Open heater on NOS tube

[glebert]

This is not an urgent question, but I'm curious anyway. I ordered a sextet of NOS Peavey branded KT88s a while ago when they were being sold super cheap. I wish I had bought a couple more, because one of them doesn't work. Heater pin reads open and it passes no current in an amp or my tube tester and never gets physically warm, unlike the other tubes. I'm sure the filament could have broken right away at the factory or sometime in the 20 years or more that they have been in storage, but I'm curious if it could be a bad solder joint to the pin itself (outside of the glass). Is there any point to trying to reflow the solder at the tube pins? I do have one project amp that takes a quad of KT88s, but otherwise having a pentet of big bottle tubes is just a sad pile of glass.

[Randall]

I have successfully reflowed solder in tube pins before. But, in my case, it was visible there was an abnormality at the end of the pin in question. In your case, why not? It couldn't hurt.

[g1]

Worth a try. The earlier Svetlana EL34's had a run with that problem. Usually resoldering them solved it. Sometimes it would not hold up. I think in those cases the solder was not sticking to the heater leads, similar to what can sometimes happen with NOS components.

[Enzo]

BY all means resolder the heater pins. Look into the end of the pins to see if either appears to lack connection. I have done that many times to octal pins over the years.

[J M Fahey]

That.

And you donīt have an incomplet sextet, you have a quartet with a spare