UC3842 Test Circuit _ Electronics Repair and Technology News

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UC 3842 Test C i r cu cui t | El ectr on oni cs cs R epai r And Technol ogy New s

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Home > Electroni Electronic c Project > UC3842 Test Circuit

UC3842 Test Circuit By Jestine Yong on on August 27, 2007 Like

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UC3842 IC can be easily found in most of the electronic equipment switching power supply. Normally whenever the power fet shorted, chances are very high that the uc3842 pulse width modulation (PWM) IC may shorted too. Although sometime you can use your meter to measure certain pins of this ic to confirm whether it works or not , i found it to be not accurate. I personally had tested some of the defective UC3842 IC where it tested good with meter but failed when on load (in circuit). In order to fully test this IC you may visit this website that talks about building your own UC3842 IC test circuit. Likes

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Manjunath September 14, 2009 at 5:43 pm

Can you please give me the circuit that generates Triggering Pulses to the power circuit using IC3842.? Likes

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admin September 14, 2009 at 7:51 pm

Hi Manju, Sorry i do not have such circuit. Jestine Likes

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Thomas April 22, 2 010 at 7:52 am

Hi Jestine, Do you have any switch mode power supply circuit using UC3843A ? Likes

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Noahtech Electronics … 841 likes

admin April 22, 2 010 at 8:59 am

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HI Thomas, Try this link:

Be the first of your friends to like this

http://electro-tech.narod.ru/schematics/power/comp/atx/sunny_atx230.gif Jestine Likes

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January 11 at 5:41am

syed July 23, 2010 at 12:03 pm

hi yong i "syed hussaini" is very glad to know that there is a community of elctronics repairers because i myself being an "ec eng" and would like to be apart of it as i am having more than 25 years of expereiance in this feild and been repairing many types of devices so it will be very useful site for me thank you Likes

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Noahtech Electronics Training added 5 new photos o the album: Electronics Repair Course.

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admin July 23, 2010 at 7:52 pm

HI Syed, Welcome to my blog and you can visit http://www.electronicrepairguide.com to become ERG member and it is free. Jestine Likes

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manjula October 6, 2010 at 3:19 am

power supply diagram using uc3842 ic Likes

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manjula October 6, 2010 at 3:22 am

please send me online 6kva circuit diagram Likes

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admin October 6, 2010 at 7:32 am

HI Manjula, Sorry i do not have such diagram. Jestine Likes

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admin October 6, 2010 at 7:33 am

HI Manjula, http://jestineyong.com/uc3842-test-circuit/

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Try here: http://www.alldatasheet.com/view.jsp?Searchword=UC3842 Jestine Likes

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imran November 26, 2010 at 11:31 am

give me induction hiting and furnas curcit camplit Likes

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admin November 29, 2010 at 8:43 pm

Hi Imran, Sorry i do not have such circuit. Jestine Likes

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rouie January 27, 2011 at 3:26 am

Hi, I bought something, its a electric carving pen, at first it was working fine, but after a day, something exploded inside, when I checked it, it was a uc3842 IC that exploded, can there be an explanation why did it exploded, a big chunk of it where the number was printed is the one that popped out.. and where can I buy this IC, and have it replaced.. Likes

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admin January 27, 2011 at 9:00 am

HI Rouie, There can be many reason why the power ic blown. It can be the design problem or the quality of the ic not good. This ic can be easily found in any electronics shop. Jestine Likes

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markos pachoyndakis February 11, 2011 at 5:19 am

very usefull thanks Likes

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laksh April 28, 2 011 at 1:22 am

i want the information about uc 3842 and also the circuit of the uc 3842 for the smps input 24vdc to 45vdc ,2amp. Likes

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admin April 28, 2 011 at 8:07 am

HI Laksh, Sorry i do not have those circuit. Jestine Likes

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alireza May 4, 2011 at 8:33 am

hi ,where i can find SMD components data sheets ? do you know any website that help me to find SMD datasheets ? tanks a lot ! Likes

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admin May 4, 2011 at 9:50 am

HI Alireza, Try: http://www.marsport.org.uk/smd/mainframe.htm Jestine Likes

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Alejandro flores gomez September 5, 2011 at 10:25 pm

for 10 year ago idont worked in electronic but now is a new opotunity to me to fix a very diferent equipment i dont remember mi englihs all the divices are very small Likes

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sebastiao evora July 20, 2012 at 2:49 pm

I want to know whether the more equivalent of this ic Likes

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Jestine Yong July 21, 2012 at 11:51 pm

Hi Sebastiao, Since this IC is easily get from the market thus you do need need to find the equivalent number. There are IP3842, HA17834, SG3842 and etc. Jestine Likes

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Alex Halter July 30, 2012 at 7:34 am

Hi, can 3842 be used as pwm speed controller for motors? And do you have any links on how to implement that? Your response will be highly appreciated. Thank you! Likes

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Jestine Yong July 30, 2012 at 10:04 pm

Hi Alex, Sorry no info on that. As far as i know they are mainly use in the power section or any circuit that requires a continuous pulse like in boost circuit. Jestine Likes

