ARE LATE 40s/EARLY 50s RCAs PRONE TO LOW VOLUME ISSUES?

[Penthode]

Hi,

I have been following this thread for the past few years after being directed to it from a fellow member. I have a particular interest in the earlier RCAs having worked on a number of split sound sets over the years. I have been a professional broadcast engineer for about the last 30 years and a faithful 8T243 has been my friend for 42 years.

I have no trouble with audio level on any of the split sound RCA sets. I have also never had to replace the mica capacitors in the RCAs as they have always appeared to have been of the best quality. (That has been my experience to date). And because the audio is FM, broadcasters reducing the carrier level slightly will not affect volume since it is the frequency deviation and not the amplitude which affects loudness.

What I have found more critical in these sets is IF alignment. The best test for audio alignment is to just tune in a TV signal. Fine tuning on these sets aim for best sound. As you tune for best sound, you must tune through a null. The process is this: tune towards best sound through a null, the sound is then loudest and clearest and as you continue tuning, you will reach another nulll and the sound will then be weaker and diminish in quality. You must tune between the two nulls and the level will be weaker either side of the nulls and best and loudest between the nulls.

If your split sound set does not tune in this way then I would suspect the "phantom tweaker" has been at your set in the past and has meddled with the alignment. You can still get a bit of audio when misaligned but it will always be weak and not clear.

The last thing which must be mentioned is that the Video IF and Sound IF alignment is linked together and generally a set should have video and audio alignment done together. This is because you have to ensure that the best picture cooincides with the best sound. On the RCAs, the better sets all have four IF stages and a 4 MHz bandwidh and so should provide an excellent picture and sound when properly aligned. It is essential that the video carrier is at the 50% point on the IF response when the the sound system is properly aligned and tuned.

Please be assured that my 8T243 is plenty loud when properly aligned!

I wish you the best success with your set.

Terry