This is a lot of 12 NOS Russian "Mig" Fighter Jet lore, 6C33C output tubes as used in BAT, Joule, Tenor, and Ayon, Atmosphere Novatron amplifiers and others. I've had these tubes in storage, not sure if they are Svetlana factory for sure though they are only made in Russia, sealed in the original box, just as I bought them from my supplier 15 years ago. A letter inside says:
"The tubes are new old stock, and they are new tubes. I tested each one of the tubes, and they all test very close to each other, also as the others I have sold recently. The factory purple stamps on the glass is proof that they are not used. The purple stamps on the glass fades to a brown color, after some hours of use. If you look at your old tubes, you will notice the stamping on the glass is either faded, or not even noticeable anymore, due to many ours of heat to the glass. The stamping on the glass of the new tubes are still fresh purple on top and on the sides. These tubes were in test for 1 hour each. 15 minutes for filament warm up, and about 45 minutes with power applied. Some dust may be on the tubes because I had them stored on the shelf in the basement, and the boxes were not sealed. I assure you, that these are new tubes. As far as the tops of the tubes are concerned, some production runs of these tubes do not all have the silver shine on top. Some may have the silver shine, and some dark on top. The top internal coating is what is called the getter. It is a flashing process at the time the tubes are made. The purpose of the getter in the tube, is to absorb any oxygen that may be still in the tube, after the tube has been vacuum sealed. The top color of the tubes don't change with usage. That would take an extreme amout of heat, much greater than what the tube can produce. I hope that helps. As far as checking the old tubes, they really need to be electrically tested. You cannot really tell if a tube is weak visually. It has to be tested with high voltage/high current regulated power supplies with digital meters for voltage and current, plus a bias circuit, to test the tubes emissions accurately, which is how I test each one. Old tubes don't change, as far as their looks. The glass is so thick, that they stay clear, no matter how old they are. This type of Russian military tube has been discontinued 24 years ago, and are hard to get. There are other manufacturers for 6C33CB tubes, but they are not reliable, or test close in emissions to each other. I bought these tubes from a tube dealer years ago. He took trips to Russia, and brought them here, a hundred at a time. I bought many of these tubes from him, to have stock on them for my BAT amps. I still have a few sets left. If you plan to have amps using these tubes for a long time, would be good to have an extra set of tubes for the future. "
Bulk sale of these 12 tubes @ $40 ea. is a bargain as they are no longer available in this quality. Shipping to conus is flat $20. Please check my other listings & feedback to know that this will be an easy and quick transaction. truman/Atlanta