Testbeeld generator voor zelfbouw

Kevin Pye G4EER

The original article for the ZNA234 Test Pattern and Sync Generator
was published in the BATC book 'Micro and TV Projects and
the circuit was as shown below ( Fig.1. )

When I came to use the mixed sync output from the unit
I found that the video waveform was also present.
I added a diode D1 to isolate Mixed Syncs from the video.
but this upset the DC conditions for TR2 so RA was added to
compensate then adjusted the bias of TR1 to give the correct 70:30
Video:Sync ratio The modifications are shown in Fig.2