Forum > LCD TV forum
Help Needed - Thomson 27LCDB03B not working
micheldeman:
--- Quote from: Acrantophis on December 01, 2011,13:47:52 --- :08: Hi five Astracat! Together we've cracked it, appreciate the help. :c017:
Changing U6301 has resolved the problem, TV now back up and running. Just to confirm for anyone looking to fix the same power supply showing the same symptoms and they should subsequently stumble upon this post. The dc voltage to pin 7 of U6301 should be around 14V dc when working correctly. If you have the skills to lift the pin 7 re-measure the voltage at the PCB sniff point and see if it goes up to 15V which supports the IC failure as I found.
--- End quote ---
Hi, with interest I have been reading this tread as I also have a faulty power supply board. It also has a faulty U6301, apart from some other components. Where could you get the replacement for U6301? I am living in Coventry and have difficulties getting hold of these components.
I have put the list of components that I need here:
Q6301 -> STW12NK80Z
U6301 -> UC3843A
R6310 1206J10 (smd) smd size 1206, 10 Ohm (1/8 watt min.)
R6311 20K (smd) (1/8 watt min.)
R6327 1K (smd) (1/8 watt min.)
D6304 4146 (smd) (1N4148 Fairchild)
R6312 -> 0,27 Ohm 2 Watt
R6301 -> 68K 2 Watt
Q6302 -> MPSR44 (MPSA44G ON Semiconductors)
D6303 -> 4148 (smd) (1N4148 Fairchild)
Optional:
CY6201 -> 2200P, 250V (YL)
CY6202 -> 2200P, 250V (YL)
If anyone could help me out getting these components together, I would be very grateful, or even if somebody could help me with soldering of these smd components, that would be fantastic.
some pictures of my PSU can be found here:
http://www.mijnalbum.nl/Album=WQDMNCI3
thanks,
Michael
Acrantophis:
Mike, are you looking to make the repairs or do you want someone to repai rthe board for you, your post is confusing as you ask where to source parts but then go on to ask if someone could help do the de-soldering and soldering. I can tell you where to get the SOIC8 device U6301 from and probably most of the other items, but I don't like seeing people waste money buying items that they don't need to so before we go any further can I ask how you have concluded so many items need to be replaced?
micheldeman:
Hi Acrantophis,
let me try to tell the story in short. I was living in Sri Lanka and brought the TV earlier from the Netherlands (Bought accross the border from a Germany's Media Markt for 1100Euro). It's a 30LCDB03B, which has the same PSU board as the 27LCDB03B.
At a certain moment, when switching on the satellite receiver, the TV (connected via scart) gave a bang and a flash and was broken. I found that the U6301 was burned, it's used for automatically switching on the TV when it gets an (external) power on signal. Together with a friend from the Netherlands, who is in electronics, he suggested to replace the parts and some surrounding ones to be sure. However, I couldn't get the parts in Sri Lanka so got a replacement PSU from one UK tv parts web site. I replaced the PSU with the new one and there was no need anymore to get the PSU board fixed. Meanwhile, we have moved to the UK and so the TV. After a short while, the TV broke down again, it starts, but shortly it sort of powers down. So in fact, I have 2 defect PSU boards. I think the power boards are a common problem for these thomson TV's. You also don't find the brand in the common UK electronics shops (anymore).
Recently, I could get a same TV (27LCDB03B) from gumtree for just one pound, which is now playing. Has only a slightly problem with the LCD screen, kind of memory/burned in problem.
Then I found your tread and was wondering whether I could get my old TV fixed again as it is a nice piano black 30inch one.
I am not an electronics myself, but have some basic knowledge. I am always kind of challenged to get my equipment fixed again and oftenly go on forums to get the problem solved. I Have done washing machines, the power supply of our microwave, rewinded the tweeters of my hifi speakers, repaired our dishwasher, fixed the ceramic cooker, DVD player, my stereo tuner, do my own car repairs, toys of our kids, have done the water and electrics in our house in Sri Lanka, etc, etc, etc. Just as a few examples to mention the type of person that I am in that regards.
So the TV is now under our bed, waiting to get alive again. I am reluctant to just throw it away without trying to fix it first myself. I could do the soldering, but the U6301 might be a a bit too challenging. However, I can give it a try. I also could send you both PSU's if you like, but for the second one, I haven't investigated the reason. It could be just the capacitors as mentioned often as reason for power failures.
thanks,
Michael.
Acrantophis:
Mike, here is how I would suggest removing the damaged I.C. but remember not to over heat the solder to much as you may end up damaging the tracks of the PCB.
You will need:-
UC3843A - Obtainable here:- http://uk.farnell.com/unitrode/uc3843ad8/pwm-controller-smd-3843-soic8/dp/1101425
or
http://uk.rs-online.com/web/p/current-mode-pwm-controller/6899954/
Soldering Iron with a fine tip
Solder
Possibly a solder sucker or some desoldering wick
A scalpel blade N#11 or other suitably sized blade that can be inserted under the device.
A fine tipped pair of tweazers to position & hold the new device in place whilst soldering.
What to do:-
Firstly - note the orientation of the device. Pin 1 is identified by either a notch at one end of the device or a spot. This should be at the top of the device and pin 1 will always be the top left pin.
Solder all of the legs of the device along one side so that they are all shorted together. Remove heat.
Take scalpel blade - re-apply heat to solder so that it becomes molten and then ease blade under device. Whilst solder is still molten ease device up away from board on this side. Repeat the above for the other side, once the device is lifted away from the board on either side you can then re-heat solder both sides of the device and hopefully remove the compenent from the board.
Clean up any excess solder from the pads with the aid of the de-solder wick or solder sucker, try not to lift the pads by excessive exposure to heat though.
Take the new device with the tweazers and position it so that the legs line up with the pads and the device is in the correct orientation as mentioned at the beginning regarding the removal of the faulty device. Solder the new one in place being sure not to short any of the pins together, (if you do use the de-soldering wick or solder sucker to remove excess if you can not remove it with the soldering iron itself).
Regarding the other board I would certainly suggest replacing the electrolytic capacitors they only cost pennies so its hardly going to break the bank. If you need me to see if I can identify part numbers for you from RS or Farnell just shout and I will see what I can do.
micheldeman:
hi Acrantophis,
thanks for your extensive explanation. I have been on the web site of farnell and placed most of the parts, except the smd resistors (was thinking to use conventional ones), in my shopping basket. In some cases I needed to order a minimum of 5 or 10 pieces of a component. That's fine but I am with about 12GBP still under the minimum order amount of 20GBP.
Therefore I was thinking first to try to replace the capacitors on my other board. That will cost indeed just a pound or so. If that would solve the problem with that board, I am there already. I can then still decide later on to try to repair the first board or not.
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