[sf-lug] AC adapter compatibility

Christian Einfeldt einfeldt at gmail.com
Wed Feb 25 12:21:30 PST 2015

Thanks to everyone who replied to this thread!

On Wed, Feb 25, 2015 at 4:11 AM, Michael Paoli <
Michael.Paoli at cal.berkeley.edu> wrote:

> 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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Christian Einfeldt
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