I'm stuck with a power supply that has me completely stumped. I have three of these things, all three have the same problem. The PSUs power a range of TVs. These TVs often get stuck in standby, where turning it on will make the power LED dim. During this condition, the rails of the power supply are running, but at low voltages, around 1-2V, when they should be 24V/12V/5V etc.
The service manual is here: http://www.eserviceinfo.com/download.php?fileid=56543 (page 83-85 has the PSU.)
I ordered a broken PSU accidentally. Thankfully, it only had a busted PFC section so I disabled that, turning it into a simple bridge rectifier and filter cap. Now I can get the PSU to make a slight buzzing sound and output the 1-2V but nothing else. Another PSU I messed up (removed a resistor accidentally - replaced it with a solder bridge) seems to give similar issues.
The STBY_ON_OFF pin controls the switching of the PSU. Turning the TV on causes this line to go low. Normally it floats high. All the time during the time the PSU is attempting to start this is low. I am therefore considering the main board to be okay.
I have a scope here to do some probing, but I can't probe the primary side due to the high voltages there. I also have an accurate multimeter.
I am completely lost and would appreciate some guidance on how to continue.
The service manual is here: http://www.eserviceinfo.com/download.php?fileid=56543 (page 83-85 has the PSU.)
I ordered a broken PSU accidentally. Thankfully, it only had a busted PFC section so I disabled that, turning it into a simple bridge rectifier and filter cap. Now I can get the PSU to make a slight buzzing sound and output the 1-2V but nothing else. Another PSU I messed up (removed a resistor accidentally - replaced it with a solder bridge) seems to give similar issues.
The STBY_ON_OFF pin controls the switching of the PSU. Turning the TV on causes this line to go low. Normally it floats high. All the time during the time the PSU is attempting to start this is low. I am therefore considering the main board to be okay.
I have a scope here to do some probing, but I can't probe the primary side due to the high voltages there. I also have an accurate multimeter.
I am completely lost and would appreciate some guidance on how to continue.
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