Sir David . . . . .
Well, the first thing that you learned was that a mere 1V p/p audio output from of the VCR's audio output is NOT going to punch "speaker" sound thru an unpowered, dormant " 64 RCA ".
Now I knew that the VCR had its own isolated switch mode power supply, but was uncertain of any potentially adjunct hummmmmmmm from ground loops, thereby the utilization of series isolation capacitors on both, the shell and center pin of the end of the RCA patch cable
Now let me know of any objectionable hum of the VCR audio coming out of the RCA speaker, or is it at least tolerable ?
See if the volume control range will let you have all of the volume and sound quality required.
With our next consideration, after your just now having confirmed that the power supply and all of the audio amp string is amplifying audio, lets probe the sets RF portion.
That is, initially considering that audio from the RCA set is clean enough.
To start, since your FM and AM are apparently BOTH inoperative, consult the extreme corner left of your supplied schematic and note that the top portion is the FM portion and it is receiving its switched power supply input from the BLACK BOX 6 reference , at two FM positions.
DC meter those voltages presences, while the radio is in either of its two FM positiions.
Then, MOVE the knob to its sole AM position and confirm that the prior FM voltage drops off.
Move down the schema to the bottom left corner and then note that the AM radio portion there
is receiving its power in thru the BLACK BOX 7 reference .
Confirm presence of that AM voltage only when the mode switch is placed out of either of the sets two FM positions.
Standing by for your tests results . . .
73's de Edd