I built the composite video injection and it is working, kind of. A few notes and questions.
- I pulled power from the 18v supply off the IF/video/audio pcb board. Normal (stock) operations it measures 17.5 volts. For the composite video injection circuit I included a 12 power regulator to get a regulated 12 volts. I was surprised to see the IF/video/audio pcb board voltage pulled down to 15 volts. Is there any reason I cant provide an external 12 volts to power the composite video circuit and avoid tapping into the "onboard" power?
- I grounded the circuit to "chassis" ground via a ground test pin on the IF/video/audio pcb board. If I use an external 12 volt supply are there any grounding concerns I should be aware of?
- I used a pot for now to temporarily adjust the video signal voltage. The normal video signal measures 7.5 volts and I was able to adjust the gain to match. I couldn't make full sense of my scope, I expected to see that same signal voltage but there was a difference. Am I just looking at noise, see below pics.
- The injected video required tweaking of the horizontal and vertical hold to get a stable picture but depending on the input (DVD vs converter box) the picture just didn't look right. Further I have (what I think is an unrelated) bad convergence problems which makes it difficult to gauge how well this composite video injection circuit is working. Any thoughts would be helpful, pending no changes suggested I may put it all back and dive in for some help with convergence.
Original video feed
Composite injection
