My parents philips 42pf7320/37 plasma tv has a bad picture. my boyfriend and i recently acquired it in the hopes we could fix it. the screen has many lines going across and up and down it. the color also bleeds. light colors tend to bleed up and down the screen. lastly the hue is very red around these abnormalities. we have looked and the power board and what we believe is the video board for bad solder joints. we haven't found anything that looks "wrong" yet. i was hoping someone here might be able to speed up our hit and miss process and send us in the right direction of what we should be looking at. if anyone has pictures of what we are looking at with labels pointing towards the different boards and parts (or even pics with a REALLY good discription of where things are located and what they are) that would be extremely helpful and much appreciated. thanks
I am having the same problem with my TV. I believe that the Y-Buffer Driver IC's are bad. There are two small boards on the left hand side(looking at the TV from the back) with 6 small heat sinks on each of them. If you look closely at the boards, it ill say Y-BUFFER on them. There are ribbon cables that run from them to the Plasma screen.
In my TV, several sections of the screen do not have lines in them. These driver IC's are not hot, however the sections of the screen that have lines in, the drivers are hot to the touch. In order to verify that the chips are indeed bad, I am going to swap one that I think is bad with a good section and see if the problem moves. If this is the case, the boards can be swapped out, or chips replaced depending on what kind of parts I am able to find. The chip that they use is SN755867. I haven't been able to locate a source for the chips yet.
The problem turned out to be these SN755867 IC's on the Y-Buffer boards. I was unable to remove the IC's using a solder reflow station at 240C because of the RTV glue used to attach the heat sinks did not soften at this temperature. It may be possible to remove these IC's with a lot of work by lifting individual pins and prying the IC off. I am not sure if there is a heat sink slug in the center of the IC. Tesla411 as well as Sierra IC claim to stock the replacement IC's but didn't respond to my request for quote.
Using a refrigerant, I sprayed the heat sinks on the PCB which cooled the chips down to about -50degrees Fahrenheit. With the chips at this temperature, most of the missing lines on the screen returned briefly. I ended up replacing both the upper and lower Y-Buffer boards and this fixed the problem. Due to the high voltage( about 430V) through these IC's ;I don't know how long the replacements will last. I only had horizontal lines on the screen and not vertical as mentioned above.
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horizontal lines across screen
I have a similar problem, my Tv was purchased in 12/05, model 42pf7320a/37 ; while veiwing one afternoon, I looked away from the screen and when I looked back I notices verticle lines throughout the screen, it appears as though the white and red lines are distorted green appears to be ok. Is there a solution that is cheaper than buying a new TV?
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