Re: Cossor 1039 Oscilloscope
The waveforms are as I would expect after building a very basic scope myself. You have to have the X sawtooth osc running generally slightly slower buy a division of the incoming Y waveform frequency, this gives the sync circuit a chance to trigger the sawtooth and lock at the same, either rising or falling voltage on the incoming waveform. Clear as mud I know, was never very good at descriptions.
The velocity control is doing varying the speed or repetition rate of the sawtooth, the synch triggers it at some amplitude of the Y voltage. Think it is covered to a degree in Foundations of wireless 8th ed, on Time bases page 421.
The non linearity of the waveform I believe can be caused by the fact that the deflection plates are not being symmetrically driven, in that one plates is not decreasing in voltage as the other increases as you would get by see-saw driving of the plates.
If you look at the spec sheet for the DH7-91 there are different tolerances for deflection distortion for the two systems with asynchronous being higher. In fact of you check the specs they will only quote for 72% of the useful scan area as you get closer to the edges of the crt the distortion will get worse.
Adrian
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