Blown IC Caused Dim Display In LCD Mag 700p
An LCD screen was brought to my shop by a young man. While the man waited, I powered up the LCD screen and the standby LED came on but the display was too dim to see. From Experience, either the fuse on the inverter board is blown therefore no power to the back lights or the actual board has problems. Let us find out.
A lot of useful information you can get from the back sticker on the back of the LCD screen.
Only three screws have to come off in order to go to the inside of the screen. Once these screws were off, the inside was revealed.
My main focus was the main fuse but as I was heading that way, I looked around and I saw something that was not normal. Can you see the blown part in the photo?
Well, if you have not spotted the blown IC from the previous photo, here, it is clear and marked with a red arrow. To my surprise, the fuse was not blown. That part number is 4511GM. It was not easy to get the part number but I was lucky to have the same exact board in my junk pile. Below is the link to the datasheet:
I pre heated the board and then went directly to take the old IC off to be replaced. I was not expecting this to happen but it did. Check out the next photo.
I guess I used extra heat with my re work station or the bottom area of that IC was already damaged. Either way, it has to be fixed.
I put the IC back to the board and I connected a wire to it. I usually use a transformer wire that is already isolated and I scratch both end of that wire to make conductive.
My apologies to you all out there for not posting this photo because I totally forgot to take picture of the finishing product.
Once I put everything back together and powered up the LCD screen; it worked for almost two hours before I called the customer to come and pick it up.
Mission accomplished.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.
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Note: You may check out previous post about fixing active speaker in the below link:
https://jestineyong.com/how-to-repair-charging-problem-in-iphone-5s/
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Robert Calk
September 6, 2017 at 10:19 pm
Good job, Waleed. The IC probably had adhesive underneath it. Almost every SMD IC I need to remove has adhesive sticking it to the PCB.
Waleed Rishmawi
September 8, 2017 at 3:48 pm
Robert: yeah, most of the time and sometimes I see solder beneath it and that is why I applied heat..I guess I applied too much of it.
Robert Calk
September 9, 2017 at 1:25 am
Yeah, I need to build myself a heat table to heat the backside of the PCB to make removing the bottom center-grounded IC's easier. But I don't think it will help for IC's that use adhesive. We need to figure out what chemical that we can safely use to help weaken the adhesive.
Waleed Rishmawi
September 13, 2017 at 1:46 pm
Robert: I use flux past to weaken the soldering joints and it helps to take off the IC without burning what beneath it of course with some heat..
Maurice Ball
September 6, 2017 at 11:11 pm
That was a interesting piece of fault finding.
Parasuraman S
September 6, 2017 at 11:19 pm
Great show indeed! Very masterly service!
David
September 6, 2017 at 11:47 pm
That massage was well framed for a good understanding,I will always follow your information to the later.
moshe jacobson
September 7, 2017 at 6:00 pm
Very nice Waleed!
daniel suo
September 7, 2017 at 10:11 pm
great work, keep it up. I guess that ic was taken out of the t-con board?
Waleed Rishmawi
September 8, 2017 at 3:46 pm
Daniel: not, actually it was taken out of a similar board and the same exact part number.
Yogesh Panchal
September 7, 2017 at 10:33 pm
Good job Waleed!
bela kokas
September 11, 2017 at 5:33 pm
very nice work.