This SMPS Power Supply Has No OptoIsolator or TL431. How Does It Work? Switch Mode Repair

So Switch Mode Powers Supplies have an optoisolator circuit to monitor the output voltage tell the PWM when it needs to increase or decrease the drive to the Transformer. That is how the PSU maintains a constant output voltage while providing isolation between the mains and the low voltage side. But this little PSU doesn't have one. Yet it still regulates the output voltage. How does it do it? I work in collaboration with: The Electronics Channel (with Carlos and Detlef) https://www.youtube.com/@theelectronicschannel Gran Canaria Uncovered https://www.youtube.com/@GranCanariaUncovered (with Detlef and Julie. Not electronics related) Det Builds Stuff - https://www.youtube.com/@DetBuildsStuff (Detlef) Retro Upgrade - https://www.youtube.com/@RetroUpgrade (Carlos) For All Your PCB needs: free $5 discount coupon https://www.pcbway.com/setinvite.aspx?inviteid=561767 Equipment used in my videos. These are affiliate links, you pay the normal price and I make a small commission. TEST METERS ANENG AN8009 MULITIMETER https://s.click.aliexpress.com/e/_DDGumdd https://amzn.to/4da4Q7h https://amzn.to/4fsjkkm https://amzn.to/3yuf03q https://amzn.to/4fwQOOD https://www.banggood.com/custlink/KDDZhU2pBu KAIWEETS HT118E MULTIMETER https://s.click.aliexpress.com/e/_DcIhCiR https://amzn.to/3yC0ZRe https://amzn.to/3SHIEcy https://www.banggood.com/custlink/m3D9EzqcQR VC480C+ MILLIOHM METER https://s.click.aliexpress.com/e/_Dk0hlEx https://amzn.to/46Gg1Cm https://amzn.to/3YwUjyn MESR-100 ESR METER https://amzn.to/3yxQ0Zd https://amzn.to/3WSr73A https://s.click.aliexpress.com/e/_DCY5FT5 XC6013L CAPACITOR METER https://s.click.aliexpress.com/e/_DBmud5Z https://amzn.to/4cf2lzm https://amzn.to/4dw9cp5 TM-902C TEMPERATURE METER https://s.click.aliexpress.com/e/_DEXr4tz https://amzn.to/4fAz44L https://amzn.to/4fBxD69 LCR-T4 COMPONENT ANALYZER https://s.click.aliexpress.com/e/_DBEGAWX https://www.banggood.com/custlink/mvDSR2qHWq https://amzn.to/3X4rOHv https://amzn.to/3Agcj6h FNB58 USB ANALYZER https://s.click.aliexpress.com/e/_DCRxyKP https://amzn.to/3MgBFnn https://amzn.to/4dyLU1H https://www.banggood.com/custlink/KKGIEkkHBr PCI POST ANALYZER https://s.click.aliexpress.com/e/_DFl0qmB https://amzn.to/4dd8ihw https://amzn.to/3LTpeO7 TL460S PLUS PCI_E ANALYZER https://s.click.aliexpress.com/e/_DDTMw1N https://amzn.to/3WEsdi6 TOOLTOP ET120MC2 SCOPE https://s.click.aliexpress.com/e/_DkCeBRd https://amzn.to/4dCaz5L https://amzn.to/4dxOYLt FNIRSI 1014D SCOPE https://s.click.aliexpress.com/e/_Dm6vNuJ https://amzn.to/3AdZqK1 https://www.banggood.com/custlink/3DvShk2tkE NPS3010W 30V 10A PSU https://s.click.aliexpress.com/e/_Dc9s4UL https://amzn.to/4dzl2yM T12 STATION WITH M8 9501 HANDLE https://s.click.aliexpress.com/e/_DesbPUr https://amzn.to/46E73W6 M8 9501 HANDLE https://s.click.aliexpress.com/e/_DkmbgGj YIHUA 982 Soldering Station C210/C245 https://s.click.aliexpress.com/e/_DF88Zrz FNIRSI HS-02 PORTABLE SOLDERING C210/C245 https://s.click.aliexpress.com/e/_DCfzAaJ https://amzn.to/3Yv7Ma5 QUICK 861DW https://s.click.aliexpress.com/e/_DdsilAF https://amzn.to/3WDF4B5 https://amzn.to/4ci7rdW PROS'KIT SS-331H https://s.click.aliexpress.com/e/_DDSYUhd INFIRAY P2 PRO IR CAMERA + MACRO LENS https://s.click.aliexpress.com/e/_Dndyrj9 https://www.banggood.com/custlink/K3viRzkFzl https://amzn.to/4coSRle https://amzn.to/4coSV4s TOOLTOP ET13S THERMAL CAMERA METER https://s.click.aliexpress.com/e/_DExNv7N ET13S MACRO LENS https://s.click.aliexpress.com/e/_DlwnDKL OPTICAL MICROSCOPE https://s.click.aliexpress.com/e/_DmPmKAB https://usa.banggood.com/custlink/GKKIEzU87t https://amzn.to/4dzBA9G TOMLOV TM4K AF FLEX https://amzn.to/3LY0YKs https://tomlov.com/products/tomlov-tm4k-af-4k-8-autofocus-flex-arm-hdmi-digital-microscope?utm_source=KOL&utm_medium=YTB&utm_campaign=YTB-LER-JNAFFLEX&utm_id=YTB-LER-JNAFFLEX&utm_term=JN-AFFLEX TL866 II+ PROGRAMMER https://s.click.aliexpress.com/e/_DDFPQyx https://amzn.to/3SGKL05 CH341 PROGRAMMER https://s.click.aliexpress.com/e/_DCkZJQx NC-559-ASM FLUX https://s.click.aliexpress.com/e/_DeGOWh9 DESOLDER BRAID (I use size 8045) https://s.click.aliexpress.com/e/_DnFodlD https://s.click.aliexpress.com/e/_Deo6T8f HX-T100 SOLDER (0.6MM) https://s.click.aliexpress.com/e/_DnORpAT ESD-11 TWEEZERS https://s.click.aliexpress.com/e/_DdlU1UX Learn Electronics Repair is now on Discord! Come and join the fun, it's free. https://discord.gg/vam6YC8vwU If you would like to support this channel You can send donations https://www.paypal.com/paypalme/youtubeLER You can subscribe to Patreon https://www.patreon.com/learnelectronicsrepair You can click Join to become a channel member Thank you Richard