My Sega Genesis/Mega Drive II get stuck (the image on the screen seems frozen) after some incidents that occurred to it. It doesn't matter when that is happened, which game did I play or even how hot is it gets. For instance, it happened when it bump from something, like from moving it the slightest with the cord (because it's really short).

But my major concern is when I leave it still, at some pause menu, for a while (because, you know, there weren't so many games for it with a save feature), let's say, for an hour. I can fix it if I'll push the reset button, of course, but the temperature of the Mega Drive is still somewhat between 60°C-80°C.

I don't know if it's a defect with the production, or is it only with mine. I suspect this is happening because of a loose connection between the controller nor the cartridge, because it happened even if staying at "idle" after a while.

I suspect that the reason is due the overheat of the component circled in this image:

A motherboard with a tall, silver electrical component circled..

  • Welcome to Retrocomputing. Thanks for the detailed information; I'll edit your question to make it a little clearer to other people what the problem is. Thanks also for trying to find the solution yourself; there are too many people who expect that there's a magical solution to "my computer doesn't work, halp!". I hope you get an answer soon.
    – wizzwizz4
    Dec 5, 2016 at 21:29
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    Loose connection/bad solder point etc. and overheat are both possible causes. You can test for overheat by providing better ventilation: Use it when opened, with maybe an external fan aimed at the board, and see if the problem still happens.
    – dirkt
    Dec 5, 2016 at 21:44
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    @wizzwizz4 no, it looks like a TO220 part (very likely a power transistor or linear regulator) with a big heatsink bolted on.
    – hobbs
    Dec 5, 2016 at 22:26
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    @HashiramaSenju okay, yes. The board diagram confirms that that's IC12, a Toshiba TA7805S. That's a 5-volt linear regulator in TO-220 form factor. There are a million compatible parts, generically called "7805". That one is listed as having a max operating temp of 75°C. It's a part that normally gets hot, so that might not have anything to do with your problem.
    – hobbs
    Dec 5, 2016 at 22:33
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    I don't have access to it at the moment, but my old Mega Drive II exhibits the same behaviour; a small knock will make the game freeze indefinitely, requiring a reset/restart.
    – Francis
    Dec 7, 2016 at 9:25

1 Answer 1


Heat could be a problem, and given the description, probably a factor. There could be a dodgy part working at the edge of its working parameters or at its useful life. There could be a physical problem with a board connection that manifests when things get hot enough.

Really, besides looking for obvious loose connections and flexing the board gently to see if you can cause the problem on demand, the only way to really solve this is with a multimeter and an oscilloscope. The idea is you work backwards and forwards through the circuit looking for where signals, levels, and clock lines seem to have a problem. Those edges are where the problem lies. Then you have to know how different components react to generalize the problem to a loose or failing part.

As you can imagine, this takes a fair amount of experience debugging circuits. You may get lucky with your initial attempts, and you have to start somewhere.

It is unlikely the power transistor you identified is fault, but there are ways of testing them to find out. You have to desolder one of the emitter or collector leads and treat them as two diodes to check that they are good.

I would be remiss if I did not point out that specific electronic debug questions might be better over on EE.SE. If you keep the questions on topic you can leverage a lot of experience in these things over there. That is, getting a console to work is not strictly a retro thing at some point.

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