I am would like to get the Calibration data in order to test the DC points for all the unit (the DCvoltage for 0 volts ac signal), the mA of current flowing for the tubes (Q point of them!) accordint to the design and any notes of the manufacture or DIY for verification process, I won't like to fry a transformer!!
BTW: did you finish your U273 project?, few years ago I contacted for.