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oleg October 6, 2012 at 8:43 am

Excuse me for my bad English!!! I'll try to corrects some mistakes: Hi Jestine, I need somebody explains how the following power supply works: http://electrotech.narod.ru/schematics/power/comp/atx/sunny_atx230.gif I 'm troubleshooting a very similar atx power supply, exactly KY-500ATX model from MaxPower. 5 VSB and 5V ps-on are present, but ps wont start. There is no VCC (zero volt) at pin 7 of UC3842 PWM since 16-17V needed for pwm startup, neither VREF at pin 5. I also has been checked that IC Voltage supervisor activates a 5V Fault Protection Ouput (FPO) at pin3 and zero Volt PGO at pin 8 of LP-7510. What can be the problem? Why there is not VCC at UC3842? Why LP-7510 indicates a over/under voltage protection condition? (Shotky rectifiers at secondary seems to be ok and output filters too) How the ps-on circuit works? Please refers to http://electro-tech.narod.ru/schematics/power/comp/atx/sunny_atx230.gif for better understanding what i am talking about… Help me please!! best regards, Oleg. Likes

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Jestine Yong October 6, 2012 at 11:25 pm

Hi Oleg, PS ON will cause IC6 PIN 3 to go low thus causing the opto LED to conduct and this in turn will also cause the transistor in IC3 to conduct too. Once IC3 conducts Q2 also will conduct thus allowing supply voltage from D16 to pass through Q2 and turn on the power ic1 through the supply pin 7. This means you have to check all the components from IC6 till pin 7 of IC1. Sometimes if IC1 is shorted or leaky it can also pull down the supply voltage. Jestine http://www.JestineYong.com Likes

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Thanks you very much Jestine!!! I really high apreciate your answer because i am a beginner in electronic repairing. I took another identical working power supply and swapped a lot of main components one by one. Components extracted from failure power supply worked fine in the other. Also extracted components from the good working power supply were placed in the failure ps with no results, so we can say that the following components were tested and fine: IC1 (UC3842), IC2 e IC3 (Optos), IC6 (LP-7510), D16 (FR diode), Q1, Q2, T1, Tl431 and other small bipolar transistors in the secondary. After reading your message i will check also D3 and R41. I'm thinking that the power supply starts and inmediately stops by protects itself. Could be a bad secondary electrolitic capacitors? There are practically the unique components that i not tested yet. http://jestineyong.com/uc3842-test-circuit/

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I will try the D3, R41 and seciondary filters. Regards, Oleg. Likes

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Jestine Yong October 11, 2012 at 7:47 am

Hi Oleg, Yes it can be any component includes the electrolytic capacitor. The opto has to get signal from the ic otherwise the primary side ic will not function. Jestine Likes

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Hi Jestine! Definetively i need your SMPS repair ebook, but i have no way to buy it, i am a cuban engineer and here there is not way to pay online. Could you help me please with some free materials about atx power supply repair??? The materials i founded on the web are very basic troubleshootings techniques and not going deeper in other problems i founded on atx smps like regulation voltage problems, over or under voltage protection, to high standby voltage, etc, no drive signals on PWMs or supervisor, etc Please, help me with something you can. I'll really high appreciate it. Regards, Oleg. Likes

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Hi Oleg, You can use try use western union or money gram servicesor even bank transfer. As for the atx power supply repair you can try this link: http://www.repairfaq.org/sam/smpsfaq.htm Jestine Likes

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lee October 14, 2012 at 1:43 am

please..! Can you tell me about Verror of UC3842 ???thank Likes

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Jestine Yong October 15, 2012 at 1:42 am

Hi lee, Could you elaborate the meaning of verror? Jestine Likes

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Lee October 15, 2012 at 10:47 am

Verror-you search datasheet of IC UC 3842 ,it will help you show .! Do you have schematic buck-boost use Ic uc3842? I have a project : power converter in put : 9-19V use buck-boost converter with ic uc 3842 out put: 12V-4A Can you give me schematic buck-boost with ic uc 3842 ? Likes

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Hi Lee, Sorry i do not have buck boost schematic. Jestine Likes

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Hi Jesting! Thanks for the suggested link, but i already readed it. It is very useful link but no covers all the true cases i founded in the real world. Also thanks by suggestions on the ways to buy your ebook, but neither are suitables for me. Keep in mind that i need abut 3 months of working to complete thats money. Also Western Union here is to receive, not to send money. Thanks any way. Well, talking about my similar Sunny ATX-230 power supply the problems is that the output voltages are to high. I shorted the FPO 3rd pin of LP7510 to ground an then the PS started. When measured the output voltages were as following: 12V altered to 17V, 3,3V altered to 6,6 and 5V altered to 7V. That's the cause why PS start, then stops. Any idea? Any Suggestion? Thanks in advance, Oleg.

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Hi oleg, You can use bank transfer if you need the ebooks. In your case of high voltage check the components surrounding the secondary side of optoisolator IC especially resistor that will turn into high ohm. Jestine Likes

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