Tung-Sol 5881 - Hard, Medium, Soft?

[Audiotexan]

The photos of the two versions of 6L6 that AudioTexan posted are good examples of multiple versions of a single tube design. The top one is the same tube guts of a 6П3с-е that in the Soviet era was always the wafer base. When rebranders started using it they sold it as various tube types and later added the full base and a short plastic base so tube clamps would work. The internals were the same.

So if I'm following correctly, then what I've got here should be accurate:
(correct as needed of course)

The point was that they were built to pass a spec that was required and circuits were designed around that spec...

Makes sense. I guess where I got lost/confused was generally speaking (and this should address my blue-prints reference/nit-pick): When a set of blue-prints was drawn up here, it was shared within the "same family". That meant, the "secondary manufacturer built that tube in the same fashion (meaning plate cuts/winding style/etc.) Because they were using the same blue-print.

EG: The tube would look the same whether GE made it in Owensborough, Kentucky, or in Tell City, Indiana.

I was thinking that since you said "they all had the same blue prints", they should all look the same.

Rather then, when you spoke of blue-prints, you meant specs instead. Not the actual tube design. Huge difference (at least for me).

So, now that I'm on the same page hopefully...(and thank you for expounding on what you were trying to get across!)

All of my 6П3с-е have the two oval cooling holes but I have seen them with different plate stamping, different getter location and different plate finish. It is also common to see them with hardly any heater visible and others where it is sticking up to 1/4" above the cathode tube. Any they all work essentially the same and came from different plants. The variations are local to particular plants and the one thing they all had in common was exceeding the specs printed for them

Thanks for the additional pointers to look for! I definitely would not have thought there to be such a wide variance in manufacturing styles (especially plate-stamping) from the "same blueprints". (Version revisions notwithstanding)

The lower tube is not a 6П3с, those had no cooling holes but came in mostly large black plastic bases, which also do not fit many clamps in the west because the bases are wider. These are also rated at 250vdc and are reliable to 350 or pushing it to 400. I refer to them as super rugged 6V6 because the worked in the Jim Kelly amps which would kill any other 6V6 in the land.

So, now that we know that the below "6l6-5881 Sovtek WXT-Plus" pictured below is NOT 6П3с (Big thanks g-one for the real pic!, and Stan for confirming)..nor 6П3с-e, any idea what the true type (Soviet designation) is for this??






I guess we can expect the same "variances" from the "5881 reissues" if more of the 11 plants start making them... /nightmare to keep up with

Given all of what I've learned in this thread... I may just opt to stick to continuing to learning to ID strictly vintage tubes. That's a tough enough goal, but at least *that's* accomplishable. LOL