I used to walk down to the local Shack as a kid to use their tube tester and buy tubes if needed. I would purchase the Realistic LifeTime guaranteed tubes. They were guaranteed forever (just bring your receipt and tube back to the store). yeah right. Now my older brother, get this, still has original receipts from the 70's for the LifeTime tubes. They still honor the guarantee too. not sure how but they do. My favorite electronic place was a place called weiderman. it was like a bulk foods store but instead of gummy bears in the bins it was pots, and caps, and resisters.