Hi folks,Just wondering,is it possible for a "new"(NOS)tube to have heater to cathode leakage.I was under the impression that this was a problem that may plague a tube after years of service.I replaced the 6SQ7 in my radio because it failed all of the merit tests on my Eico 667 and it was the only tube in the radio that hadn't been replaced,so I decided to make a clean sweep.I ordered the new tube and when I got it, I tested it.According to my tester,it has a fair amount of H/K leakage.I put the old tube back in the tester and as I noted before,no leakage but low merit tests.I have suspected in the past that this tube dealer has sold me used tubes in place of new;are there any grounds here to support my suspicions?Is there something else that can cause this problem in a NOS tube? Thanx.

This particular tube is often under such a low load that its being weak will have little or no affect on its performance.

Regarding heater to cathode leakage, that is another story, and, depending on how the cathode is wired, may or may not cause hum in the audio. If you don't have hum, and the heater isn't glowing abnormally bright, then you should be alright. If a short occurs, and the cathode is connected directly to B- (as is part of the filament circuit), the filament will glow brightly. This may burn out either the filament or the cathode fuse (thin strip that connects the cathode to the lead-in wire). If the fuse blows, you'll get hum. In most cases, though, with the way this tube is normally wired, if you don't have trouble now, you shouldn't be too concerned with using the tube. If trouble does show up in the future, it won't likely damage the set.

T.