"William Sommerwerck" wrote in message
. ..
"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.


I think you'll find that on 'most' modern - and I did say "modern" in my
original reply - equipment, this has been pretty much standardised such that
DC "-" *is* common ground. Sony kit that I have seen in recent years has all
obeyed this 'convention', so I'm willing to bet that any Sony items that
follow the opposite 'convention', are not "modern". Pin = "-" used to be the
'convention', but for all mainstream manufacturers whose equipment I work
on, this has not been the case for many years. It was only usually the
Japanese manufacturers that followed this anyway, as I recall.

As for a transistor radio that uses PNP transistors, I haven't seen one that
uses transistors at all for many years, let alone PNP ones, so I think you
might be struggling to fit that into my "modern" category, also.




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.


This is, of course, the very best way, if the owner wants the trouble of
taking it all to bits, and identifying a suitable electrolytic to use as his
reference. However, I would put my name on the line that the method I quoted
before, would 99.5% yield the same result, with any 'modern' item using a
coaxial DC socket. Perhaps someone out there with a Gateway monitor could
confirm which way round it is, then neither of us will be applying guesswork
to experience and coming up with sage advice ... d;~}

Arfa