OK now I'm worried.

I just had a look at the schematics for the large display and it seems that the HV is generated on the board itself (+5vDC, +12/24vDC)....Normally on DMD games you can have upwards of 100vDC which is quite dangerous...

BUT any loose wire hanging from the machine is not a good thing, and not only for safety but the risk of damaging more components is quite high.

Those large DMD's are very very expensive..

For service call - Firstly try the seller, I'm sure they will send a tech...
Otherwise try Bumper Action (their new prices are on their website and quite reasonable)
Pinball Fixers are still in operation I think (google search their website)
Zax Amusements (Port Melb)
240 Amusements (Hallam)