Weird problem with SMS (Original version, Model 3010)

[gzsfrk]

Hey there! Hoping someone might be able to help me with an issue I'm seeing on a new SMS I picked up.

 

It's the original version (model 3010) with no pre-loaded games on the console. (Also note that this is my second SMS; I have a main that works perfectly with everything I throw at it, including all the cartridges mentioned below.)

 

The problem is this: when I turn on the console with some games plugged in, it works just fine. Examples include The Ninja, Global Defense, Choplifter, Hang On/Safari Hunt combo. But when I insert other cartridges, it starts up, shows the Sega logo, plays the "Sayyy-Guhhh" jingle, then displays the screen telling me to insert a cartridge. No software error or anything like that. Examples of games which fail to load are Outrun, Sonic 1 & 2, Mortal Kombat, and about 66% of the others I tried. I'm not sure, but I suspect that the games which are working are those which have relatively small ROMs to load, whereas those which fail and the larger memory releases. I disassembled the unit and checked both the pins inside the slot (all pins look like they have plenty of flex to make contact with the cartridge, and I've cleaned them three times with 1000-grit sandpaper and an alcohol soaked slot cleaner) and the solder points beneath the slot (all looked intact with no cracking or other indications of a CSJ). I also didn't see anything else noteworthy on the board other than a few spots of minor oxidization which I cleaned off with a dilluted baking soda mixture and a dry cloth. Is there anything else I should be looking for or trying? It's driving me crazy that this thing is so close to working perfect, and yet not quite there.

 

Oh, and before I forget to mention it, I did try a Sega Card (F-16) and it worked just fine as well.

 

Thanks in advance for any and all help or advice on how to fix this one!

 

- Matt W.

Edited May 28, 2012 by gzsfrk

[bust3dstr8]

_{Check the last couple high addresses for continuity with a meter. Follow the trace back to the first component and check from there to the top of the cart slot.}

_{If you have access to a logic probe you can check the high address of the Rom chips themselves.}