Update: It's alive!! I gave it a proper vacuum cleaning (it had layers and layers of dust) and replaced a fuse and it's working now!, somewhat.
This is a Rave Racer cab, but has a Ridge Racer main board, someone downgraded it at some point possibly due to a faulty Rave Racer. There is no input or sound but there is video and I can see no graphical problems so far.
Once I can confirm the IO board wiring I'll get one.
I don't leave it on for long because the monitor although seems to be working, it's making a very loud continuous buzz (nor more clicking). I should probably check that out first.