trm wrote:


If you don't have a scope there's a great way to check for ripple on supply
rails. All you need is a reasonably sensitive audio amp, a set of cheap PC
amplified speakers might do, attach a croc clip to the ground and a probe to
the audio input (preferably coupled via a capacitor, though there should be
one in the amp itself) and you have a way of listening for any hum!
Attached across the smoothing cap of a power supply it should give a good
indication whether the cap is doing its job. This should be done with a
reasonable load on the power supply.

It's crude but it worked well enough for me before I could afford a scope.
Obviously it should not be used on high voltage sections for safety reasons.

Dave


One of my most useful items of test gear has resided in my toolbox for
over 30 years, I made it myself back in the 70`s. It`s a crystal
earpiece with a croc clip on one lead and on the other lead a probe made
from an old Biro with a capacitor in series with a sharp point. You can
use it to listen for audio signals from phono levels right up to
loudspeaker levels, trace for distortion and check rails for hum and
fizzle etc, or as a simple input device for testing audio stages (you
blow into it)

Ron (UK)

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