HELP with repair RCA TK-76

[6GH8cowboy]

I am the proud owner of a TK 76 and have fired it up a couple times a year. Performance has been good and registration near perfect. Last year the viewfinder CRT fillament went bad due to a shorted cap in series. Then the VF viewfinder Vert sweep failed. This year when I fired it up W/O the viewfinder. The Pix is VERY dim and soft looking (like a bad vidicon in a CCTV camera). Is it possible all three plumicons are bad at the same time?, probably not but thats thats what this forum's about. Power supply volts at the P.S. pcb are right on but without a schematic I can't go much further.
I suspect the VF vertical problem is a bad chip on the front main PCB and the dim/ soft pictures a voltage missing there as well.
It's always my intention for my technical antiques to be functional as it adds to the joy of display and demonstrating. Help me keep this one alive a bit longer

Dave