Pacland with rolling garbage

[Nes4life]

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

Nes4life2018-02-24 22:20:30

 

[virtvic]

You're getting good at these...

 

[Mr20to5]

Very well done. As Vic says, you will get a reputation....

 

[stevebm1]

,well done indeed,wish i'd hung on to the 2 non workers,I sold for £15 each years ago now

 

[smarty]

Nice write up and fix

 

[John Bennett]

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.

 

[FinalFight]

Thank you for taking your time to look and repair this for me phill and thanks to Jon hughes for sending the custom 27

 

[Hurray Banana]

Another nice fix Mr Phil