PAL Mega Drive - black screen and strange region issue

[brmanuk]

I'm trying to fix my friend's unmodded Mega Drive and I'm totally stumped.

When a cartidrge is in, the console displays the "Produced By..." license but then it's followed by a black screen. None of the games I tested would boot, aside from Rambo 3 which booted a grey Sega screen with a white box where the Sega logo should be and then crashed.

Weirdly, some games (such as Street Fighter 2, Aladdin) boot but they display a region message despite being a PAL game on a PAL console!

I've thoroughly cleaned the cartridge slot and re-aligned the pins but no dice. I've taken the console apart to look for bad soldering joints but haven't found anything.

Anyone have any ideas?

[segasonicfan]

The first thing you want to do is take a dive into the Genesis II service manual. Look at the schematics and identify the PAL region pin on the main ASIC. I'd imagine that you possibly have a short on that pin. a lock after TMSS usually indicates Z80 issue, but since you have some games booting I bet you have a short or maybe even a broken trace to the cart slot. .

I'm developing a detailed repair guide for issues like this, but since it's unpaid labor and my schedule is packed ( and I have bills up to my ears ) I probably won't be finishing it anytime soon. Check back on my site later though, cause it will be going up at some point.

Also be sure to check the Genesis 1 service manual that I added links to in the service manual thread by omp. It has a super useful flow repair chart in there.

[serbusfish]

Sorry to hijack but I am unable to make threads so wondered if someone could help.

I recently did a 10mhz overclock mod on my model 1 mega drive. This worked but there must have been a bad solder joint somewhere as my switch sometimes did nothing, so I went back and re-soldered my joints, however I foolishly forgot to unplug the console from the mains.... when I booted a game the SEGA logo was all messed up and glitched, and now I just get a black screen 99% of the time. Did I fry the console?