https://www.radiomuseum.org/r/ultra_t671t_67.html
Look up the equivalents to the Mazda valves.
Any set with a similar lineup won't be much different.
I don't think it's in Trader sheets or R&TVS, though there may be a similar model. Check the index of service sheets here.
It's likely the first thing is to replace any paper dielectric capacitors (waxies, Hunts, Metalmite) before power is applied.