[morzh]

Well, I was right about the pentagrid.
I received the one that I bought on the eBay.
First I repeated the experiment opnce more where I could not get the generator tone below 7MHz.
Then I replaced the pentagrid and I was able to receive the tone on the correct frequencies all the way down to 5MHz.
Scope also showed the oscilaltion all the way down, though really small aplitude.

I was also able to receive some stations down in that region. More than one, I think three.
Interesting is that with the old pentagrid, when I put it back, I was able to hear one of thopse stations. Also interesting that at least in some of the "dead" region I was able to receive the tone but instead opf going from the 7MHz down on the generator I would have to go in the opposite direction.

Last thing is, the tube was listed as NOS. It did not come with the original packaging.
The chart for Hickok shows 1000 for pentode and 300 for oscillator.
This tube shows 700 and 330.
My old tube shows 750 and 350.

So I wonder: is this thing (although working) really NOS?

Does anyone have data for 6A7 or 6A8? (they are more or less the same for Hickok measurements).


UPDATE:

I went back to the Hickok and checked the new tube on English: it is right in between Bad and Good. on the Question mark.
I also found a 6A8 that I replaced (it was working though) because id did show about 650 and it was also borderline bad on English.

Also by looking at the tube I think the soldering on top the Grid cap has been redone and then polished off - it looks as if it was smoothed with grit paper.

Well, maybe for 5 bucks it is not a bad tube but then the auction was for an NOS.

Let me talk to this guy first.