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Tintin last won the day on January 9 2021

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  1. I, I had the same problem of you. To fix it, make a minimum load with resistor. For me a 25mA load was the minimum to decrease this. See there :
  2. Hi, as promised I made an English translation of my working. Maybe there is few mistakes and I am sorry for that ! Good reading. ExplicationEN.pdf
  3. Hi, I just finish my power supply ! I made a PDF document (with a lot of picture and explanation) who resume all the story about this adventure, and made a lot of measurment ! It is in French but I will translate in English soon. I thank all this community, who made a great job ! I join you some photos and my work on a PDF format. Alimentation0_30V.pdf
  4. Hi Audioguru, Sorry I do not understand your last phrase " The opamp used for U3 and the negative supply voltage must be allow the output of U3 to go low enough so that the input to the output amplifier is shorted to 0V when the output of the project is shorted. Then R7 is the load. " If my memories are good, if I make a short-circuit when the POT2 is set to zéro, the Voltage output do not go down to 0V, and when I turn clockwise the POT2 the current go up. But I remember with this method, I have 3 A maximum wioth POT2 set to the middle, or if I put a load for 3A the POT 3 need to be max for 3A max. This is this difference who make me perplexed ! PS : I buy a new toroïdal 28VAC 160VA ! https://www.tme.eu/fr/details/tst150w_28v/transformateurs-toroidaux/indel/tst160013/
  5. Ok finally I test limited current and the voltage above R7 with 500mA is 165mV and 313.8mV with 1A. I measure with milliohmeter and I have 430mR for R7. I don't understand why the voltage drop is not 0.43*0.5=215mV and 0.43*1=430mV ? So I make some test : a) For max 3A output with Pot2 max I have to put 1.304V on U3+ b)It's works fine, if a put a 3.01A load (with my electronic load) the Led bright and the current limiter est working. c) But I test to make a short-circuit I blow up my primary fuse (630mA T, maybe to low). Why do you think about the voltage drop about R7 and for my 1.3V for 3A max ?
  6. I find the problem of the fallen voltage, it is due to a Fucking wire like this who have a 2.8 ohms resistor : So I can test now the current limiter function correctly !
  7. If my theory is good, the wire between output and banana plug have a resistance of 2.82R. How to calcul it : R1=U*R2/U2 - R2 R1=5V*10R/3.90V-10R=2.82R. That explain : a) why the chinese voltemeter "see" 5V and not 3.90V after bananaplug why with 10R load for 5V =>3.90V at output for 8V = >6.90V output for 10V =>7.50V output c) why, when i test with my electronic load, with 100mA on my electronic load I have a current of 282mA ! This evening I try to measure the resistor of the wire, I will change it tomorrow.
  8. Oh I measure without my my chineese multimeter and so I have 3.90V on the 10R charge load. I decided to measure voltage directly on the output of the PCB and surprise I have 5V ! So I think It was the cable between the negative output and the banana-plug who make this voltage fall ! Sorry for this disturbance, I will say you if this is it or not !
  9. So I make my measure and this is result : 1) If a have no load (D is my ground) : -UR7 (U_CD )= -12.6mV -U_AC= 0.745V with RV3 set to 100K -U_AC=2.47V with RV3 set to 0K -U_BD=11.7mV -U_BC= 24.8mV (11.7-(-12.6)) If I put a 10R load for 5V to output : -UR7=-115mV, so I=0.115/0.47=245mA -U_AC = 0.635V with RV3 set to 100K -U_BD = 11.7mV -U_BD= 128mV
  10. Ok thanks Audioguru for your explanation, I wil take measure but I have one questions : When you write on shematic +1.41V above R21, it is between Circuit OV, not the output ? I wonder if the ground have to be before or after R7 ? Is there any importance ?
