Quote:
Originally Posted by Penthode
The effectiveness of the Leader is how close the Leader output is to the channel carrier frequencies. Let us assume it is close.
What channel are you using with the Leader? Have you tried other channels?
Stepping back, let's reason this out. It cannot be a tube socket in the tuner because the tuner carries both video and audio. However the video is broadband and the audio is extremely narrow bandwidth which is why you may see video but hear no audio if the tuning (local oscillator) is slightly off.
You have exchanged the oscillator tube with other 6J6's? (The oscillator 6J6 is the one closest to the front of the chassis. The other two do not matter). You have the proper tube shield fitted? (If the shield is missing, the tuning will be off).
The audio video split is immediately after the tuner. You have monkied with the alignment so that remains an unknown. Have you confirmed there is plate and screen voltages on the IF stages?
Here is another gotcha on RCA sets: Is the discriminator tube lit? There is a 5.1 ohm resistor in the 6AL5 filament path that carries a fair bit of current and often opens. It is inserted in the path to allegedly improve the discriminator linearity hence fidelity. Check to see if the 6AL5 is actually lit and if not you can simply bridge the 5.1 ohm resistor if it is open.
Next, are you familiar with analog TV receiver fine tuning where you do not tune for brightest picture but for most detail? This is because analog TV used vestigial sideband transmission and the video carrier must be tuned off to one side of the the video band to 50% up the slope of the video bandpass on one side. That is the point you will ind the sound. If the picture is a bit smeary and lacking detail, that is a sure sign the fine tuning is off and why you may not have sound.
To recap, tell us what channel you are using, ensure the 6AL5 is indeed lit and see if the fine tuning has sufficient range to lose the video when you adjust to the end stop of the fine tuning control. (On the lower VHF channels, because split sound sets have a narrow tuning range, you may not see much difference. But try it and see).
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The discriminator is lit, in fact, it's a NOS tube.
I've tried both channels 3 and 4 with the Leader input and turned the fine tuning through the full range for both. I also scrolled through the other channels in case something could be heard.
I changed the oscillator tube multiple times with different 6J6s. I have the shield in fact, this chassis has an inner steel shield and an outer lead shield over the tuner oscillator that I put back in place with every tube I tried.
I have ohmed out the discriminator resistor and it is fine. I can go back and recheck this evening. It's an odd looking resistor as it almost looks like ceramic.