Rca 721tcs

[Penthode]

All RCA TV's prior to 1952 used a split sound or non-intercarrier sound system. This means that the fine tuning is to be adjusted for best sound. Typically with these sets, the fine tuning is adjusted to the best sound much like any FM radio with a ratio detector or FM discriminator circuit. Typically as you adjust the fine tuning control from one end to the other, you will start with little or no sound, then weak sound through a null for best sound. As you continue turning the fine tuning knob, you will find a second null and then weak sound fading away as you reach the other end.

This means that the video and audio IF alignment can be a little tricky. The 721TS is a little simpler. But what you need to do is to adjust the local oscillator slug for best sound on the channel and then look at the picture.

Proper alignment tools are better than using the VA62 for this, but it can be done with a VA62 with a little understanding and care. Just remember to optimize the sound first with the tuner local oscillator then address the video IF. I suggest it is best not to touch the sound IF and discriminator and see if you can tune to get good sound first then check the picture.

I would like to add that RCA sets, especially the ones with four IF stages using the split sound design, although it is trickier to set up, will ultimately yield better pictures. This is because of the heavy sound attenuation at the at the video detector allowing wide bandwidth video with no sound patterning.