RF Signal Issue?
 

Just when I thought I was finished with the set on my bench I'm right back at it. I'm having what my gut is telling me is an RF signal issue. My problem is this, my picture is being washed out with what I can only describe as "bloated signal". My contrast control goes from zero picture (normal) to a normal but very dim picture (normal) for 1/100th of a turn and then get crazy washed out for a half a turn or so (not normal) then goes to the wonky picture that you get when the contrast control is adjusted too high (normal). If I disconnect the antenna input and just sort of lay the signal wire next to the antenna connections I get a normal range on my contrast adjustment again and my picture isn't showing the washed out symptom. I know the output I am using is ok as I have other sets running on that output with no problems. My gut is telling me there is a problem in the RF amplifier but space is CRAZY tight inside the tuner and I don't want to go messing around in that area willy nilly. I have swapped the 6J6 amplifier tube with the mixer 6J6 with no change in results. As I write this out I am thinking my next course of action is to check the supplied voltage and resistance specs against my set at the RF amplifier tube. Does anyone have any other suggestions? Any one seen anything like this before?

Odds are its an AGC problem, not the tuner. With the antenna unhooked
you have a weak signal. The AGC will tell the tuner & IF stages to
amplify at full. With the antenna on it should turn the tuner & IF
gain way down but isnt so you get overload. Start with the AGC
control. If not try the AGC tube. After that post all the info you
can, model, chassis etc & maybe pictures.

BTW some olds cheap sets didnt have AGC as we know it.

73 Zeno:smoke:

Make and model is an RCA 730ts. It does not have AGC, although that is a great suggestion.

I should have gone ahead with voltage and resistance measurements on the RF amplifier tube before posting here. It pointed directly to the problem (wiring error) and was easily remedied.

Glad I gave that caveat at the end !! Glad you got it going.

BTW sorry if I went too basic on you. Sometimes I cant tell the
"level". In fact I know almost nothing about pre late 50's sets......

73 Zeno:smoke:

did you check the contrast pot?