For having two types of output connectors you don't have to modify the BOM. How many VA depends on how much output current you plan to feed in loads.
The transformer has not to be overheated in case of prolonged 4A total, so 60VA. You also have to consider proper sinking for the main transistor if that will be the prolonged loading situation.
I'm using two L adapters to power the DCG3 ,+/-17V.
What is the maximum A.C input voltage for L adapters?
I asked because I have a pulled R core transformer 2X30V.
What is the maximum A.C input voltage for L adapters?
I asked because I have a pulled R core transformer 2X30V.
Max AC input is for as much rectified + ripple DC level as the reservoir capacitors allow before raw DC - Vref DC exceeds the 40V LM334 max spec. The bridge diodes usually have very high PIV unless they are low PIV Schottky. The real concern is the extra heat on the pass transistor that is going to be created by too much a DC in - DC out difference. The more current hungry the load the more Watt to sink in combination with the more voltage across the L-Adapter. At least with the DCG3 as a load you know what to expect and plan for as most of its consumption is its constant current output stage bias.
Thanks Salas!
I know about the high dissipation in the pass transistor but amn't shure if correct understand the raw DC- VrefDC.
As the expected rectified voltage is about 42v ,is it safe for lm334?Or the peak voltage must be taken in account?
We always speaking about the DCG3 as a load..
Vref voltage in this design is Vout minus Q1 Vbe. So the difference across the LM334 in your case is lets say 42V - 16.4V when all voltages have settled. But there is a ramp up mS time also until Vout charges to programmed level. So maybe precarious. See posts #35 and #70 as well.