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Forum Index : Electronics : LM723 30V-10A Power Supply Problem
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Yes i expect you do know how to connect a tranistor, i would like to see what heat sink you have the transistors attached to. I also dont know your soldering skills and would like to see a photo of the solder side of the board. There is a circuit fault, we need to find it, so good clear photos might help me. Sometimes it just works |
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| novosyst Newbie  Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Your photos are not very clear and when i zoom in all becomes blury, i am unable to see the solder side clear to check your circuit. The bridge rectifier looks a little small and needs a big heatsink. Your soldering looks neat from what i am able to see, but again the photos are too small to see clearly. The 5w resistors will get very hot, so they might need to be spaced above the board to allow better cooling, or they will cook the board over time. Pete. Sometimes it just works |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
Pete - bridge is 1000v 25a and not hot during work , resistors are not so hot too , and i have common fan inside the box ))))) foto is good but i cant sent they because server has 1000k limit and i dont understand how i can do it good for you best regards Paul |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
Hello,maybe we can find an error on this figure )))) 
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Your schematic is not that easy to follow, but its a good attempt to help solve the problem, and i think i can understand it. From what i think you have done according to your schematic, is you have Collector and Emitter reversed in the circuit for Q1-Q4 (3055), the collector (C) should be wired to the voltage supply in, and the Emitter (E) should be wired to the 0.1R resistors, please double check your circuit to see if you have these wired backwards. Pete. Sometimes it just works |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
Pete i dont understand you -i have collectors on common + after bridge and emitters to each of 1om 5w resistors.whats the problem you see. pavel |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Your schematic is a little Chinese in the method of how you have drawn it, and i had misunderstood it, it do look like you have it correct. Its late here and bed time now, so i will have another look tomorrow and see if i can spot a problem. Pete. Sometimes it just works |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Have you checked if the 5K pot or the 500R pot are working correctly and are not damaged. Pete. Sometimes it just works |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
dear Pete -honestly do not understand how a potentiometer can affect the current through the transistor., I come to the conclusion that this scheme provides a basic mistake and work can not in principle.look at this please http://www.diagram.com.ua/list/power/power487.shtml but pots are good |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
In many ways it is almost the same circuit design, other than its a fixed voltage supply and the voltage can not be adjusted. The simple fact the circuit design i posted do work and there is many people who has built it and it work for them, the owner of this forum Gizmo, built it to the posted circuit design and it worked for him to. That tells me you have a fault in your circuit build, or perhaps a component has failed like a Pot. The pots are used as voltage dividers to set a trip point to control the output voltage or the current limit. If for some reason the pot has a fault or been damaged then output voltage can not be adjusted. This is why i say test the pots, its a simple resistance test with a multimeter. Pete. Sometimes it just works |
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bfgstew Newbie Joined: 27/04/2013 Location: United KingdomPosts: 19 |
Just completed building my supply as per Petes schematic and it works. Novosyst, please take note of what Pete is saying, the supply works as it is, you must have done something wrong somewhere, or you have a faulty component. Check you wiring, post high quality photos so the guys here can help you. Red to red, black to black and blue to bits! |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
ok guys, I have laid out the assembly. its a universal circuit board. I painted the track and location of elements. it is easy to understand where is my error.look and help me .and tell me please why you are using r7 1kom . |
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| bfgstew Newbie Joined: 27/04/2013 Location: United KingdomPosts: 19 |
R7 is 330R, not 1K.............? Do you get a voltage output? If so, can you vary the output? Red to red, black to black and blue to bits! |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
And there, most likely, lays your problem. You may be better off to use veroboard for the IC & small components and use tagstrips for the transistors & resistors that will get hot. "Painted" circuits are not a good way to obtain a reliable operation of this power supply. BTW, I too have built this power supply and it works very well. Klaus |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
sorry r8 , yes a have voltage output |
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| bfgstew Newbie Joined: 27/04/2013 Location: United KingdomPosts: 19 |
OK, you have voltage output, can you vary the output using the 5K pot? Red to red, black to black and blue to bits! |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
yes i can , but if i have short outputs , and begin vary current i have 3055 damage. |
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| bfgstew Newbie Joined: 27/04/2013 Location: United KingdomPosts: 19 |
Well if that is happening may I suggest you double check your circuit, use a magnifying glass to make sure no stray strands of copper wire are touching ground or other parts of the circuit, as you have voltage and you can vary it suggests that most of the circuit is working. As you can read, others have built this supply and IT WORKS, it must be a fault with YOUR CIRCUIT. Have you checked the output current using a multimeter correctly to see if it is working, rather than shorting the outputs out? Red to red, black to black and blue to bits! |
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| novosyst Newbie Joined: 24/11/2013 Location: Czech RepublicPosts: 16 |
OK ,on the third page is layout elements on DIY PCB. can you check the correctness of assembly. I can did a basic mistake when soldering. its the usual DIY PCB ,copper tracks I drew. |
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