sms sms repair question; permanent directional left...

[yashiro]

okay, so i have a master system that treats controllers as though left is held down. (sort of like what happens if you put alien syndrome into a power base convertor). but,

a) this isn't a power base convertor, it's an original sms, and

b) it only does it with original master system controllers.

yeah, if i plug in a genesis controller instead, it works just fine. so it isn't like i can't play it or anything, but occasionally i just wish i could use the original controller. i dunno, nostalgia, i suppose.

anyway, anybody else ever had this particular problem. i skimmed through the forums and didn't see it anywhere, and i'd very much appreciate any suggestions. i thought it was the port until i realised the genesis controllers work fine, and now i don't really have any solid ideas.

thanks!

 

[ExCyber]

I'm not sure what could cause this. A few questions I have:


Does it happen with all games?

Does it happen in both ports?

Does it happen with different SMS pads?

 

[yashiro]

it's happened with several games (i have yet to find one that it doesn't...)

not sure about port 2. i'll have to check it out.

yeah, i've tried several sms pads, and they all work in my other machine, and they all malfunction in this one.

i've got everything fairly handy; i may hook everything up tonight and test it more thoroughly (both ports, more games, etc).

 

[yashiro]

it malfunctions even with no controller in the port. with an empty port, the game will react as though the left direction is held down.

with the genesis controller in place, everything works normally.

also, it's only controller port 1, not port 2. all controllers, including sms controllers, work just fine in port 2.

any ideas?

 

[ExCyber]

The only thing I can think of is that there could be a relatively high-resistance connection between the "left" pin and ground inside the SMS, such that the mux in the Genesis pad can "win" when driving high, while an SMS pad can't drive it enough to register a high logic level (not sure what an SMS pad uses, but I would expect just pull-up resistors...).

 

[Chilly Willy]

Check the 5V line while you're at it. Maybe it's gotten far enough away from 5V to cause odd happenings. (Just grasping at straws here )