How do we wake up this old Mac?

We bought a plotter machine that cuts vinyl or makes one-color drawings, and the computer that came with it to drive it is an old G-series Mac. We’d like to use another computer, but we can’t find the Roland plugin for Illustrator online, so for now we have to use this. It has a big monitor with a weird power button that pushes in slightly but is not separate from the monitor case in the usual sense: http://www.adrive.com/public/9GJEGh/Mac%20monitor.jpg. The button is glowing in the lower right.

When the computer goes to sleep, pushing the button makes the light brighter, but the computer does not wake up. Tapping the power button on the tower does nothing. All we’ve ever been able to do is hold down the tower’s power button until the computer turns off. What trick are we missing here?

Bang on the keyboard? That’s the usual way of waking things up.

Just hit a key on the keyboard.

The monitor may have the defect that it won’t wake up once it goes to sleep mode.

You might press some keys, or anything required to wake up the tower, AND THEN turn the monitor off and on again, at the mains (or remove the mains power cable) to see if it comes good from the power cycle.

Hitting keys doesn’t work, or jiggling the mouse. The power cable for the monitor goes to some funky plug on the back of the tower, where I guess it’s getting data and power both, and is a pain enough that I’d rather just hit the reset button.

You will eventually corrupt your hard drive if you keep force-restarting your computer.
You can set the machine not to go to sleep, or to just set it to only put the monitor to sleep.

When the machine is asleep, the power button on the tower itself (and the monitor, too, I think) will “throb” (snore). If it doesn’t, the machine isn’t asleep.