I'm looking for some advice on fixing a SMPS (LAD6019AB5) based around the 3842ADM chip. It's supposed to run a small 19" TV.
The fault is that essentially it doesn't work. Which isn't strictly true in it's entirity.
To elaborate..... With the TV connected to the SMPS PSU, the PSU is turned on/powered up, the TV doesn't work - (almost) no output, only around 3v at the output. On the other hand, disconnect the TV from the PSU, power up the PSU and I get the normal 12.25v. Usually when the TV is then hot-connected to the PSU (i.e. still powered on), the voltage disappears back to the 3v mark. Occasionally, however, the TV sparks up and works normally. Once we get to this situation of the TV/PSU working together, the TV can be powered off and on (in/out of standby) without problems - the PSU continues to work normally.
Turn off the PSU at the mains and when it's powered back on with the TV connected, nothing again.
When all is working, the TV takes 0.1A in standby and 3.85A when powered up/working. The PSU is rated at 5A output @ 12v. Incidentally, the TV is good (tested on another power unit).
The PSU has no apparent visible damage (burnouts, etc. anywhere), no aroma of anything previously getting hot.
These SMPS power supplies are a mystery to me (I get the basic principle, but not the detail of why they can go wrong - other than blown diodes/FETs, etc. for which I've checked - if anything such as these components were defective, I'm sure the PSU/TV combo would never work).
Is anyone able to give me a clue as to where to look / what possible components to change?
Thanks in advance - and in hope of a fix.
Dave
The fault is that essentially it doesn't work. Which isn't strictly true in it's entirity.
To elaborate..... With the TV connected to the SMPS PSU, the PSU is turned on/powered up, the TV doesn't work - (almost) no output, only around 3v at the output. On the other hand, disconnect the TV from the PSU, power up the PSU and I get the normal 12.25v. Usually when the TV is then hot-connected to the PSU (i.e. still powered on), the voltage disappears back to the 3v mark. Occasionally, however, the TV sparks up and works normally. Once we get to this situation of the TV/PSU working together, the TV can be powered off and on (in/out of standby) without problems - the PSU continues to work normally.
Turn off the PSU at the mains and when it's powered back on with the TV connected, nothing again.
When all is working, the TV takes 0.1A in standby and 3.85A when powered up/working. The PSU is rated at 5A output @ 12v. Incidentally, the TV is good (tested on another power unit).
The PSU has no apparent visible damage (burnouts, etc. anywhere), no aroma of anything previously getting hot.
These SMPS power supplies are a mystery to me (I get the basic principle, but not the detail of why they can go wrong - other than blown diodes/FETs, etc. for which I've checked - if anything such as these components were defective, I'm sure the PSU/TV combo would never work).
Is anyone able to give me a clue as to where to look / what possible components to change?
Thanks in advance - and in hope of a fix.
Dave