[sf-lug] AC adapter compatibility

Michael Paoli Michael.Paoli at cal.berkeley.edu
Wed Feb 25 04:11:14 PST 2015

And alternatively/suplementally:

Very close careful visual inspection of power supply (notably labeling)
and laptop (labeling and around power jack) may also indicate polarity.
And, back to the guessing/praying, with a bit of luck, if such labeling
is found, it may even be labeled correctly (usually so, but not always).
Also, if one has access to the suitable test equipment (or to someone
who does and can put it to use), if one still has known good supply,
the polarity of the power supply output can be rather easily tested.
If one only has the laptop, there isn't a 100% sure-fire dead simple
way to safely and explicitly test the polarity of its power input
jack.  Also, as to polarity on plug/jack, do *not* rely upon color
indications, but look explicity for the + and - signs, and indications
as to which is center and outside of the plug/jack.  (Typical
convention is to often use black for - and red for +, but also
not that uncommonly the reverse may be the case, e.g. black for
common, and red for "hot", which may be +, or -, relative to black;
and don't even start to think you can extend that to AC, or you might
kill someone).

Also, another caution on physical connector - you want to be sure it's
correct match, and not just "merely seems to fit".  E.g. if the
Outside Diameter (OD) matches, but the Inside Diameter (ID) doesn't
match, but physically fits, this can result in hazardous/dangerous
overheating.  Likewise if there's mismatch on length.

> From: "Rick Moen" <rick at linuxmafia.com>
> Subject: Re: [sf-lug] AC adapter compatibility
> Date: Tue, 24 Feb 2015 22:07:53 -0800

> Quoting Michael Paoli (Michael.Paoli at cal.berkeley.edu):
>> And, back to the list, as I'm presuming that's where this was intended
>> to go to.  And yes, you make good point about the acual barrel plug or
>> whatever the connector is.
> Two alternatives to guessing and then praying that a new plug has
> correct polarity, etc.:
> Call vendor.  Describe problem.  Follow advice offered.
> Or:
> Determine yr. underlying OEM model.  Using said data, Web-search AC
> adapters (esp. in usual places, e.g., Ebay).  Order one.  Celebrate.
> (Beaucoup online vendors stock aftermarket AC adapters, Li-ion packs, &
> such all.  They list what's compatible with what.)

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