http://mirror2.ipdb.org/files/1476/Bally_1977_Lost_World_Manual.pdf Is a manual. This will be very important. You are having solenoid board issues or connection issues. This is the board at the top right.
Check the fuses on the rectifier board (on right side of cabinet) especially F4. Check this fuse! There is also a fuse under the playfield near the wiring for the flippers. Check this fuse as well.
Check voltages on rectifier board on the test points (Put black probe on the ground braid strap on bottom of backbox and red on the test points with meter on DC Volts, Test point 4 is AC, but most are DC).
I have attached pictures from the manual that show the connectors from the solenoid board that you are having problems with, and the test points and the voltages you are looking for at the rectifier board.
If you look at Connector J5 on the solenoid board pin #14 is the right slingshot (bouncy thing by the flipper). The numbers on the schematics should be right, but notice that they are not in order. They are numbered on the schematics as they are on the board. It looks like you are missing a bunch of these solenoids, as well as out hole which is on connector J1 so I would suspect a fuse or connection of some sort. This could be the connector the guy was talking about.
If you read the manual you will see how to enter the diagnostics by using the buttons on the inside of the coin door. See page 13 of the manual. Basically you push the button once and the lamps blink on and off. Press it again and the displays display numbers, press it a 3rd time and the solenoid coils should fire and the displays should count which coils are firing. This is the solenoid test.
Report back with your findings!
edited to change F1 fuse to F4. I was tired last night.
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