Whatdunnit to Whodunnit?

[MisterMarty]

So, there's an audible clicking on sound when it's powered up but there's nothing else happening. No lights, no sounds. Your suggestions for how to set about putting it right would be greatly appreciated. Before you ask, I've already tried washing down the interior with domestos

 

[pinballmania]

CPU not running ? Reseat connector below short grey ribbon cable on driver board to start with. Then try reseatting ribbon cables and push home the square socketed chip on the CPU.

 

[MisterMarty]

CPU not running ? Reseat connector below short grey ribbon cable on driver board to start with. Then try reseatting ribbon cables and push home the square socketed chip on the CPU.

And that did the trick! Many thanks both to you and to the Mooseman for his sage advice!