Pacman trouble Garbage screen ,wont boot

[Denverlatino]

looking too see if any pacman owners have had this trouble so tehy can help me, i was looking at http://www.arcadegameover.com/pactrouble.html and the closest image i have says 4l video ram is bad, if thats the case, how can i fix it? if not take a look at mi pictures and let me know if you have experience fixing this.
Thanks allot in advance.

[Denverlatino]

found on mikesarcade.com that reseating Sync Bus Controller and cheking on it may fix prob, anyone knoows how to reset the Sync Bus Controller ?

[RetroACTIVE]

found on mikesarcade.com that reseating Sync Bus Controller and cheking on it may fix prob, anyone knoows how to reset the Sync Bus Controller ?

"reseat" the sync bus controller = "unplug it and plug it back in"

while its unplugged examine it for physical defects.

[whammoed]

found on mikesarcade.com that reseating Sync Bus Controller and cheking on it may fix prob, anyone knoows how to reset the Sync Bus Controller ?

Also, in case it's not obvious, the sync bus controller is this part:
http://www.mikesarcade.com/cgi-bin/store.pl?sku=SBC285

[Denverlatino]

sync bus controller looks ok too me, i found on mikesarcade page that if eproms are too rusty that might be the problem too, i wanna try to change 4L but not sure  how to do it, i know to replace 5f ill just buy a 2532 eprom and burn pacman.5f into it and that's all it needs , but to change 4L  I'm not sure what to  do, my thought is that 4L  its some kind of eprom i can just buy and install, am i correct?

[Level42]

It's a video RAM, not (EP)ROM. Ram is random acces memory. There is nothing stored in it until the CPU writes something to it. You can simply exchange the chip.

You could try exchanging the one on position 4L with one on another position and then boot up again. If the RAM itself is bad, the boot test should now show a bad video RAM on that other position you put it in. If it stays at the same position, you have bad contacts on the socket or something like that (bad trace).

[Denverlatino]

It's a video RAM, not (EP)ROM. Ram is random acces memory. There is nothing stored in it until the CPU writes something to it. You can simply exchange the chip.

You could try exchanging the one on position 4L with one on another position and then boot up again. If the RAM itself is bad, the boot test should now show a bad video RAM on that other position you put it in. If it stays at the same position, you have bad contacts on the socket or something like that (bad trace).

i was thinking on that too, i took off every single video ram chip and clean the thing up a bit, ill test tha board today too see if that works.

[Denverlatino]

Today i found a working ms.pacman and i got it for free, the guy offer me to take the whole cab but it look to beat up, so i just took the board, i didnt even had to trow away the old cab, anyway i think im gonna use this to test the pacman eproms 6,s and 5,s to see if they work. Wish me luck.

[Raven..]

Make sure the Sync Bus controller card on the PAC board is plugged in the correct direction.  If it gets plugged in backwards and powered up, it's toast!

[Level42]

http://users.adelphia.net/~68hc11/pacfile/pacfile.htm

[Denverlatino]

Im chaging all the eproms to the working ms.pacman board to see if they work, i just have a doubt, in order to make a ms.pac board a pacman board do i just need to remove the doughterboard and place z80 in its place plus change 5e and 5f, or do i have to change all 6's as well.If anyone knows please let me know. Thanks allot

[Denverlatino]

Im chaging all the eproms to the working ms.pacman board to see if they work, i just have a doubt, in order to make a ms.pac board a pacman board do i just need to remove the doughterboard and place z80 in its place plus change 5e and 5f, or do i have to change all 6's as well.If anyone knows please let me know. Thanks allot

anyone?

[D_Zoot]

Im chaging all the eproms to the working ms.pacman board to see if they work, i just have a doubt, in order to make a ms.pac board a pacman board do i just need to remove the doughterboard and place z80 in its place plus change 5e and 5f, or do i have to change all 6's as well.If anyone knows please let me know. Thanks allot

anyone?

Yes,  to convert a Ms. Pac back into Pac,  pull the Z80 from the aux board and place it in the socket on the game board in place of the ribbon cable.  Swap 5E and 5F and it's a Pac again!


