No wall power?
Loose power cord?
Loose wires in the power box?
Blown thermistor or fuse in power box?

So basically, start at the beginning from the wall to the game and onwards to the pc boards.

+1 all of these

especially the fuse in the power box. happened to me once and it was the last thing I checked lol

First, make sure 110 volt AC is getting to the Line Filter that will rule out your line cord, Outlet Etc. Make sure the voltage is getting through the Line Filter then trace the wires to the power switch and to the Transformer board. Once that's verified let us know if the game still does not turn on. I have had switches go bad I have also had line filters go bad in an open state. The varistor across the Line Filter would not cause the problem you're having you can remove it and the game will still work but you won't have protection from surges such as when a bowling alley turns 50 upsetting mechanisms on or off.. If the varistor were shorted, you would immediately blow a fuse/circuit breaker when you plug the game into an outlet. I mean the fuse / circuit breaker in your home electric panel.

Does your game have a service out let in it ? If so plug a lamp or something into that.

If that works, you have power into the game so then the main fuse and line filter etc. are working.

LTG : )

Check the wall voltage first.

Then check fuse f6 with the ohm meter to see if its good. If it's bad, this is the problem starting place.

Check the voltage at the line cord/filter/varister (little silver box with the red disc thing on it) with the game plugged in.

And check voltage at the switch, they go bad too.

Red disk thing is the varister, little silver box is the line filter.

Basically see if you got power to the game.

Simplest test! Good idea.

How is the fuse f6?

Pull it out test with ohmmeter.

Check voltage at f6 if none then the problem is before it.

Check voltage at the switch in case its broken.

Check the connectors to the transformer board and transformer itself for burned connections or loose wires with game turned off.

Post pics if the transformer board , someone might see something.

Your DMM is probably ok for this.
Set it to 250v

If no power at f6 then probably the transformer board needs work or bad/burnt connectors

Check your voltage at test points

Fuse holders look really crusty and corroded.

With game off. Clean the holder for f6 and the other fuses.

Maybe it's not making contact, it's pretty bad.

You might also plug and unplug the connectors on the transformer board one by one to freshen them up.

And check for melted or loose or broken off wires.

Is pin 1 on the right(upper right) connector fully seated in the wafer block?

Yeah, the connector pin has two crimp points, one is supposed to crimp onto the wire, the other is supposed to crimp onto the insulation. You dont want to be pulling on the wire when moving things around, it's much better to be pulling on the insulation.

I have used a Dremel 443-02 dipped in Isopropyl and cleaned them in place.

I've used dremel bits in my drill, shouldn't be a problem.

I've had two on-off switches fail on Bally early Solid State pins when I worked on a route. Verify with a meter or jumper wire.

ever consider the on/off switch?
while your waiting in a volt meter, try jumping the lugs on main the switch.
rare but they can go bad.