I have an old simple tube tester that you set the controls according to the type of tube, push a button and it's meter rates the tube on a scale, basically good or replace. Not a real good tester. But I've noticed that some brand new tubes that I've used and tested show that they should be replaced! They still work and sound ok but the tester says they should be replaced! I'm just wondering if others with a tube tester have found brand new tubes that work, but test bad? Yes Blue Strat, this means you!