I received three boards from my friend Enrico for repair, this is the first one a bootleg board of Legend of Hero Tonma:
Legend of Hero Tonma is a side scrolling platform game released by Irem in 1989 on his M72 hardware platform.
Powering up the board ends up with this scenario:
… a solid white screen on boot, so i had to start the troubleshooting by inspecting the NEC V30 cpu, an 8086 pin compatible CPU. Here is its pinout taken from its datasheet:
Looking at its control pins with the scope didn’t reveals anything useful to solve the boot issue, so i had to deeper investigate on the address and data bus. Anything seems to be healty except when i put the probe on AD0 pin 16, the signals look weird. So i’m pretty confident and removed the CPU from its socket. Doing this reveals a very loosen socket, so it must be replaced to prevent further issues. Once the CPU has been pulled off, i can spot 2 broken traces under the CPU, one of them goes to/from pin 16. I promptly fixed them:
The CPU socket wasn’t in good condition so i removed it:
… and replaced it with a brand new one:
Now i’m ready for the smoke test, fingers crossed as usually and power feeded to the board. I was greeted with a solid black screen, a sign that something has been changed, but the board is still in not working, but i lightly heard some kind of music coming out from the speakers, pumped up the volume, and yes, the board is running i can coin it up and start a new game, but it still playing blind.
Touching around the board restore temporarly the background and the sprites, so i had to spot the failure. It ends up with a loosen contact on the flat cable connector that join the the PCBs.
So i removed, cleaned and reflowed it on the solder side. I powered up the board again and …
Yeah! It works! Now it’s time to a deep test ingame! 🙂
Board fixed, another case closed!