Bally display problem - digits flash 7 when they should be blank.

[TopJimmyCooks]

examples - in attract mode:
Attract high score should be 945,450 - display shows 145,450
Attract blank for p2, 3, 4 no score should be ____00, shows 777700
Attract between flashes should be _______, shows 777777 or 222222

in test mode:
flashes numbers when show, sevens when blank between flashes.

What I did:
reflowed header pins, moved display to new slot.  problem identical in new slot, other display worked in the old slot.  so its on the board itself.

Decoder chip? 

[TopJimmyCooks]

I ordered the digit decoder chip.  $.50, worth a try.  Nothing else is indicated by the symptoms. 

[TopJimmyCooks]

Decoder chip worked.  replaced 6 resistors at the same time.  changed 2 transistors to fix a missing digit in one display from Globetrotter.  replaced the line filter on the marquee light for the ms pac man.  got halfway through a cap kit for ms pac man's 7203. 

I'm a soldering Mo Fo.