Hello all   I have put my ohmmeter across the output of the adaptor of a small pair of Logitech speakers. The adaptor has an output of 16 volts and 1.2 amps. The reading just moves about haphazardly.   Would this be something to do with the magnetic action of the transformer or am I not doing this properly?   More to the point, I wish to buy a replacement (as it is kaput) and I fancy a "universal" one. How important is the output and how far can I stray from the manufacturers requirement?