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Help Needed - Thomson 27LCDB03B not working
micheldeman:
Boardnumbers may differ in versions. They are currently built in, so can't check the numbers.
I didn't receive the U6301's yet, so meanwhile I have exchanged some boards from the good working TV into the faulty TV and vice versa.
It looks like the powerboard of my faulty TV is fine as my good working TV has no problems with it. When I put the power board of my good TV into my faulty TV, I still have the same problem.
So I started to exchange the connector board. still same problem with my faulty TV
I exchanged the main board from the good working Tv into the fault TV, still same problem.
However, I had some situation where the faulty TV worked for some minutes or so and then shuts off. Power led still giving green. Remote controll not working except for the switch off button, greed led turns green. I can restart the TV afterwards by pushing the power button again.
What actually happends is the following.
The faulty TV turns on normally, picture and sound come on.
Then after some time (between 30secs and 2 minutes) the screen disappears, like it blows up, some red colour is visible and after that you only see some grey light on the back ground. I don't know if this is the back light still functioning or not. Also the audio disappears at the same time.
What I am thinking is that the power supply is overloaded at some point where it shuts down or something. Or the main board detects some fault and shuts down. No idea to be honest.
I just replaced the audioboard to test. Same problem.
I think I will try to replace the invertor board. May it overloads the powerboard somehow so that it fails to supply the power.
micheldeman:
I heave been testing a bit more arround and start to think that the power supply is underdimensioned for this 30inch TV. When the TV is brand new, the powersupply will stand the consumption, but when it gets older maybe not. However, I must say, when I used the connection board and main board from the good functioning TV in my faulty one, it took a bit more time before the TV shutted off, but still it was not functioning properly.
What else to try? I will check the board numbers and components of the different PSU's. May be there is a difference between the 27 and 30 inch version.
PS: I swapped the PSU permanently, so my good functioning Tv is now playing on the PSU of my faulty TV just for endurance testing purposes without any problem.
Acrantophis:
The problem could be that the circuit diagram I attached does not match your board and so could misleading, it would also explain why you have a different capacitor value to that shown. Having looked at the block diagrams for the 27 and the 30 inch TV's I would say that there are certainly difference between the two sets, the 27 has the audio, DC+DC, and PFC circuits all on the one board, where as the 30 has a seperate audio board. The connectors/wiring looms will also be different.
Perhaps opening a different post may be the way forward as there may be someone who might know more then me.
micheldeman:
Short reply to what you write,
in both Tv's, the audio is separated from the PSU board, unless your's is integrated, then there are differences. I must say, there are some differences between the boards, but they look compatible. Nevertheless, I will see what else I can try, first I will check whether there really no differences between the power boards.
Thanks,
Michel
micheldeman:
Hi Acrantophis,
Today I received ( a bit late) 2 pieces of a the 3843B ic's.
However, I can't identify pin number 1. The IC doesn't have a spot or something similar. It only has, apart from the number indication, a white line at one of the top sides. Would that indicate the top of the IC. I think it must, otherwise there is no other indication how to find pin number 1?
I have found that my TV plays when the source (e.g. a DVD player) is put on pause, so accepting still images. As soon as I resume the DVD, the TV shuts off. It looks like when the TV has to handle moving pictures, it shuts off, but still images, or when the DVD starts it's screensaver, it keeps functioning. I also can play for instance a music CD. Also then the TV keeps playing, it's only when playing moving pictures from DVD or other sources.
Looks like the PSU is incapable to supplying enough power???
What do you think?
I am trying to repair my original PSU. However, however removing the U6301 was already a difficult thing, as one of the pads is lifted. I will try to place the new u6301 very carefully.
thanks,
Michel
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