How much current (mA, amps) does my PT need to be rated for?
You need to determine this for each of the secondaries. For the high voltage secondary, power tubes are the most important factors. You’ll have to estimate the peak current draw per tube plate and screen and multiple by the number of tubes. For a single 6BQ5/EL84, the max. plate current is supposed to be 65mA, and the screen is typically 5mA or less, but throw in a few mA for good measure, call it 75mA. (You can get this from the spec sheets). For two 6BQ5s in Class A, double that. For Class AB, the average current is the same, but the instantaneous current is higher, depending on how far toward Class B you bias. At Class B, you’d need a secondary capable of double the Class A current. Now add current for each of the other tube sections. Each half of a 12AX7 typically pulls around 1mA, but could pull up to 3mA. If you aren’t sure, use 3mA per triode. BUT… if there is any chance you or someone else would ever substitute in a 12AT7 or 12AU7, you’d best figure 10mA or 20mA max per triod