  11. Hi, I made a lot of test yesterday and it's works fine, i.e it could deliver 3A <20V, 2.5A<24V and 1A to 30V. It's ok for me, I thinks what did you say and maybe I will buy a 28VAC 160VA toroïdal transformer. So I test for ripple voltage for 5V 1-2-3A, and it was pretty good. I test start and my "disable output" and the results were good, particularly the limitation of current peak. Well finally I test de current limit function, and, after adjusting trimmer RV3 for 1.41V (max 3A), when I make a short-circuit with the Potentiometer 10K at full the current go up to 6A and it blows up my primary fuse (630mA). 1)Ok, I replace the fuse, and I wonder why the max current is 6A ! 2)So I test to 5V with a 10R Power Resistor, and, instead of having 5V500mA on my Chineese Multimeter like this : https://fr.aliexpress.com/item/Digital-DC-200V-0-10A-Red-Blue-LED-Dual-Display-Voltage-Current-Meter-Voltmeter-Ammeter-Power/32605098792.html?spm=a2g0s.9042311.0.0.L5o1rg I have this : 5V with 0.390mA... 3) I test with my multimeter and it is not 5V but 3.90V with 0.390mA ! 4)So I have 3 problems : a) Why with the pot2 to max and with RV3 for 1.41V or even to make it at fully (100K), the current limiter is over 6A ! b)Why now the voltage regulation go down with a small charge, go 5V=>3.90V with only a 10R Power resistor. It's the same with 10V=>7.5V and 8V=>6.90V for example. c)Why the chineese digital multimeter see 5V and not 3.90V ? I test with other and it was the same things. Or yesterday when i make test, when I put a 2A load on 30VDC the chineese meter saw the same fall than my Multimeter, so why now it did not see the voltage fall ? I Checked AOPs, Transistors and voltage on AOP, main capacitor, and all is fine. I give you my schematic and how the digital meter is plugged. Thanks
  12. Hi audioguru, You are right with the fact with 27VAV => 44VDC after bridge rectifier is not normal, even without a charge. My hypothesis is on my PCB : -we see the wrong side of the things : maybe it is not the V+ who go up to 44VDC but the V- who go down to -8VDC when there is no charge (or <20mA) between + and - of the bridge rectifier -and so, if my hypothesis was good, we have to find why and where is the new "zero point" -Maybe the rôle of the section D5-D6-C2-C3 is important : on simulation on LTspice, whe have a sinusoïdal voltage between -4V and -12V (so the mean is -8V !) between D6 and C3 on normal situation... My point of view is, even it's working well with a charge >25mA, I would want to know (because of my scientist brain) the cause of this fealure, in order to not make the same error the next time !
  13. Ok, finally I replace R1et R1-1 (1K+1K2) by two 2k2 1W in // and it's works very well. The first test are pretty good. If you want I made a final review when I will finish my Power supply . The odd things is the fact that the transformer need a small charge (not too small - 30mA) on PCB to works well and on Protoboard it not need a charge at all to make 36VDC... Thanks audioguru for your answer !
  14. Hi : I am not sure if you understand my problem : I measure Voltage on the PCB without AOPs and Transistor, to make sure all is ok before put the AOPs. The voltage I give is on The collector of TIP3055, just after the KBK. 1)My transformer is not cheap : I test him on breadboard with same main capacitor and Resistor, it give me with small charge 27VAC and 36VDC after bridge rectifier on BreadBOARD 2)I don't understand why on my PCB, I have 36VDC after bridge rectifier only with 1K resistor... With 2k2 or without resistor the voltage after bridge rectifier go up to 44VDC... 3) The question is why, with same component, I have a problem only on my PCB... Maybe a ground loop problem ? I checked many times all connections and all is fine, so...
  15. Hello, I make a PCB with this schematic, with a 24VAC transformer, who give normally 36VDC after main capacitor. I test my PCB without AOPs and Tmain transistor (BD139 and TIP3055) and I measure Voltage after main capacitor C1 : -The voltage start to 36VDC and grow up to 44VDC and stabilize. -After inspection, I remove R1 (in my schematic R1 1K+R1-1 1k2) and I have 36VDC, ok. -I put a 1K resistor for R1 (R1+R-1) and I have 36VDC for testing. -I put a 2k2 resistor for R1(R1+R-1) and I have 44VDC... -I I remove R1(R1+R-1) and I have 44VDC !!! -I replace 1K resistor and I have finally correct 36VDC... What is the explanation of this ? Thanks and sorry for my english.
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