as promised I want to post the fruit(s) of my efforts. Thanks again to everybody in the front lines for developing the circuit to this state.
The image quality is very low but its the best I can offer, therefore I have not tried to make an image of the scope line when testing the circuit.
Please keep in mind that its an experimental arrangement for testing purposes.
While building the board I noticed that the board layout is in some places a little unsuitable for this circuit, its very tight and the main conductor pathes are a bit small, but nothing serious. There is always a soltion.
The main facts: The values are always checked by oscilloscope/AC/0,1V-div/2ms-div to get no measurable disortion at the output clamps while driving my selfmade restistor network (pic.5)
Smoothened by 22000uF extern plus 4700uF on board.
Transformer ratings: 630VA 2x29,4V running free (original 1x26,3V off two paralleled windings to which I added 3 turns each)
The smaller transformer on pic.4 is 250VA 1x24V for the first tests but I want to have two outputs.
I exchanged the opamps to LM741 which runs at its supply voltage limits but nothing gets warmer than it shoulds an everything is stable.
What do I get for my money: max Volt out without load: 32,4V
Shortened output current at max. Volts and max. current: 8,3A
Maximum stable output Voltage with 4,3 Ohms attached while turning the Volt. Pot. up and the Curr. Pot. set to max. 27,6V pure flatness on the scope line at given settings while current rises to 6,2A.
Voltage set to 30V without load and turning up the current under load gives 6,25A and the clamp voltage drops to 27,8V again flatline on the scope.
R7 is two paralleled 0,47Ohms/5W but will be exchanges against 0,22Ohms/20W, they get very hot.
Of course bigger heatsink for the output transistors are needed, but its just the testsetup.
Alltogether I hope you will agree to the rating 25V/6A which was my target. It could deliver more by lifting the transformer voltage and using better rated opamps, maybe worth a thought.
Bye for now, and dont fry much power resistors.
PS: on the first test R16 smoked a bit because I exchanged Base with Emitter on one 2N3055 but nothing happened to the rest of the circuit. Man, I hate mounting TO-3 in the late evening hours