Russia imposed a ban on the export of *all* tubes. It is news to me US companies are still making tubes. The last I read, the only exemptions are health care manufactures, health care companies and drug makers. Russia specifically banned the export of vacuum tubes. Electro-Harmonix, which distributed Soviet tubes announced earlier this year that they could no longer supply Soviet tubes due to the ban
https://www.guitarworld.com/news/electro-harmonix-russia-tube-exports-ban