May 052018
 

I got a dead World Rally 2 which upon boot showed garbage but I could hear that the monitor was hissing, meaning that there was no proper sync.

 

I immediately checked the two OSC on board and found the main one, 26mhz which is driving the 68k and pixel clock dead.

The 26mhz is not very common but I managed to found it on another Gaelco board and replaced it.

Game still didn’t start and was out of sync, but the 26mhz signal now was present

Near the OSC there is a 74ls74@IC29  which divide by 2 the clock for the 68k which runs at 13mhz.

The output of the flip flops was completely dead.

Replacing it I got this time a black screen with no activity.

First thing I did without much hope was to check the program eproms , normally it’s very rare that they fail but to my surprise both eproms had pin 31 not connected internally!

Replacing eproms with good ones fixed the game completely.

Last think I did, was to change the DALLAS MCU battery since it was at 2.9V , very near to suicide.