Gary, WB2UAQ --- the advice to make adjustments while the board(s) are enclosed is right on (seeing the solenoid coil on the VCO board helped me see why toroid inductor self shielding property is helpful!
I still could not measure any (filtered/smoothed) voltage at or above 0 (section 5.33 begins by having the tech adjust A19R3 or A19R9 - not sure why "or" - on the VCO board to get 0 volts at the detector test point.) It still isn't evident that this is caused by electrical problem in circuitry.
I decided to try experimentally the following -
Connect A2TP13 (A15TP6) to scope
Set frequency to 15.55 MHz (same as setting to 5.55 MHz, but didn't want to concern "out of range")
Set A19R3 (pretune) fully clockwise
Adjust A19R9 (detector) to see 50% duty cycle on scope
If A19R9 cannot reach 50% duty cycle (likely), adjust A19R3 slightly counter clockwise and repeat previous step
From this point
Watching scope, adjust frequency down towards 10.000 MHz, watching to see if duty cycle stays at least 20% from (0% or 100%) limit
Watching scope, adjust frequency up towards 19.999 MHz, watching to see if duty cycle stays at least 20% from (0% or 100%) limit
If either of the above exceeds limit (duty cycle gets close or to 0% or 100%), adjust A19R3 slightly counter clockwise, return to 15.55 MHz, adjust A19R9 back to 50% duty cycle, and repeat the previous 2 steps.
This may (well) be masking a problem I can't yet find, but seeing as at worst I get to try repair again, I'm going to put the unit back into it's (occasional) service.
(I do wish PLL unlock conditions were made visible without disassembly, but at least I know now to keep eye on frequency counter if anything is suspect...)
Thanks for everyone's suggestions and patience!
Dave