I haven't been following this thread,  but are you getting just the garbage screen right from power up?  Does it change ever or is the garbage static on the screen? 

It sounds like the board isn't booting at all....


D

[Denverlatino]

I'm changing all the eproms to the working ms.pacman board to see if they work, i just have a doubt, in order to make a ms.pac board a pacman board do i just need to remove the doughterboard and place z80 in its place plus change 5e and 5f, or do i have to change all 6's as well.If anyone knows please let me know. Thanks allot

anyone?

Yes,  to convert a Ms. Pac back into Pac,  pull the Z80 from the aux board and place it in the socket on the game board in place of the ribbon cable.  Swap 5E and 5F and it's a Pac again!


I haven't been following this thread,  but are you getting just the garbage screen right from power up?  Does it change ever or is the garbage static on the screen? 

It sounds like the board isn't booting at all....


D

When i plug the board and turn on the whole thing, i get the garbage screen immediately, after i cleaned all the eproms and rams i got a different screen, its like two roads of letters and a gosth in the middle, the after i found this free ms pacman i have not had the chance to test the new board with the old pacman Roms, after i do that ill post results.
Now i will have to fix this board even if the newone works, so please keep an eye on this thread. Thanks allot.

[Level42]

Check if the reset line on the CPU is constantly active (low). If so, temporarily put +5V (from a testpoint or other known +5V spot) on the reset pin of the CPU. See if anything happens...

[Denverlatino]

Check if the reset line on the CPU is constantly active (low). If so, temporarily put +5V (from a testpoint or other known +5V spot) on the reset pin of the CPU. See if anything happens...

what pin number its the reset line at cpu, its a pin on z80 or something in the motherboard, thanks allot.

[Level42]

Z80 pin 26

Google is your friend in these kind of things:

http://www.howell1964.freeserve.co.uk/parts/Z80_CPU.htm

[D_Zoot]

When dealing with Ms Pac boards, something to try first is pull the ribbon cable from the main board and install a known good Z80, no need to swap roms for this test.   That will tell you if the problem lies with the mainboard or the aux board/ribbon cable/Z80, board boots = issue with aux board, cable or Z80, board still doesn't boot = issue with main board.


You can swap the Z80 from the aux board and install that just to rule out the aux board and cable, but I usually use a known good Z80.

To explain further,  a Ms Pac should boot and play without the aux board and a Z80 installed on the main board and with Ms Pac roms still installed at 5E and 5F,  you'll just get incorrect characters.


D

[Denverlatino]

When dealing with Ms Pac boards, something to try first is pull the ribbon cable from the main board and install a known good Z80, no need to swap roms for this test.   That will tell you if the problem lies with the mainboard or the aux board/ribbon cable/Z80, board boots = issue with aux board, cable or Z80, board still doesn't boot = issue with main board.


You can swap the Z80 from the aux board and install that just to rule out the aux board and cable, but I usually use a known good Z80.

To explain further,  a Ms Pac should boot and play without the aux board and a Z80 installed on the main board and with Ms Pac roms still installed at 5E and 5F,  you'll just get incorrect characters.


D

ms pacman works perfect, the problem is on pacman board, i have not had the chance to test pacman 5e and 5f on the mspacman board to see if theres an eprom problem , as soon as i get the chance to test the ill post results 

[D_Zoot]

ms pacman works perfect, the problem is on pacman board,

Oops!  Guess I didn't read the whole thread close enough!


Anyway, earlier you asked about the row 6 roms,  yes, problems with one of the row 6 roms can prevent the board from getting thru the boot cycle.

Did you ever get the chance to find out what the reset was doing and determine if it's watchdogging?


D

[Denverlatino]

ms pacman works perfect, the problem is on pacman board,

Oops!  Guess I didn't read the whole thread close enough!


Anyway, earlier you asked about the row 6 roms,  yes, problems with one of the row 6 roms can prevent the board from getting thru the boot cycle.

Did you ever get the chance to find out what the reset was doing and determine if it's watchdogging?


