This site ChipDatasheet.com is a reference for electronic components, here you will find verified information about the specifications of transistors, resistors, diodes, capacitors, ICs ,as well as datasheet from manufacturers. There is also a pinout of contacts and diagrams for switching on devices. In the equivalents section, you can choose a suitable transistor or any other element to replace the failed one. If you need to find the Datasheet, then this can be done easily using the search on the site.
Vacuum Tube: 12AX7.