Ghost Issue

[old_coot88]

Originally Posted by Penthode

But I thought the last IF was eliminated by the fact the ghost did not change with changes to the fine tuning?

If the last IF is causing ringing/'ghosting', it does not change with the fine tuning.
Since VA561 has now subbed it a couple of times, that pretty well eliminates it.

[Penthode]

Originally Posted by old_coot88

If the last IF is causing ringing/'ghosting', it does not change with the fine tuning.
...

Alas, you are incorrect. If the last IF tube was indeed bad as suggested, the ringing would change with the fine tuning adjustment.

Since it had been suggested the last IF tube may be responsible, think for a moment the consequences in the change in the IF response which would result in the ringing or ghosting. A peak in the IF response would occur and when the fine tuning is changed, the video band would sweep the peak in the faulty IF response so that the frequency of the peak in the demodulated video band would change as a consequence. In other words, the ghost spacing would change as the fine tuning is adjusted.

If adjusting the fine tuning does not change the ringing spacing, then the problem must be after the second detector eg in the video amplifier. As has been pointed out, a badly terminated delay line would alter the baseband frequency response.

[DaveWM]

Did you try a direct injection of a composite signal at the 1st video amp? that should clear everything (tuner/IF/detector diode) before it. divide and conquer.

[old_coot88]

Originally Posted by Penthode

Alas, you are incorrect. If the last IF tube was indeed bad as suggested, the ringing would change with the fine tuning adjustment.

You may be right, and probably are. It's been a lotta years ago, and I don't recall noting whether it correlated to fine tuning.
Just curious, how many cases of last IF ringing have you actually encountered? I've seen it in 3 stage strips as well as the oddball two stage (6EH7, EJ7) strips).