"Arfa Daily" wrote in message
...

If it has got any external metal parts such as RCA (phono) connector
outers, BNC connector outers, 'D' connector surround etc, or possibly
screws for a stand, as these often go right through the plastic case,
and into the internal chassis, then try measuring from any such metal to
each of the DC power input connector's terminals in turn, using an ohm
meter. Chances are you'll find a direct connection, and that will be your
DC ground ( "-" ) connection. The other will then be the "+".

Arfa, you're usually dead-on, but this is quite incorrect. The side of the
connector that's "grounded" is not necessarily negative! A transistor radio
using PNP transistors would (presumably) have a positive ground, not
negative.


Assuming that it's a 'standard' co-axial DC connector, on most modern
equipment, 'pin' is "+" and side contact is "-" although that's not cast
in
stone.

No, it's not. I have Sony equipment where the pin is negative, not positive.


Rather than seeing which side of the power connector is grounded, I would
look to see which side of the electrolytic capacitors is grounded.