Quoted from Jeffoto:I finally got around to this this morning, swapped out the chip with a new one and the dang commas are still there! Could it be Z1?
No, Z1 in not involved in the comma generation.
Devil's Dare is a SYSTEM 80A and Gottlieb use new 7's digits tubes on this series. The comma was not present on the previous SYSTEM 80, 6's digits tubes. To drive this additional feature, they add a new IC on the display boards : Z3, a 7432 - 4 x OR gate (only 2 used).
This circuit is intended to detect if a digit (or more) is displayed and in this case, activate the commas. If the display is off, the commas are also switched off. The detection is done by an OR gate between segments a, c and h (this is enough to detect any digit from 0 to 9).
2017-10-15_19h37_53 (resized).png
As ForceFlow said, the problem can be Z2 as it drive the high-voltage for comma "segment".
But it can be also the detection that don't work. So as G-P-E said, change Z3 (7432).
Another thing to check: there is not a short circuit on the connectors at the entrance of the glass tube. Check the pin 26 (comma) and contiguous pin 25/27.
Note that the regeneration procedure (by over-voltage on the filament) can not be responsible for this failure.
Brandenburg, KY
