I have the opportunity to purchase an o scope the owner says that it powers on and a dot moves across the screen. Does that indicate that the unit will work?

 

No.

I bought a second hand scope that the second channel read off the wrong voltage.

You need to try all channels with a signal generator.

 

Thanx Nigel

 

If a dot is moving across the screen, then that indicates that the horizontal amplifier is working at low frequencies. At high frequencies - the dot should look like a straight line.

You can check if the vertical amplifier is working by placing your finger on the probe tip and looking for a messy sine wave at about 16.6ms (60Hz).

You can't really check calibration unless you have a waveform generator that's calibrated.

 

many scopes have a square wave generator available on the front panel for calibrating probes. Just connect a probe to it and you should see a square wave on the screen. You'll have to play with the controls a bit to see the wave.