On Fri, 03 Jun 2005 11:47:44 +0100, P.R.Brady wrote:

Mike Atkinson {see sig for return address} wrote:

I discovered recently that the charger for my Black & Decker
drill/driver (HP9096) is now fubar. Now I've purchased a generic
mains adaptor that can supply sufficient current of the correct
voltage, but I don't know the correct polarity (positive or negative
'tip' according to the new adaptor's instructions). Does this
matter?

Try this:

Identify which wire is which on the old connector using the meter on
resistance range.

Connect the wire from the OUTER of the old connector to the outer of
the new charger connector using tape, a wooden clothes peg, etc
leaving the two 'inners' isolated and unconnected. Plug old
connector into the drill/charging base/battery and the new charger
into the mains.

Check voltage between the two inner connectors with the meter set to
a DC voltage range of about 30 volts. Reverse polarity of the new
supply and check voltage again. In one case you will get a high
reading of supply voltage PLUS battery voltage (for this 9.6v drill
expect about 20 volts) - this is the WRONG way round. In the other
you will get a lower reading (about 3 volts) being the difference.
This is the right way round.


Brilliant - thanks for such a useful reply. With the polarity the
correct way around, I do see approx. 3V. With the polarity reversed, I
actually get 0V, which I'm guessing is due to some internal protection
in the drill?

The upshot is that the supply *is* 'positive tip' (i.e. central contact
is positive), and this corresponds to the wire with a white stripe
running down it's length. This is in line with both Martin and Rusty's
posts.

My drill/driver is now charging (I hope!). Many thanks for all
responses.

Regards,
Mike

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