There are also testers in carry-cases.
And there are companies that sell tube amp kits with very detailed instructions, some based on the Dynaco specs and designs from the 50s-70s. Repro parts are still made. Dynaco sold Dynakits back then.
The tubes are mostly Chinese or Russian made, possibly some in Ukraine.
Thing to remember is they run very high voltages and they can self destruct when one’s back is turned.
This vendor has been around for decades and has a supporr forum… http://tubes4hifi.com/
Of course…