jr pac z80a weird problem...

mrbill2084

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I was working on a pacman with a jr pac pcb in it. I think it has a bad z80a. I will swap some z80a's and see what happens. I have some parts galaga and tron pcbs I can probably find one on..

Here is what they are doing.
board 1: It almost works. It will boot up. you can see the player 1 player 2 and high score, but thats all. In free play if you hit 1 player start, the whole screen will appear, but it locks up and never starts..

I happen to have another Jr pac pcb for pac that was doa. All you see is random characters on the screen on board 2.

So I swapped every chip between the 2 pcbs and no change. But when I swapped the z80a's, the problems moved to the other board. Board 1 now has the random characters. Board 2 now shows just the player 1, player 2 and high scores.. The only difference is that hitting the start button does not make the full screen appear and lock up.

Is it possible to have a partially working z80a?
 
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Is it possible to have a partially working z80a?


Sure it is, I have seen it before. Usually they either work or they dont but I have seen a couple that would boot then crash.
Try another z80 and see what happens. The only other reason the problem would follow with the chip is if it has some dirty legs.
 
Sure it is, I have seen it before. Usually they either work or they dont but I have seen a couple that would boot then crash.
Try another z80 and see what happens. The only other reason the problem would follow with the chip is if it has some dirty legs.

I think Riptor means another z80a.

I have a personal problem with Zilog z80 chips and will never use them.

They tend to work for some time and then give out once in a while, usually when testing just before shipping.

I go out of my way to remove and replace the Zilog z80x chips and I usually put in a socket. That is generally a good idea (sockets) so you can look at the logic if there is a problem later.
 
You have a problem with Zilog Z80s? Zilog is who made Z80, others are basically clones.

Yes I understand, Ford made the first car and the others are basically clones, doesn't mean that the original car is better.

This personal vendetta started when I was just starting in the arcade boards with the Galaga. That board had all three (3) Zilog chips, z80a's to B exact. I replace one and game worked for awhile then didn't. Replace another and same thing happened. I replace all three and game worked fine. Then tried to find the bad part by putting in one suspect in at a time. couldn't find one that didn't work. I spent several days on this until I got very angry. I turned green and got so big my clothes didn't fit. When I came to I had Ripped out every single Zilog z80x out of every single board I had at the time and replaced with other z80x chips and sockets.

Haven't had a problem with the z80's since.
 
I'll take all your Zilog chips!

Well since I was green and very big at the time; I didn't have proper cutters and used a dermal tool and cut right off at body of chip, not really usable. I only know this as when I awoke I had a pile of Zilog z80a chips on floor and a dermal in my hand.

If any come in that are in sockets; They are yours MajorHavoc..

I now put them Zilog z80x chips in a glass jar covered with a black silk cloth and surrounded with a ring of sea salt around the jar all to keep the evil Zilog spirits contained.
 
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You see the problem I had with Zilog chips.

YES; you can have a partially working z80x chip and it can push you to the edge.

Just get NEW z80a or z80b chips; sometimes it is cheaper to buy the faster chips but not always. !
*note: you can go faster but not slower!

ie z80 can be z80a or z80b; z80a can be a z80a or z80b...NOT a z80; Thus you can not use any other than a z80b for a z80b.

Once you do that don't try to go back and find the bad one!

I was working on a pacman with a jr pac pcb in it. I think it has a bad z80a. I will swap some z80a's and see what happens. I have some parts galaga and tron pcbs I can probably find one on..

Here is what they are doing.
board 1: It almost works. It will boot up. you can see the player 1 player 2 and high score, but thats all. In free play if you hit 1 player start, the whole screen will appear, but it locks up and never starts..

I happen to have another Jr pac pcb for pac that was doa. All you see is random characters on the screen on board 2.

So I swapped every chip between the 2 pcbs and no change. But when I swapped the z80a's, the problems moved to the other board. Board 1 now has the random characters. Board 2 now shows just the player 1, player 2 and high scores.. The only difference is that hitting the start button does not make the full screen appear and lock up.

Is it possible to have a partially working z80a?
 
The root of your problem was likely sockets.

the problems followed swapping z80a's, so it had to be the chip..

Just got done messing with the jr pac pcbs.. I went 2 for 2 pulling z80a's off bone pile pcbs.. Swapped the z80a's on both boards and now both are working 100%. I don't have a need for 2 pacman jr pacman pcbs, so if someone needs one, let me know. I have a super pac jr pac that was also doa. I will try swapping its z80a..

one board is missing a chip. I don't think I can easily find one, so probably go to HSC to get one. The chip is:
am9122-
35pc

Where is a go place to get z80a's? Jameco Is the 1st place I found and lists z80a at $2.95 and z80b at $3.25.

I don't think I have ever noticed a board with z80b. What games use that?

thanks for all th help!
 
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I am not sure what game specifically uses that part but I found that if I ordered the z80b chips they were much cheaper than the z80a chips..Like a $5 difference for the 3 of em. The faster chips were cheaper....go figure.

If the faster ones are cheaper go for it. I bought several last year when I was fairly new here and they have gone up since my last order. I got mine from mikesarcade.com and bought 10 or more of em. Z80a and I can use them where a Z80 is called for.

Riptor also sells them and is local to me. His site is in his signature.

the problems followed swapping z80a's, so it had to be the chip..

Just got done messing with the jr pac pcbs.. I went 2 for 2 pulling z80a's off bone pile pcbs.. Swapped the z80a's on both boards and now both are working 100%.

one board is missing a chip. I don't think I can easily find one, so probably go to HSC to get one. The chip is:
am9122-
35pc

Where is a go place to get z80a's? Jameco Is the 1st place I found and lists z80a at $2.95 and z80b at $3.25.

I don't think I have ever noticed a board with z80b. What games use that?

thanks for all th help!
 
one board is missing a chip. I don't think I can easily find one, so probably go to HSC to get one. The chip is:
am9122-
35pc

Where is a go place to get z80a's? Jameco Is the 1st place I found and lists z80a at $2.95 and z80b at $3.25.

I have 9112 in stock...only a few of them. http://www.twistywristarcade.com/ram/808-9112-ram.html
Im pretty sure Jameco sells used pull Z80's. I have Z80A and B, NOS. I have the "A's" in zilog or NEC brand.

Yes, Mikes arcade sells the z80B cheaper than the z80A. Not sure why, they are much harder to find and cost more. He must have bought a large stash for a good price at some point. There are not alot of arcade boards that require a Z80B.
 
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