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Joshuart311
Member
Ok so I checked all my EPROMs and they checked out good. I can't find a broken trace on the board. Any suggestions?
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ms. pacman help
- Thread starter Joshuart311
- Start date
Riptor
Well-known member
Got a logic probe? Check for clock and reset line, swap in a known good Z80 if you have one.
Have you checked the 5v on the board already? Measure across C3 or at an eprom.
Have you checked the 5v on the board already? Measure across C3 or at an eprom.
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Joshuart311
Member
I don't have a logic probe yet. Swapped z80 with known good. No change. Have 5.06 v on board at c3.
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Joshuart311
Member
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Joshuart311
Member
Ok so I guess my next step is a logic probe. I saw a great write up on lawmowermans page. So going to pick one up tomorrow. Also I found a guy in Texas who has a few games from an arcade/go kart place. Going tomorrow to view them. I'll post tomorrow his info in another thread in case anyone is interested.
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Joshuart311
Member
Ok so I went back to check voltages on the board because I wanted to write them down. I first checked c2. C2 had 5.18 vdc. When I checked c3 it had only .551 vdc. So what would cause it to not have 5 v? Bad cap?
Riptor
Well-known member
If you have it at C2 you should have it at C3 also. Check the board for damaged traces.
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Joshuart311
Member
Ok so I resoldered the cap at c3 and now have my 5v. I went to get that logic probe at radio shack and they acted like they never heard of one before. So I'm going to order one tonight. I was supposed to go through some games today but someone beat me to it and bought the whole lot. so cancel what I had said about my warehouse find.
Also having the 5v didn't change anything board still does the same as before.
Also having the 5v didn't change anything board still does the same as before.
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Joshuart311
Member
Update: I decided to go ahead and remove the VRAM addressor socket and the sync bus controller socket. I found 2 broken traces at the sync socket. Waiting on sockets from riptor and will post when I get it back together.
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Joshuart311
Member
I installed the sockets and repaired the two traces that were broken. I also lost my +5 again at c3. Installed a jumper and it is now back. Now I'm getting tons of moving garbage on the screen. So I know the board is trying to boot. Is there a logic sheet on this (other than the schematics)? I was wondering if there was just a list of what's high and what's low per chip? Any other ideas guys. Im closer now to getting this board working and refuse to give up.
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Joshuart311
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Ok I have a new question. Would it be beneficial to use a logic probe on my good ms PAC board and test and write down each pin? Then use that information to check my non working board? Or would that be a waste of time? Also if I have a pin that should be high and low pulsing, but is only low pulsing, what would be the next step?
musicman282
Active member
You could compare the information from the working board which would probably take a lot of time or you can just google the number from the chip and find the data sheet for the chip and use that info to see if the chip is behaving correctly. Do you know anything about digital logic?
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Joshuart311
Member
Im new with digital logic. I am making small amounts of progress understanding all that i'm reading about it. I did order the ttl cookbook and a couple other books to read up on and get a better understanding. I've always been interested in this sort of thing and just now have the money to invest in it. I have a good job so im not trying to make a career but I would like to be able to repair my own boards (friends also). I know with the progress im making i should have this pac board repaired in a few years. LOL
