Main meter, Bias meter, AC meter, Solid State Conversion, and many more.
Along the way William (Bill) eccher designed and fabricated the following modifications. A precision bridge assembly to replace the bridge spool resistors. A solid state conversion for the 5Y3GT and 83 type tubes. A passive line voltage meter calibrator that corrects meter error of +- 5 VACr. A plate current mod to measure the current without breaking the circuit. An internal 12 volt line bucking transformer to minimize the voltage drop across the power adjust rheostat. I also did some custom digital conversions of the bias and ac meters using more expensive meters that were available.
Voltage reducer used to drop the line voltage.
A little about the designer
Some bio and background on Bill Eccher