SaminVA
Well-known member
Is their a difference in a SN74LS86N and a 74LS 86
I guess I could have a bad batch. The second Pac man board that was in the bottom of my Pac man cabinet when I bought it works but it was missing the Fruit. I tracked it down to a problem on the V-Ram Addresser aux board. Swap the board between boards and the missing Fruit moves with V-Ram Addresser aux board. So I figured it's a bad chip on the aux board and it only has 10 IC chips so I ordered 5 of each chip from Bob Roberts. I got out my logic probe and started poking around thought I had found the problem twice and replaced both chips with no change. Then I noticed if you put the probe on one pin on one of the SN74LS86N the fruit would appear so I took one of the new 74LS 86 and piggy backed that chip and the fruit appeared and the game played fine. I remove the chip ,put in a socket and the new 74LS 86 and I still have no fruit and I lost my Pacman and ghosts but he still chomps the dots.
I put the original SN74LS86N back in the socket and it works but I am missing the fruit. Piggy back the new 74LS 86 on the old chip in the new socket and the game works. It's strange. Could the new chip be bad or just isn't the same as the original chip?
I guess I could have a bad batch. The second Pac man board that was in the bottom of my Pac man cabinet when I bought it works but it was missing the Fruit. I tracked it down to a problem on the V-Ram Addresser aux board. Swap the board between boards and the missing Fruit moves with V-Ram Addresser aux board. So I figured it's a bad chip on the aux board and it only has 10 IC chips so I ordered 5 of each chip from Bob Roberts. I got out my logic probe and started poking around thought I had found the problem twice and replaced both chips with no change. Then I noticed if you put the probe on one pin on one of the SN74LS86N the fruit would appear so I took one of the new 74LS 86 and piggy backed that chip and the fruit appeared and the game played fine. I remove the chip ,put in a socket and the new 74LS 86 and I still have no fruit and I lost my Pacman and ghosts but he still chomps the dots.
I put the original SN74LS86N back in the socket and it works but I am missing the fruit. Piggy back the new 74LS 86 on the old chip in the new socket and the game works. It's strange. Could the new chip be bad or just isn't the same as the original chip?

