LeMans PCB Repair Log

Lemans arrived in the Repair Station DOA.  The main fuse appeared blown so I replaced it.  With fingers crossed I turned on the game and was met with a full raster screen but it was blank.  After repairing the edge connector and a few other cracked solder joints I had the screen of random errors as shown.  It appeared to be a horizontal double split screen but didn’t look anything like the Lemans I remembered playing!  Interesting enough the game would coin up and the start button would light up....so that was good news.  Upon pressing the start button I was met with a very loud ‘roaring noise’ which was very annoying.

After spending quite a bit of time analyzing the circuits that I believed were at fault, I discovered the chip located at E6 was a potential reason why my track was not displaying properly.  My logic probe confirmed this.  However, I still did not fully understand the split screen issue which appeared unrelated to the track display problem.

I was amazed at how detailed the Atari Lemans manual was for this game.  It clearly explained each circuit and its associated function.  I knew if I had a chance to figure out this split screen issue it was going to be by reading and understanding each of the circuits.  When tired of reading, I rebuilt the Motorola XM701 monitor chassis and was finally able to dial in something that appeared to be the correct color for the screen.

After further analysis with the logic probe, I was very confident my problem was contained in the synchronization and blanking circuit.  I took tons of notes on my readings and sure enough I found a chip located at H2 which was in question.  It was one of the first chips in the beginning of the circuit and when compared to the chip schematic for IC 7474 it wasn’t reading anything close.  So I decided to dive in and replace a chip on a board which had not seen melted solder since 1976!  With H2 replaced, I actually had what resembled a Lemans screen and a car able to drive around in first gear!  Progress!

I admit I had some fun driving around in first gear but I knew I had more problems to solve.  I now believed I was down to just the track display issue so I went back through my notes and looked at the E6 location which was a 74165 chip.  I replaced it and almost fell over at the results!  GREAT!  I now had a working game with the clock/score and everything running the way I remembered it!  I still had only first gear but soon realized the shifter had seen years of abuse and needed to be rebuilt.  The game is now running pretty solid!  I believe I still may have a shifting sound issue but from arriving DOA...things are looking pretty good!