D

I did not have the chance to test the reset, problem is i dont have a cab at home to test the boards ,and the one i got ofered with, was way to beat up to take home, (wife would get mad) so the only way i have to test these boards its by going to the dealer friend i got and borrow his cab, he told me he need it a favor and that he will pay me with the cab if i made that favor to him, so i guess by next thursday ill have that cab at home and i will be able to test these boards step by step at home to se what s wrong with the one that does not work. Until then i guess ill have to wait, but please keep an eye on these thread i really need some help. Thanks allot. 

[Denverlatino]

here's an update on this issue, i change every single ROM,or removable chip from the working PCB to the non working PCB , with all the chips from the non working PCB the working PCB worked just fine, so I'm pretty sure its not a ram or rom problem , i also changed  video and ram boards as well and they seem to work too, i still get the garbage screen , so i really don't know where else too look, any help will be appreciated. 

[Denverlatino]

Also in the working PCB i noticed that the bonus characters are wrong , for example on the first maze i eat a cherry but on the bottom i see a can of soda, i don't exactly remember every single one but anotherone is that i ate an apple but at bottom i see some grapes, and so on, does this means i got my bad characters on ROM 5e or 5f?

[D_Zoot]

i also changed  video and ram boards as well and they seem to work too, i still get the garbage screen

You mean the Sync Buss Controller and VRAM Addresser boards?


Since you've ruled out the ROM's, RAM and CPU, you've got to have a logic problem somewhere on the board, there's a large number of things that it could be, any suggestions at this point would only have you shotgunning IC's at it, and since all of the supporting logic is soldered instead of socketed, I wouldn't recomend that.

Time to break out a logic probe or scope and see what's actually going on with the RST, CLK, Address, Data, etc. circuits.   Other than that, you may have to send the board out for repair.  There's a number of folks that do Pac board repairs, and honestly they are pretty reasonably priced.


D

[Denverlatino]

i also changed  video and ram boards as well and they seem to work too, i still get the garbage screen

You mean the Sync Buss Controller and VRAM Addresser boards?


Since you've ruled out the ROM's, RAM and CPU, you've got to have a logic problem somewhere on the board, there's a large number of things that it could be, any suggestions at this point would only have you shotgunning IC's at it, and since all of the supporting logic is soldered instead of socketed, I wouldn't recomend that.

Time to break out a logic probe or scope and see what's actually going on with the RST, CLK, Address, Data, etc. circuits.   Other than that, you may have to send the board out for repair.  There's a number of folks that do Pac board repairs, and honestly they are pretty reasonably priced.


D

could it be a power problem? also because of my first lenguage its spanish, sometimes i dont fully understand the terms used in here , what do you mean by a logic problem? something on the circuits or on the soldering points? i really dont know what rst,clk is. Thanks to google and the wiki i now know what a logic probe is, so i gues i will have to use that pen to test every point on the board to see if is working properly, maybe even the power source as well.
Also on the bonus characters issue of the working board ,do you think thats because of wrong  roms at 5e or 5f?
Thanks allot for your help.

[Denverlatino]

Check if the reset line on the CPU is constantly active (low). If so, temporarily put +5V (from a testpoint or other known +5V spot) on the reset pin of the CPU. See if anything happens...

With so many messages posted i forgot about this one, ill do this today and post results. Thanks allot.

[Denverlatino]

Check if the reset line on the CPU is constantly active (low). If so, temporarily put +5V (from a testpoint or other known +5V spot) on the reset pin of the CPU. See if anything happens...

I did this and the garbage screen only seems to change, thats it. 

[Level42]

And if you hold it a bit longer ?

[Denverlatino]

And if you hold it a bit longer ?

If you mean like more then 1 minute, nothing happens.

[Level42]

Too bad...

[Denverlatino]

Too bad...

 
So that means, my board its death?

[StephenH]

Here is some more info I found on Pac-Man boards:

http://users.adelphia.net/~68hc11/pacfile/pacfile.htm

[Level42]

Too bad...

 
So that means, my board its death?

Just thatI don't have more clues for you....

Did you check out that link I posted here ? There's a lot of info there.

[Denverlatino]

if i mess with the roms at the working pcb, i get the same garbage, but if i place the working roms on the non working pcb i still get the static garbage, could it be posible that pcb married to theyr roms?