After trying several tuners, testing/replacing every component and doing multiple alignments it finally occurred to me to try different RF sources.
Our local LP OTA channel 6 pseudo station comes booming in, but I know their audio carrier is much stronger than normal.
My trusty OTA ATSC converter box I use with all my sets has solid video but weak audio.
Next, I took the composite output of the converter box and fed it to a cheap stand-alone RF modulator. That definitely improved the audio
It's also much better if I use a Blonder Tounger modulator.
So I'm concluding that it's working as designed and it's just more sensitive to the audio carrier than other sets.
I had so much fun with this set, I decided to plunge right into restoring another one
Electrically anyway. I figure that will allow me to compare the performance of the two. It should also go a whole lot faster since it's fresh in my mind.
I already have the lower chassis rebuilt and it seems to work fine.
However, I noticed a blue flash over in the 5U4 on power up. I tried a few different 5U4G and 5U4GB and all had flashover too and with both power supplies.
The original design has a 40uf + 2Hy choke + 40uf for a filter. I replaced them with 47uf. I wonder could that be putting too much of a strain on the 5U4 ? Perhaps I should knock the 1st cap down to a 33uf ?
Or maybe throw a power resistor or thermistor in series
