Mike H wrote:For the low current one, maybe it's cathode has been stripped?
I agree. It was a long time ago when I bought all my 813's second hand off eBay. A large percentage wer plain worn out, even though they looked like new. I did make plenty of noise about it at the time. Just as I made plenty of noise about the condition 212's get into. In the case of 212's it was a much more painful problem to the finances. I think my average price was £250 for used ones, and when you devide it up by the ones which transpired to be old cripples the cost to me for each one I now own that works at all must be £500.
It is a strange thing about the interweb that people write all these wanderful websites with great graphics great write up on their circuit and ulogies about their wonderful amp but nobody else seems to mention all these pitfalls.
The 211's I own have done me a much greater service, the GM70's are bullet proof, and I have no doubt the GK71 likewise, because we know that those are genuin NOS, only because of the huge amount of surplus from the Russian sector, there is no value attached so not worth touting worn out ex transmitting valves on the second hand market.
the problem with the 212's is the man looking for them is like a man looking for hens teeth. the listing only ever says there is filament continuity but can't test the valve. You only need one other bidder as keen as mustard and the two of you have made yourself pay silly money for a wore out ex transmitting valve which was removed due to it no longer being effective.
Oh to go back with this head on those shoulders.
Was it worth it? No. But i am older stronger and wiser through the experience.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein