ok disconnected each display seperatly,no change unfortunatly...

Geez I hope its not the master display shorted ! sounds like the same fault you had tho..

Ive got a hunch on all the 8s, theirs 2 Bcd to 7 segment decoders MC145437 on the discrete component master board,

one runs displays Master + 1-2 and the other displays 3-4,

will swap these Ics and see if the 88888888 fault moves...