Hey Albertapinball, welcome! That looks like a fun game. I've got a Bally from '68 too. I'm going through your post bit by bit trying to dissect exactly what your problems might be, but before anything else, if you haven't done so already, read this from top to bottom. Between that site and your own eyes and ears, you'll have all the answers you need.

This is normal, or maybe you should expect to hear the light hum of the transformer. Just plugging it in shouldn't make anything else happen. If you press the left flipper button at that point, the lights should come on but nothing else should happen.

Is there anything else that happens? Does the score motor stop running or just run continuously?

Now we're getting into the weeds. No idea about this, but I've seen similar problems that are the result of dirty or shorted-out jones plugs. Clean and re-seat all of these, and make sure there are no screws, nails, or anything else shorting the connections out.

That's probably not everything but hopefully that gives you a good start. Let us know how it goes.

The best way to clean the jones plugs is with a wire brush.

After that, I would look over every single switch on your playfield. Check to see that all of the switches are gapped properly and not making contact when they shouldn't. Start with the outhole switch.

^^ You have a bell missing and a coil. Check your schematic for the coil application and for the coil/bell you can get them from Pinball resource.

Pbr has those too,best change them instead of trying to salvage the old ones as they were cheap/junk when Bally made them.

Do you have windows? If so ,use control(Ctrl)Key and the +/= key (zoom in)or with the -/_ key (zoom out)simultaneously to adjust the size and it looks fine to me. Link> http://mirror2.ipdb.org/files/1606/MiniZagSchematic.jpg
As far as the coil wires go, 2 orange go on one tab and the white /red tracer go on the other one.
The black and the other orange on the m&b not sure? As my 1965 bally does not have the switching.
Maybe someone can chime in on the proper wire layout.

What coil is that? And is it supposed to have three lugs? I would expect it to only need 2...

Also in terms of loose wires, in your picture I see a white/orange, two oranges twisted together, a dirty orange coming off the EOS switch below/left of the coil, and a black coming off the same switch. The white/orange attaches one lug of the coil, I'm pretty sure (that's how it is in my Dogies), the two oranges together attach to the other lug, and I don't know what those other two are for. Consult a schematic! If you don't know where to look, scan it and post it here and maybe somebody can help you.

I know it's been a little while and I'm not sure if you've solved your problem, but I've recently started refurbing a friends unit. There are in fact 3 terminals on the coil('68 version). Starting from the backglass heading back to the rear most of the machine, you should have 2 orange leads, plus a red lead(which goes to the EOS switch just below); the middle terminal should have the black return lead from the same EOS switch; and the furthest back(closest to you) terminal should have the white w/ orange by itself.

Also, I'm having trouble with the ball counter. The game seems to play perfectly otherwise, but when the ball drains it just pops it over for another round but doesn't increment the ball counter wheel, such that you can play indefinately. Also, the ball counter never resets when you start a game. Anybody have this problem? I've cleaned just about every contact point, so I'm not sure what's going on.
Thanks!