Injecting video in DuMont RA-102?

[Phil Nelson]

Progress! I replaced R23 with a 56K resistor and replaced the .002 coupling cap with an .01 cap. The picture was nice but the vertical was still somewhat unstable. I doubled the value of the coupling cap to .02 and now the vertical is very stable.

Here's the video signal direct from the generator:



Here's the signal coming out of the preamp/inverter:



And here's a DVD using the preamp/inverter:



The screen image is so strong and bright that I had to turn it way down to avoid washing out in the photo.

I tried using a 9V battery in place of 12V, and it seems to work fine with 9V.

It would be nice to use this in a switchable A/V adapter like the one described in http://antiqueradio.org/A-V_AdapterForVintageTVs.htm . Then you can just flip a switch to change from A/V input to ordinary input from the antenna. Changing the value of R23 complicates that scheme, but I suppose there's a way.

If I installed this permanently in the chassis (with or without switching), it would be nice to find (or generate) a +9V source somewhere in the chassis rather than rely on a battery.

Phil Nelson

[old_coot88]

Phil said:

If I installed this permanently in the chassis (with or without switching), it would be nice to find (or generate) a +9V source somewhere in the chassis rather than rely on a battery.

You could rectify it right offa the 6.3V heater supply using a single diode and a filter cap. That's assuming one side of the supply is grounded. It would give you real close to 9V DC.