Mystery: Pokemon Yellow plays on GBC but not working GBA

[dako44]

I have just acquired Pokemon Yellow, and it does this exact thing. I have tested it out on an original GB and it did the same exact thing as well as on a GBA SP. I cleaned it, and it was a bit dusty but still nothing, and then I put a bit of paper underneath one side that looked like it was slanted down a little. I thought maybe that would help it make contact, but it didn't. After reading this forum the only other explanation I see is that the RAM may have gone bad. If so, how can I replace the RAM, or is it even possible to do so cheaply? Thanks!