Hi uncle_jose
we can lift the playfield - 15 degrees, 30, 45, 60 degrees and use the wooden stick or metal stick to hold the playfield in this position.
We can lift further 75, 90, 115 degrees - pull the playfield a bit against the player and lean-on the playfield onto the Backbox. Not very stable - may want to secure it. Maybe a bit better access to "relays mounted on a relay-bank" ?
The FIRST thing I do when I look for a fault: I toggle-off the pin and unplug the main power cord (Safety Reasons). From schematics and manual I take the information "Switch-XYZ on Relay-QQ" and the color of the involved wires are "whatever-one" and "whatever-two".
I locate in the pin the relay and the switch --- I grab the wire in question and gently pull a bit - question: Soldered-on or broken-off ?
Maybe one of the involved stuff sits in the Backbox and another goody is mounted on the Mech. Panel in the Cabinet: I also check the Jones-Plugs (wires soldered-on or broken-off ?).
I dislike to work on "Switches in Relays sitting in a Relay-Bank" --- I dislike to work on "Switches on the Score-Motor". So sometimes I am rude to the pin --- I cut a wire a couple of inches away from the Solder-Lug. I take a cigarette-lighter and burn away the insulation fabric. Now I have a place to mount an Jumper-Wire for testing. See the JPG - "red line jumpering testing the single-bonus feature".
When the Single-Bonus-Feature works: Fault must be in "what I have jumpered".
When the Single-Bonus-Feature still does not work: Fault must be in Score-Motor-Switch or other connecting wires.
K-Mart and such stores - automotive departement - car-electrics --- they sell single male and female plugs - we can attach the wire by squeezing the housing of the plug --- very practical.
And when I have finished testing: I plug together the cut wire and have these K-Mart-plugs in my pin forever ... Greetings Rolf