Optocouplers that use a bipolar transistor (by far the most common) are specified in terms of _current transfer ratio,_ that is the ratio of transistor collector current to input diode current. It is much better to think of them in these terms than in terms of "resistance" of the transistor. There are couplers that use a photo FET instead of a bipolar transistor. They _are_ reasonably thought of in terms of output resistance. I've never seen a FET coupler used in an SMPS feedback circuit. In typical SMPS feedback circuits the transistor operates at less than one millampere, maximum. Current transfer ratios depend on the specific device, but something around 100% is fairly common, so the IR emitter would also operate at something around 1 mA maximum.
No, please don't. Just check voltage on output to make sure the output side is completing the circuit when you have the 1.1 volts across the input, otherwise you can still use you meter in diode scale too, to check.
There is a electrical connection from hot to cold. It is called the chassis (frame ground.) It is where many problems can be propagated from the hot to cold side. All decoupling caps on the hot side go to chassis ground, all suppression caps on the hot side go to Chassis. When either fail the current can and does fold back from cold to hot or forward from hot to cold.
Hello Bro...hv got problem with my Samsung smart TV, power indicator light does not ON. I have changed 2 boards, the Main and Power Board but still noughts.. The TV has Power Board, Main Board, T Con Board and the camera board. What's the likely culprit?? Ur expert opinion is very much appreciated. Hassan from Malaysia.
I BigDog, i am from Portugal (Europe). At the moment i am crossing some dificulties. I can´t manage to pay rigth now the course that you offer for a great price. I took 18 hard months to pay my Oled TV, cause i really enjoy it, but 6 moths before 2 years garantie past... The TV doesn´t turn on, and no IR signal. I have noticed that , power supply is not given any output. Everthing ok until we get DC power at the capacitors before the bridge rectifier, than i saw a open fuse and many components that are short cuted and others open. I can´t manage to get the electrical scheme. I had study electronics at 30 years ago...i went to study Electromechanics before the first 3 years course of electronics. I can do maintenance at a 250.000$ CNC machine, but I know that i need a lot more knowledge to start repairing TVs, it´s a diferent area to me. This hard moment will pass, and will come to adress to your course later. Regards, Pedro
From my personal experience, people need to be careful with samsung tv power supply, because you still can get a nasty shock from the cold side too . I did receive a nasty shock from a 40 inches samsung led tv power supply on the cold side .
Cold does not mean it can’t shock you, ideally it should not kill you but even that may not be 100% true all the time. Remember to always understand what you are doing and if you don’t wait until you learn (like from the ART course)! Glad you are doing well!
I encourage everyone to subscribe to the repair course. Its not expensive and the lessons are easy to understand and i have enjoyed watching them.
Awesome. It helps me a lot troubleshoot my mini split heat pump installations. Thank you. HVAC Contractor.
Excellent explanation, very clear and professional. Congratulations.
Great video and excellent explanation, as always.
Fantastic explanation for us newbeeys, Just subed
Thanks as always big dog. APPRECIATE You !.
Always
Thanks for the video and the knowledge.
You bet
Another good video. Learned a lot
Optocouplers that use a bipolar transistor (by far the most common) are specified in terms of _current transfer ratio,_ that is the ratio of transistor collector current to input diode current. It is much better to think of them in these terms than in terms of "resistance" of the transistor. There are couplers that use a photo FET instead of a bipolar transistor. They _are_ reasonably thought of in terms of output resistance. I've never seen a FET coupler used in an SMPS feedback circuit.
In typical SMPS feedback circuits the transistor operates at less than one millampere, maximum. Current transfer ratios depend on the specific device, but something around 100% is fairly common, so the IR emitter would also operate at something around 1 mA maximum.
The best explanation! Thank you
Added to my playlist. Very informative. 🤔😏👏😇
Awesome! Thank you!
Diodemode on a dmm can check an opto quick
Yes, but I was really just showing how it works. Thanks for watching.
How can I contact you need some info to sign up for the coarse 😊
so to test octocoupler on tv power board can i just put a 20ohm rersistor betwen output to bypass it?
No, please don't. Just check voltage on output to make sure the output side is completing the circuit when you have the 1.1 volts across the input, otherwise you can still use you meter in diode scale too, to check.
@@bigdog8882 ohh ok great to know thank you
There is a electrical connection from hot to cold. It is called the chassis (frame ground.) It is where many problems can be propagated from the hot to cold side. All decoupling caps on the hot side go to chassis ground, all suppression caps on the hot side go to Chassis. When either fail the current can and does fold back from cold to hot or forward from hot to cold.
What is heard only circa 10sec interval clicking sound coming from one relay in the power board.
Hello Bro...hv got problem with my Samsung smart TV, power indicator light does not ON. I have changed 2 boards, the Main and Power Board but still noughts.. The TV has Power Board, Main Board, T Con Board and the camera board. What's the likely culprit?? Ur expert opinion is very much appreciated. Hassan from Malaysia.
Maybe backlight issue
I BigDog, i am from Portugal (Europe). At the moment i am crossing some dificulties.
I can´t manage to pay rigth now the course that you offer for a great price.
I took 18 hard months to pay my Oled TV, cause i really enjoy it, but 6 moths before 2 years garantie past... The TV doesn´t turn on, and no IR signal. I have noticed that , power supply is not given any output. Everthing ok until we get DC power at the capacitors before the bridge rectifier, than i saw a open fuse and many components that are short cuted and others open. I can´t manage to get the electrical scheme.
I had study electronics at 30 years ago...i went to study Electromechanics before the first 3 years course of electronics. I can do maintenance at a 250.000$ CNC machine, but I know that i need a lot more knowledge to start repairing TVs, it´s a diferent area to me.
This hard moment will pass, and will come to adress to your course later.
Regards,
Pedro
I have a onn roku tv and all it does is go to logo screen then off over and over
From my personal experience, people need to be careful with samsung tv power supply, because you still can get a nasty shock from the cold side too . I did receive a nasty shock from a 40 inches samsung led tv power supply on the cold side .
Most likely the LED circuit if it uses a 300+ voltage rated filter capacitor.
Cold does not mean it can’t shock you, ideally it should not kill you but even that may not be 100% true all the time. Remember to always understand what you are doing and if you don’t wait until you learn (like from the ART course)! Glad you are doing well!
@@hernancoronel; I did not start repairing power supplies recently, OK?
Hairy stuff & definitely advanced tech compared to the CRT B&W from yester year!
Black lines matter.