After changing the EPROM to the modified version again the Programmable 30-50MHz IF does allow setting the frequency below 30MHz. However I noticed that the frequency is off somewhat and drifts.
I watched a video where Bob Andersen uses a modified EPROM and if you look closely at the frequency on the scope, it does seem off a bit.
https://www.youtube.com/watch?v=Y6WOjtaBqLM
The video was made nine years ago with an earlier version from Zenith6S321. Bob didn't seem to notice the frequency discrepancy.
I noticed that all the documentation I could find concerned the VA62 like Bob and I have while Zenith6S321 unit is a VA62A. Maybe there is some important difference.
I'll add a link to an earlier thread about the modification kit for the VA62.
http://videokarma.org/showthread.php?t=273989
Zenith6S321 has not been active on this forum since 2018.
I recently took the liberty to upload the info on the kit CDROM to the BAMA site.
https://bama.edebris.com/manuals/sencore/va62/
To paraphrase Jimmy Durante, "Good night to all of ya, and good night to Mr. Zenith6S321, where ever you are."
https://www.youtube.com/watch?v=EWN97q7xtDE