Sega Mega drive 1 freezes

Hello,

I bought a pal sega mega drive model 1 that does not work properly.
I can boot up a game from the first try but after playing for 30 seconds the game starts to glitch and eventually freezes. In the glitched graphics it displays the message "illegal instruction".
After this happens I cannot boot up any game, I just get a black screen.

Does anyone know what the problem might be?

Thanks!

 

Are you experienced in electronics?
It could be cold joints warming up, or the 68k going mad, or some chip acting strange when hot. First of all clean your board well and check for visual damage. I'd suspect the datapath to be the culprit actually, as you can see graphics and such. Try to check catridge connector, traces to and from RAM and traces to and from CPU. If you can solder, reseat RAM and CPU and try to see what happens. That's what I'd do.
I've also heard of people who reflow electronics in a kitchen oven, but I know nothing about that.

 

Unfortunatly I'm not experienced in electronics.

I've taken the mega drive apart but can't seem to find visual damage.
There is nothing that gets really hot when the console freezes.
If I reflow solderjoints, where should I start?

 

Start with the cart slot. Then move onto the Z80 (should say Zilog Z80) and the 68K CPU (largest chip behind cart slot). Be careful reflowing chips so you don't make any bridges.