How to fix the "stripey graphics"
As mentioned above, faint vertical stripes are visible on the Tri-Star's
picture. These are quite noticeable, especially when playing a game that scrolls horizontally, such as Super Mario Bros. Nintendo's own top-loading NES consoles have this problem too.
This problem can be easily fixed. If you open up your Tri-Star and take the top off, you will see there is space for a capacitor behind and to the left of the Famicom slot; a circle with a + sign is printed on the board there.
Buy a 1000uF electrolytic capacitor (rated at 6.3V or above; I used a 50V one). There is a fair amount of space inside the case, so it doesn't have to be very small. You can get one from Tandy/Radio Shack or any electronics supplier; it should not cost much.
Using desoldering braid and a soldering iron, remove the solder that is
blocking the two holes inside the circle. Insert the capacitor, making sure the positive terminal is in the hole towards the rear of the board (where the + sign is printed), and the negative terminal is in the other hole, nearer the front of the board. Push the capacitor down close to the circuit board so most of its legs are through the other side.
Carefully solder the two legs of the capacitor on the underside of the board, and cut off any excess wire. That's it! Put the Tri-Star back together and test it out. Enjoy your stripe-free picture.