally
speaking, the center post (the dot) is positive and the surrounding
ring (the "O") is negative.

 

[John McGaw]

I have a Gateway T-6815 laptop. The power brick was lost so I've
purchased a generic one. Unfortunately the laptop doesn't show if the
tip is positive or negative.

The only diagram is:
____
19v ----- 3.42 A (That's a dashed line under a solid line)

Does anyone know how to determine the polarity needed by the laptop?

A company which sells a "direct replacement" for that PS shows the tip as
being the + terminal and the sleeve as the negative. What gets me is why
you need to know. If you bought the correct power supply then it is, well,
correct and you shouldn't have to be bothering with the polarity. BTW, the
direct replacements I've seen are dirt cheap at < $20.

http://hqrp.com/HQRP-Replacement-19...froogle&utm_medium=organic&utm_source=froogle

 

[John McGaw]

Are dirt cheap generic relabled PSU a safe option? IMO,
better to find the OEM part # to get an exact replacement
than risk a laptop, they might be available fairly
inexpensively on ebay.

Is getting an exact OEM replacement better than some unknown and unknowable
unit? Sure. But it is possible that that OEM unit will have been made in
either the same Chinese factory as the unknown. Or maybe in the one next
door. Switching power supplies are such a commodity today that the
differences are subtle and difficult to verify. I would feel just as
comfortable buying a replacement from a company with a good reputation as
from the OEM. I would not consider purchasing a unit where even the
supply's polarity is in question or from a totally unknown supplier.

Of course, the ideal is not to "lose" the original PSU.