This is one for the repair logs:
Repaired and bulletproofed a nice BZ PCB set and let run to burn in. The next day I could not get it to play. I turned it to test mode and the fire button was firing repeatedly. I checked the fire switch and it was open (not firing). I power cycled and it stopped. In test mode, I went to scope the pokey and every time I brought my finger close or touched the top of the pokey, I could get the game to fire. Weird. Tried another Aux board and it did the same thing. So on to the AVG board. I looked on the o'scope and I could see some noise and changes on P2 (74LS273). I piggybacked another on top and the problem disappeared. I socketed and replaced the 74LS273 and now the board is happy once again. Ran it for a day and a half with no problems.
Bill
Repaired and bulletproofed a nice BZ PCB set and let run to burn in. The next day I could not get it to play. I turned it to test mode and the fire button was firing repeatedly. I checked the fire switch and it was open (not firing). I power cycled and it stopped. In test mode, I went to scope the pokey and every time I brought my finger close or touched the top of the pokey, I could get the game to fire. Weird. Tried another Aux board and it did the same thing. So on to the AVG board. I looked on the o'scope and I could see some noise and changes on P2 (74LS273). I piggybacked another on top and the problem disappeared. I socketed and replaced the 74LS273 and now the board is happy once again. Ran it for a day and a half with no problems.
Bill

