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Pacland with rolling garbage

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Nes4life View Drop Down
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    Posted: 24 Feb 2018 at 10:19pm
Got a Pacland from @stegrey with rolling garbage on screen and no gameplay.

A rolling image on any PCB is usually a sync issue and, sure enough, no sync signal was being received at the edge connector. Looking at the schematics it seems this signal comes directly from Namco custom 27 at 6D and then goes through only a couple of ICs. Inputs were fine but output was dead. This custom generates the majority of the different clock signals that the PCB needs.

Replaced the custom with a known worker and the game was brought back to life! 

I noticed that every now and again the game didn't boot. It was running the tests and when it got to the ROMs it would restart. I hooked up the Arduino ICT from Paul Swan, ran the ROM CRC checks and all came out fine except the first 2 ROMs (8B & 8D) which were reporting the same CRC (and this wasn't a known one). This lead me to conclude that the IC controlling their selection was misbehaving. Replacing the LS139 at 7D fixed the issue.

Oh, and if you ever get vertical jailbars, just try reseating the IC labelled PL1-4








Edited by Nes4life - 24 Feb 2018 at 10:20pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote virtvic Quote  Post ReplyReply Direct Link To This Post Posted: 25 Feb 2018 at 12:10am
You're getting good at these...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote neil1637 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Feb 2018 at 6:47am
Very well done. As Vic says, you will get a reputation....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stevebm1 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Feb 2018 at 7:38am
,well done indeed,wish i'd hung on to the 2 non workers,I sold for £15 each years ago nowLOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smarty Quote  Post ReplyReply Direct Link To This Post Posted: 25 Feb 2018 at 9:40am
Nice write up and fix
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 25 Feb 2018 at 11:37am
I watched a CUS27 die before my eyes recently (sync jumped, then IC off completely and no clocks to anything).
Big issue with the older Namco games is there's nothing common and/or undesirable to rip bits off.
With System2 games, you can cannibalise broken Final Lap 1/2/3's for most of the custom chips.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stegrey Quote  Post ReplyReply Direct Link To This Post Posted: 25 Feb 2018 at 8:18pm
Thank you for taking your time to look and repair this for me phill and thanks to Jon hughes for sending the custom 27
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurray Banana Quote  Post ReplyReply Direct Link To This Post Posted: 26 Feb 2018 at 2:16pm
Another nice fix Mr Phil
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