TooExpensive

Hi again, now I understand the question about the transformer: Without mod.: free: 26,33V loaded circuit with 25V preset/4,3Ohm: 25,7V modded: free: 28,96V loaded: 28,3V I got these values from my records and I could also read the Voltage after the rectifier/smoothing sinks on the big transformer from 37,8V to 34,4V. Should I think about shottky rectifier? Or will thicker wires do the trick...Ill see. In the original thread the BD249 for output transistor is mentioned...is this usable...are modifications needed to do this? Bye again.

Hi, I can measure the output disortion, what I did was after my mind to determin the point when the circuit becomes instable or the supply voltage drops too much. When I set the potentiometers beyond this point when driving low resistance loads it shows in form of fast growing spikes on the screen which also shows in dc setting. Of course I cant get this resolution in dc. I cant say how much the output voltage drops at 25V/5A because i didnt measure it yet, but I can say for 30V preset at 4,3Ohms. I measured 6,25A and the clamp voltage dropped to 27,8V. I try to keep that in mind to measure it. Sure it is an important stability point. Can you repeat the question about the transformer please in other words, my english is not good enough to give you the right answer. Bye for now.

Hi, 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 :) . 25Vpsu.rar

Thank you for your fast reply, I have all missing parts together now (mostly high power resistors). Except the OPamps MC34072 was not in stock the other n/a. Ill figure out about this problem later. Tomorrow will be a corrosive day (hopefully). Ill keep you updated (maybe with some pictures from my 640x480 webcam, who knows...) Good night.

Hi there, I have researched a bit and found this project worth building, it is of usable quality and as a big plus the layout is available so Ill just give it a try. Since I have a 24V/210VA transformer available this is my starting point. I want to use the layout of the original project of course with the benefits of higher output current. U1-3 will stay TL081, I have them already. 3x 2N3055, each with emitter resistors of 0,1R-0,27R/min. 2W (all will get the same value). Q1/Q2 will be TIP31A or BD241 depending what I can find in my boxes or what is available at the store. If I got it right the absolute max. current is despite the power dropped over the output transistors depending on the voltage over R7 which is 1,41V (I hope I remember this value right?!) for full current limit with current potentiometer set to max. current? My simple mind says: lets drop R7, add another 2N3055 and get more current safely. I know this will most likely not work out...why...an even better: can it be done and how can it be done? Anyways for the parts consider the parts list here:

Hi, this is my first post here, so please dont eat or beat me. I WAS willing to build either the oiginal or the improved PSU. I even bought some parts for the project today. But after coming home i made the mistake reading the two threats. The one for the original design with incredible 78 pages and this one with 22. A huge input and an outstanding example of endurance. Good work, especially by kain and audioguru. This runs for 2 years and still postings are comming in this proves the interest in this circuit. But after reading all this i am missing a summary. It seems that the double sided layout works out very fine. Maybe the autors can add it to the original projects page to make it easier building it. I find it very confusing to search every bit of information from the posts. Maybe some member could post the recent parts list/schematics/layout? Bye, keep it going!