Pacman board problem? invisible fruit

SaminVA

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I thought my Pacman was working 100% again but I just noticed it has invisible fruit under the ghost's box during game play. Sometimes in the later levels you will see numbers like 200 where the fruit should be and when Pacman eats it ,it will put the score number where the fruit should have been, like 700 or 1000 and it adds to the score. Anyone see this before? Could it be a ROM problem? Everything checks out OK in self test. It has the fast ROM chip and in the first intermission the big pacman chasing the ghost looks like his bottom jaw is missing. In the video right at the beginning when I drop in a quarter you can see the number 200 in between the words Game Over.
Any Idea's
Thanks
 
Reseat all the 2114 rams and check the two eproms on row 5. Most likely either a ram socket or rom socket problem.
 
Test mode showed no problems. I am going to try Riptors suggestions. Going to reseat all the socketed chips first and if that doesn't fix it I have a new set of Eproms on the way to try and if that doesn't fix it I'll try the sockets next. I ordered a new set of Eproms for my second Pac board because the ROM legs are rotten and breaking off. :)
 
It's most likely a bad 7489 or a cracked resistor pac.

Reseating the 2114s won't do a damn bit of good, as ram connection problems would show up in self-test.
 
It's fixed, we now have FRUIT in the attract screen and in game play.
I first installed a new set of ROMs, even put the original speed ROM back in and no change.
I then removed all 6 of the 2114 Ram IC's and swapped them with the 6 from my non working Pacman board.
I powered it up and the same thing, No fruit so that means all 6 2114 Rams were good.
Next I swapped the V-RAM Addresser board with the one from my non-working board and YES I now have FRUIT and the big Pacman in the first intermission now has a bottom jaw. So the problem was in the V-Ram Addresser board. For now I left the original speed ROM in the board. I think I would rather have my game original for now as the speed up seems to be just a hack. I might consider installing a 96 in 1 some time in the future. Now to figure out whats wrong with board # 2. I replaced all the ROMS and the board is completely dead.
 
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I had posted this I another thread as I had a question about a 74LSXX chip I was having problems with and I forgot about this one so here is a reprint of the Fix for the missing Fruit on my Pacman board.

Well problem solved and Pacman board # 2 is fully working again. So here's a recap of what I did.
I first replaced U10 (74LS02) with no change. Next I replaced U2 (74LS257) with no change. Then I replaced U9 (74LS86) because when I piggy backed a new 74LS86 the missing fruit started working but when I replaced the old chip with a new one not only was my fruit missing again but Pacman and the ghosts were missing too. I tried piggy backing 2 new 74LS86 chips but it didn't work so I put the old SN74LS86N back in and started checking again with my logic probe. I noticed by applying the probes tip to certain chip pins it would make the fruit appear. I did this testing with the game froze on a screen that should have the missing fruit displayed buy switching dip switch 8. I then probed all the pins and wrote down all the chip and pin numbers that made the fruit appear. Turns out I got the most active pins on chip U5 (74LS157) and a couple of pins would produce part of the fruit so I de soldered it and put in a socket and put a new 74LS157 and now I had my fruit back. I then decided to put one of the new 74LS86 chips back in U9 and it still worked so their was nothing wrong with the 74LS86 chip so I guess the bad U5 (74LS157) was causing it to appear like it was bad.
So if anyone wants to add this to their Pacman repair logs Here ya go.
If your game is missing the Fruit in both attract mode and game play and the large Pac man chasing the ghost in the first intermission is missing his bottom Jaw then U5 a 74LS157 is bad. That's the chip in the middle of the V-RAM Addresser board.
One more board fixed so many more to go. I guess Frogger is next. :D
 

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