Andy wrote: "Lastly, as I have no OPT, could I use two big arse resistors as loads for the EL34 OP stage? The OPT pri Z should be 1900 ohms, could I use to girt big 1k resistors as temporary loads?"
Try not to confuse impedance with resistance, the primary impedance of the transformer is governed by the turns ratio and the secondary load impedance, the primary's resistance is in effect constant no matter what and will be considerably lower than the primarys impedance.
If you a used a resistor(s) to the value of the transformers primary impedance then that would mean that at maximum anode current the anode voltage will probably be considerably lower than the screen voltage which could lead to excessive screen grid dissipation.
If you just want to connect something in the absence of the transformer so you can do a few basic voltage checks then guestimate what the primary DC resistance would be and use a resistor of that value, failing that connect the anode direct to HT.
But really you need an output transformer, if power measurement or full power test is your goal.
Lawrence.
Try not to confuse impedance with resistance, the primary impedance of the transformer is governed by the turns ratio and the secondary load impedance, the primary's resistance is in effect constant no matter what and will be considerably lower than the primarys impedance.
If you a used a resistor(s) to the value of the transformers primary impedance then that would mean that at maximum anode current the anode voltage will probably be considerably lower than the screen voltage which could lead to excessive screen grid dissipation.
If you just want to connect something in the absence of the transformer so you can do a few basic voltage checks then guestimate what the primary DC resistance would be and use a resistor of that value, failing that connect the anode direct to HT.
But really you need an output transformer, if power measurement or full power test is your goal.
Lawrence.
