Hi Pete, The Torsk Volunteer Association has been restoring the Radio Room aboard the USS Torsk (SS-423) for many years now. Vacuum tubes are readily available, not always cheap, but available. Parts is the big problem, especially filament transformers. Our Radio Room has an R-390A, a AN/SRR-13A, AN/URR-13A, AN/WRR-3, an RBS and a host of support equipment up and running. Our TCS-12 transmitter/receiver has power supply issues requiring a new transformer, and our URC-32 transmitter/receiver has tuner issues requiring a new belt and total re-alignment. Keeping everything in repair and good working order could be a full time job. Since it is not, equipment that breaks is usually down for a while. We do have fun in a sadistic kind of way.