Lurch666
Well-known member
5D is an LS20 and 5E is an LS02
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No changes after swapping 8F.. but the ic is showing good now
7J also an LS139 is also showing good
3 x 74Ls367 has bad outputs..
but also piggybacking had no effect.. is it normal? I thought piggybacking of a good ic "overrides" the bad ic
I see..
LS20 on 5D is checked with a logic probe.. all inputs and outputs are toggling. But no logic analyzer used..
I'm trying to swap the NAND Gate on 1D first before i looking for other possible issues
No.. I haven't those ic's tooIf you have spare LS20 and LS02 chips spare it couldn't hurt to piggyback them while you wait for the other chips.
It might not make any difference but it's worth a try.





I see..
LS20 on 5D is checked with a logic probe.. all inputs and outputs are toggling. But no logic analyzer used..
Have to order ls20 and ls02 to check 5D and 5E.. games works, sounds is well.. Highscore screen looks correct. The combination with background and sprites screw upEven though the outputs are toggling the logic probe won't tell you if those are the correct outputs.
I still think your graphics are coming out correct,just not being displayed at the correct times hence why I'm guessing it's the end of the video output circuit that has issues.
Update: I guess the floating signal is correct. The address lines comes directly from the z80 and the address bus isn't pulled high or low.. so when no address is set the output is floating
I got ls02 and ls20 today. I piggybacked 5D and 5E but no changes.. I tried all other ls02 on the pcb too..Did you check 5D and 5E?
Aren't those PLAs on the schematics?Piggybacking of 3E and 6E -> 74LS368 no changes
Piggybacking of 4E ->74LS365 no changes
https://jammarcade.net/popeye-tech-info/ here you can see that the PLA's are normally logic ic'sAren't those PLAs on the schematics?


