Open your own Nintendo repair center with these

Back in the NES era, Nintendo had official World Class service centers. These repair shops had a couple of yellow cartridges that ran diagnostic programs on a damaged NES. Unfortunately, if a NES suffered from blinking light syndrome the carts were rendered useless, since the cure for fixing the irritating flashing red light is replacing the 72 pin connector. Even though the cartridges are largely useless (except for the joystick test at the end) many collectors want them because they were not released to the general public. On eBay one seller grabbed a bunch of these including an even rarer Legend of Zelda NTF2 cart for $850. A hefty price to play Dr. Nintendo, but you could open your own Nintendo World Class service system to pay the eBay bill.