[Milsurplus] BA Tune-Up Without B+?

[David Stinson]

Soon I'm going to need to tune the PA of a 
BC-669 transmitter.  If you've ever seen one, you know
this means opening covers, sticking your hand in where 
the B+ lives, fiddling with a bunch of slides and etc.,
and trying again about a dozen times per fixed frequency.
Each time you hope and pay you remembered to turn
off the B+.   Well, I'm old now and I will most certainly
forget sooner or later.  I've already played that game and
have the scars from it.  Don't think my weak old ticker 
will take many more jolts.

This is my idea- tell me if it will work:
Remove all power from the transmitter.  Jam the 
PTT relay closed.  Terminate the antenna connector
with a 50-ohm load.   (I know it's not designed for 
50-ohms.  I'll be using an external cap to fix that).
Feed a hefty on-freq signal to the PA grids.  
Put a scope across the 50-ohm load on the 
output.  Fiddle for max voltage across the load.
If I'm right, this will get the tuning pretty close and 
minimize fiddling with it and skip having an 
early estate sale.  

Should work even backwards- feed a 50-ohm terminated
signal genny into the antenna and put the scope on the tube 
grids.

What do you think?