In article ,
"DIY" writes:
I bought a couple of wind-up dynamo LED lanterns in anticipation of the
winter power cuts. They have a 6volt charging socket but there is no
indication of the polarity on the case next to the socket and no
instructions as to polarity. My understanding is that the usual convention
is that the central pin is positive and the outer sleeve is negative on the
charging plug. Is this likely to be correct?

An adaptor was not included but I have got a regulated DC adaptor that can
be set from 1.5 to 12volts with either a positive or negative tip.

+ve centre is most common, but not universal.
You might find that you can measure a polarity on the socket
with a test meter, but it might not handle being shorted out
without damage.

Another issue is if the socket is meant for a power supply
or a charger, and this will depend if the unit contains its
own charging circuit.

Without any details being provided, you are probably going
to have to open it up to be sure what's inside, and if it
needs a charger, what type and capacity battery it has.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]