I also don't know about the abacus controller, but I do know that a new 6 station timer is very affordable. I would recommend either a rainbird or hunter indoor? You can change it out very inexpensively. Just remember to label your wires before you take the old timer off of the wall. Pay extra attention to locate the common wire at the timer(Usually they are white in color).
If you want to nurse your controller back to life for another short period of time, I understand. If you need confidence in your system like we do down in Houston, Change it out. If the timer controller doesn't work down here, you can go on vacation for a week and come back to a dead landscape. I am sure that other parts of the country maybe more forgiving.
Good Luck
Dan
P.S. Timer cost at retail less than 100.00
Satisfaction of doing it your self Priceless.
Pay a Pro $250.00