[Boatanchors] 51J4 Muting 12v PS?

[Revcom Electronics]

Gene,

Most ALL wallwarts will measure that way if they are NOT regulated,
and for the most they are not.
Some are and are usually marked as such.  They work on the assumption that
it is a constant, or near so load, and will be about the
voltage as marked when loaded.

Now some read a way low, in that case it is because they do not have
any filtering at all, just a transformer and a bridge recifier.  Common
VOMs will not reflect the RMS of the 120Hz ripple.  They depend
on the filtering in the unit they are powering.  It is all a matter of eco-
nomics for the manufacturer.

Put a load on it, 100ohms or so, and see what happens.  For a relay
don't worry about the initial voltage.

Rod
K0EQH
----- Original Message -----
From: "Eugene Hertz" <ehertz at tcaf.org>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, October 21, 2006 2:33 PM
Subject: [Boatanchors] 51J4 Muting 12v PS?


Hi All,

setting up my 51J4 to mute from my antenna changeover relay.  I was looking
thru my junk box for a 12V wall wart to power the 51J4 relay and found
something interesting that I can't explain...

Seems I have a bunch of these wallwarts that are labeled for 12VDC output. I
noticed that some output 12VDC such as an old laptop wallwart. However, some
others that are labeled as 12VDC actually output something like 20VDC when I
measure it with my dmm. One example is a wallwart for a cordless phone. It
is very small and the output says 12vdc 200ma.  It measures 20vdc on the
dmm.  Why would this be? I get the same result on a couple of these
wallwarts, so I don't think its a fluke.

Could it be because the wallwart is somehow expecting some loading? If I
loaded this would it output 12vdc? I am afraid to put 20vdc onto the 51J4
relay coil. Should I be afraid? Or if my theory of loading is correct, might
the output go down to 12v when connected to the relay? Just a little afraid
to try.

Thoughts?
Thanks
Eugene



_______________________________________________
Boatanchors mailing list
Boatanchors at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/boatanchors
** List Administrator - Duane Fischer, W8DBF/W9WZE **
** For Assistance: dfischer at usol.com **
$$ For vintage radio info, see the HCI web site $$
http://www.w9wze.org