TI-99/4A Cartridge Lifespan

Hi, I managed to get at least of the necessary pieces to have a usable TI-99/4a although I think I've don't have the proper pieces for video, since all I get is B&W. I'm wondering why of the six cartridges I've got three work just fine. Two don't work at all, and one "Parsec" works if I fiddle with the tuner on the TV after it's running, yet the initial screen that lets you choose BASIC, or the game is normal. Is this a indication of dead carts or a problem with my computer? What is the estimated lifespan of the standard cartridge, and how can environmental conditions effect this? Thanks, Zane | Zane H. Healy | UNIX Systems Adminstrator | | healyzh(a)ix.netcom.com (primary) | Linux Enthusiast | | healyzh(a)holonet.net (alternate) | Mac Programmer | +----------------------------------+---------------------------+ | For Empire of the Petal Throne, and Traveller Role Playing | | see http://www.dragonfire.net/~healyzh/ |