Genesis Model 2 Controller Port Issues

[racketboy]

So I have this extra Genesis Model 2 that I got from a buddy a long time ago that has always had controller port issues.
I'm just now deciding to ask if anyone has any insight on it as it seems really odd.

Controller Port 2 (right side) acts completely fine.

I'm using controllers that work perfectly well on my other Genesis

But Controller Port 1 (left side) acts the following way:
C = Start
A and B don't work
Right doesn't work (other directions work fine)
Start doesn't function (C button functions as Start, but Start does not function as C)

[pierrot]

That's a pretty bizarre issue. At first glance it seems like it would be something wrong with the multiplexer in the controller itself, but if they are known to be working on other consoles, or in port 2, then that shouldn't be the cause. Have you tried multiple 3-button controllers in that port, with all of them displaying those exact symptoms?

There's not a whole lot going on in those controller circuits. As long as it's something electrical, and not mechanical, there aren't too many variables at play here. I'm thinking it sounds like a polling issue, and probably has something to do with the control signal line, from the ASIC. Maybe the EMI filter is bad, but I think it could be more likely that there's a problem with the termination resistor. It might be allowing for the signal to ring, and causing the multiplexer to switch when it shouldn't be.

That could be a bit of a longshot, though. There are a variety of tests that could be conducted for this, but the setup would be a little non-trivial.

[racketboy]

So I tried my 6 button controller on that port as well (swapping the two controllers essentially)
I mostly tested this on NBA Jam.
It does seem that "B" functioned as "C" as well. And it also seemed like "C" registered a "C" input right after the "Start" input as it paused the game with the first press and then un-paused and then immediately shot the ball when I pressed it again.

I haven't swapped a bunch of different controllers in there as my son was helping and didn't want to interrupt to much. But I'd be surprised if additional controllers would act differently than these two.

Thanks for your help!

[samsonlonghair]

That's a new one on me. I've owned a dozen different Genesi, but I never encountered that particular problem.

Just spit balling here:

I would open up the Genesis console. I think it's just standard Phillips head screws holding the case together. Once you have the console open, check the controller port for corrosion, crossed wires, or a short circuit. Blast it with electronic contact cleaner. That stuff is like the duct tape of the electronic world; it fixes everything. Scrub at it with a clean toothbrush too for good measure.

Honestly, Pierrot's answer sounds more scientific than mine. Eff it man, just open that Sega up and clean the inside as best you can. It's like when someone says, "turn the computer off and back on." It seems like a stupidly simple solution, but it works more often than not.

[racketboy]

Ok stupid question: what is this "Electronic contact cleaner" you speak of? Amazon link?

[samsonlonghair]

It's Petroleum distillate and alcohol in an aerosol spray. It's basically a mild acid that eats through the corrosion but doesn't harm metal, plastic, or circuit boards.

Here's what it looks like.
https://www.amazon.com/gp/aw/d/B000BXOG ... XA9DRCJRD8

I usually find it at car part stores or hardware stores. One can lasts me a while.

[racketboy]

Sweet -- thank you!
I'll add that to my collection.

Any other thoughts from anyone, please let me know.
I'll try to get this sucker opened up soon.

[pierrot]

Honestly, Pierrot's answer sounds more scientific than mine. Eff it man, just open that Sega up and clean the inside as best you can. It's like when someone says, "turn the computer off and back on." It seems like a stupidly simple solution, but it works more often than not.

This would really be the best starting point, anyway. I did a really poor job of outlining any real recourse, so thanks for picking up my slack, samson.

So I tried my 6 button controller on that port as well (swapping the two controllers essentially)
I mostly tested this on NBA Jam.
It does seem that "B" functioned as "C" as well. And it also seemed like "C" registered a "C" input right after the "Start" input as it paused the game with the first press and then un-paused and then immediately shot the ball when I pressed it again.

I haven't swapped a bunch of different controllers in there as my son was helping and didn't want to interrupt to much. But I'd be surprised if additional controllers would act differently than these two.

Thanks for your help!

Do the "A" and "C" buttons perform the same action in NBA Jam? I'm curious if you tested the "X," "Y," or "Z" buttons at all, also. If the issue is at all related to what I think it could be, those buttons would potentially give some funky inputs as well. I don't really know how the mux's inputs are configured in the 6-button controller, though.

If you have the chance to open up the console, and take some pictures of the traces and components around the controller ports, that could be helpful in ruling out physical damage.

[racketboy]

The three buttons do different things in NBA Jam, and the XYZ set doesn't function in NBA Jam.
Perhaps, I should throw Street Fighter in there and see how the 6-buttons work.
I'll keep you posted, guys!
Thanks!

[samsonlonghair]

Honestly, Pierrot's answer sounds more scientific than mine. Eff it man, just open that Sega up and clean the inside as best you can. It's like when someone says, "turn the computer off and back on." It seems like a stupidly simple solution, but it works more often than not.

This would really be the best starting point, anyway. I did a really poor job of outlining any real recourse, so thanks for picking up my slack, Samson.

Cheers!

Sometimes I overthink projects to the point of self-induced project paralysis. Other times I just roll up my sleeves, grab a screw driver, and start tinkering. A middle ground between those two options would probably work best.