You may have heard of US plans to install an antimissile system in Europe. Talk is going round about locating radars and missiles in Poland. Naturally the Russians are unhappy about an American mini-star wars anti missile system right on their border. After huffing and puffing for a while, Putin made a counter offer of access to a Russian anti missile radar in Azerbaijan. He must have figured it's better to Americans snooping around inside a Russian radar site than have the Americans setting up their own radars.
Putin recently allowed a team of Americans into the Azerbaijan site to assess it's suitability. The Americans were not impressed. The 1985 radar runs on vacuum tubes. This is a big step backwards. In 1973 I designed sections of the American ABM radar and it was all solid state, not a tube to be seen. To learn that the Russians were still using vacuum tubes 12 years later indicates that Russian cold war technology was neolithic.
The basic problem with vacuum tubes is they burn out, rapidly, like light bulbs, for the same reasons (hot filament eventually fails). Tube reliability was so bad that 1960's USAF aircraft required replacement of the UHF voice radio after merely four missions. The solid state radios in later aircraft would last forever. Going to solid state, from vacuum tubes changed a flaky unreliable device into something that lasted the life of the plane. A UHF voice radio is pretty simple compared to a radar. The real reason the Azerbaijan radar used tubes has gotta be that the Russians couldn't make decent transistors as late as 1985. The article didn't say what the mean time between fail (MTBF), and mean time to repair (MTTR) is on that radar, but it's gotta be horrible.
The Russians made the excuse that vacuum tubes could better withstand the electro-magnetic pulse (EMP) from the detonation of nuclear weapons. Right. When the EMP is strong enough to damage transistors, the blast has already leveled the place.