Trying to repair Mark's Amstrad CPC464: Part 4 (Fixed!)
22Massive thanks to Aaron @WacKEDmaN for taking over the troubleshooting and ultimately fixing Mark's CPC ... there were ten separate faults ... if you count the DRAMs separately! Yikes!
I initially identified the 40010 gate array as being faulty - not outputting any clock. I replaced it with one of mine which looked to be working - outputting a clock - but still no video output.
I had to travel to Melbourne for a few weeks and Aaron kindly offered to take a look. I had put a socket in for the older 40007 gate array but Aaron noted that it required two large resistors that I had neglected. Putting these in (covered in heat shrink) along with a 40007 finally got a video image ... albeit corrupted!
Further work by Aaron, painstakingly de-soldering and socketing logic plus all the DRAM identified a 74LS153 (4-to-1 multiplexer) and a 74LS244 (buffer) as being faulty.
{Updated}
Additionally seven (out of eight) of Mark's 4164 DRAMs were faulty, identified by running a diagnostics cartridge.
Man, what a mess of a board!
Again, big thank you to Aaron for his patience in identifying all the faults!