On Mar 5, 10:40*pm, Lady Veteran wrote:
john reves wrote:
I have a very small sony amplifier (the portable type such as you would
travel with and attach to an Ipod). I dont have the 9 Volt DC transformer
that came with it, so decided to use one of those 'variable voltage'
transformers that I bought from Lidl some time ago.

It's not clear from the transformer which of the polaritys the polarity
switch is indicating. So to check the polarity i used a voltmeter.

The choice of output voltages on this transformer is 3, 4.5, 6, 7.5, 9, and
12 volts. *The output I require for this particular amplifier is 9 volts.
But when taking a reading from the voltmeter it only reads 7.5 volts on the
9 volt setting.

Checking the others, 3volts is really 2.5volts, 4.5 is really 4, 6 is 5, 7.5
is 6.5 and 12 is 10v.

I read somewhere that a voltage reading from a voltmeter is different from
the reading taken when something is 'under- load'.

Would you use the 9 volt setting (which reads 7.5v) or use the 12v voltage
setting which reads 10volt, for use with this 9volt amplifier. *Thanks for
advice.

I would put it on 9 volts. Isn't that what the portable speakers take.
Don't always believe what your multimeter is telling you. You can your
multimeter on the pud pounder setting and probe Sitre Magana while he's
at the Post Office and it could tell you "not a probability."

But it would be wrong, wouldn't it?

LV

MMs are accurate on dc, and ac 50Hz sinewaves. Its only when you
depart from those that things /can/ get inaccurate. There is one other
known cause: a low quality digital meter with a dying battery, some
can read low.


NT