I should add that the self test button on the coin door demonstrates that all lights work, except the playfield "Extra Ball" light. Even the BACK BOX "Shoot Again" lights up (Q3 leading to pin 21 on J2) so I don't need to verify it. What is interesting is that I cannot identify a "shoot again" light in the Mata Hari playfield although I clearly see it identified as Q40 (leading to pin 22 on J3 in the wiring schematic (thanks Billc479 for pointing this out)). The one I had been referring to earlier that "has no voltage" is Q26 which leads to pin 7 on J2 (labeled " AB Value X Ball"). To check that voltage, while in self test mode, I checked each of the playfield lights in the "Making A & B Game Scores" row by simply touching the positive and negative for each lamp base. Each had adequate voltage except the playfield light for "Extra Ball" which had no voltage and of course it is the only thing that doesn't come on with the self test (and still don't know where the playfield "shoot again" light is even located).
I have not tried to manually make A&B lanes reach the extra ball requirement but I have reached the total score requirement for extra balls while playing and no extra balls came. I certainly will try the manual approach for AB.
Hope that clarifies my dilemma.