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 Post subject: voltage drop: coping or bad?
 Post Posted: Sun Aug 15, 2010 12:20 pm 
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Joined: Sat Jun 30, 2007 10:36 am
Posts: 208
My new replacement OEM power adapter gives lower output voltage sometimes. My laptop said it was delivering 70 rather than 90VDC, the message appearing to come from the laptop's hardware, not the OS. Once was a couple of weeks or so into using the adapter on and off. A couple of times one day were after mildly bumping the brick. I doubt it was a problem with the building's AC power; I did not notice changes in my ceiling fluorescent light or my AM radio. The brick's DC connection was already firm, at least the first time. My laptop any-key bypass resulted in the screen display going off-center and stretching horizontally more than vertically, including the pointer, and the Linux Gnome panel (Fedora 10) not responding to mouse-clicking. Alt-tab worked and I still saved in my word processor but couldn't activate another browser tab. I quit programs. Either warm-rebooting or going to the CLI terminal (ctrl-alt-F2), logging into the GUI's current account, and going to the GUI (ctrl-alt-F1) cleared it up.

I think I have nothing to worry about, just a procedural annoyance, and it hasn't happened in a little while -- or do voltage dips in an adapter signify something much worse?

Thanks.


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 Post subject: Re: voltage drop: coping or bad?
 Post Posted: Sun Aug 15, 2010 12:29 pm 
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Joined: Sun Feb 04, 2007 11:44 am
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Quote:
My new replacement OEM power adapter gives lower output voltage sometimes. My laptop said it was delivering 70 rather than 90VDC, the message appearing to come from the laptop's hardware, not the OS.

You mean power, not voltage, as in 70W vs. 90W. If it is truly a 90W adapter, it sounds like it may be failing. In that case replace it with another 90W (or higher output) adapter. Scott.


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 Post subject: Re: voltage drop: coping or bad?
 Post Posted: Sun Aug 15, 2010 5:35 pm 
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Joined: Sat Jun 30, 2007 10:36 am
Posts: 208
A giant OOPS because I should have thought of that.

But it sounds like at worst it's only a problem of failing to deliver adequate power, so I can wait it out and see if it deteriorates further, since I have a battery for orderly shutdown.

On wattage vs. voltage, I'd like to revisit the laptop's screen message to see if I misread it (I guess I must have unless it gave the wrong unit, too) but I don't know how to retrieve it. It's probably in the hardware. And I don't know how to induce the brick to give too little power without risking doing it permanently. But the Dell specs say 90W and 20V output and so this replacement should be 90W/20VDC also, not 90 or 70V.

There's a hint online, but only a hint, that the OEM manufacturer may be making the same model for both wattage outputs, perhaps using an internal switch or wiring pattern I can't see, but set or made according to which laptop it's made for. That might suggest what kind of defective operation occurred with a mild bump. Mild bumps since then have not had a noticeable effect.

Thank you, especially for catching my likely blooper.


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 Post subject: Re: voltage drop: coping or bad?
 Post Posted: Sun Oct 24, 2010 2:14 pm 
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Joined: Sat Jun 30, 2007 10:36 am
Posts: 208
Confirming my error that Scott caught and also reporting a problem's possible cause:

The reduced power output occurred today, and this time I copied the displayed message, which is formatted like other internal hardware-level pre-OS laptop messages:

WARNING: 70 Watt (20V, 3.5A) AC adapter detected. System will not be capable of running in full performance mode without a 90 Watt (20V, 4.5A) AC adapter.

Press any key to continue in battery optimized mode.

My error was in misremembering the earlier message as being about 70 volts when it's about 70 watts.

But I may also have found a cause for the lower wattage, although this is more speculative. For a long time, maybe a couple of months, during usually daily use, the lower-output problem didn't recur, even though I traveled with the adapter and used it home and elsewhere.

At home, I usually let the adapter rest on its end, hanging from the laptop cable and resting on the power cable, possibly pushing the power connector more firmly in, although it already feels firmly in whenever I check. This position is about 20 degrees from vertical, with the output end up and the LED usually visible. Used this way, it has not been producing the lower-output message. The other day, I repositioned it to rest horizontally. Shortly after that, not the first time but soon, the lower-output message appeared and could be made to appear more than once by unplugging and replugging the laptop connector. Restoring the the familiar semi-hanging position of resting on the power connector put an end to the lower-output message when I rebooted.

What confounds this analysis is that when I use this elsewhere the power supply is probably horizontal, either LED side up or resting on a long edge, with no problem. Or, if that's not confounding, that could mean that the problem occurs intermittently for horizontal positions but is solved for the hang-and-rest near-vertical position.

Reattaching a foot with GE brand silicone glue, which seems to have worked, given its timing, is unlikely to have affected this problem. No glue spilled anywhere near the adapter.


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