Injecting video in DuMont RA-102?

[Phil Nelson]

Originally Posted by old_tv_nut

The 4.7 is 4.7 microfarads, right? The + side should be connected to the transistor base.
You are going into pin 4 (grid) of V4 (6AC7), right? Did you disconnect the detector diode?

Yes to all questions. 4.7 mfd electrolytic with + going to base.

Originally Posted by old_tv_nut

Since 5.6 k is close to your collector load, it will reduce the AC gain, so disconnect it and replace it with something like 56k.

There is no 5.6K resistor in the schematic supplied by vts1134. Do you mean R23 in the RA-102 schematic, the 5.6K connected to pin 4 of the 6AC7?

Thanks much for the various suggestions. I will tinker some more and report back (possibly tomorrow).

Phil Nelson