My CTC-16XL Project.

[Yamamaya42]

Originally Posted by Tom9589

Does anyone know why the second IF stage is "floated" above ground by about 150V? Is it an effort for using the second IF stage as a voltage drop to provide plate voltage for the first IF stage? Kind of like the audio output tube circuit in some B&W sets to provide an approx 140 volts source at its cathode. I see where RCA used this arrangement for many different models.

If the AGC were way off, the second IF could be biased such that the voltages for both the first and second IF could be way off. Go back and check the voltages on the first IF stage as well. There is a good chance they are off as well.

I only saw about 20-30v on pin 5&6 of the 1st IF ( should have been 160v) and nothing on 1,2,7 (less than 1v) , and so I look at the 2nd IF , and saw it had the plate voltage, but everything related to the cathode's flothed ground was very low. (30v)
even with 1st IF removed the cathode voltage was gone.

I can see WHAT is happening, but since I was probing with tube test sockets, it don't know why yet.

with 1st IF removed, should i not see 160v ( approx) on the cathode of the 2nd?
I'm just going to have to make time at some date to take it all apart and check all resistors / caps in the area again.