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samsung y buffer ic's

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Ianm:
Hi All
New On here but been in the trade for a long while now and I am workshop based (that's the intro over   :sign0144: )
I replace these Ic's  and use a PCB preheater and a hot air rework station with a Quad flat pack nozzle on it, works great,
to remove the silicon glue I first remove the thick of it with a sharp blade then go around the IC with a fiber pencil,
the IC's I get are from China  and re flowing the new ones onto the pcb are no prob , use good smd reworking flux

leo_the_noob:
I'm a newb myself and am going to attempt the replacement of the IC chips myself . I also have the LJ41-05121A and 5122A Samsung buffer boards. I need to decide how many chips need replacement first. I have a hot air station and some experience with BGA reflows so I think I'm up for the task. What is the proper procedure to test these buffers and identify good/bad IC chips? One board has a burned IC on it so that is obviously bad but I'd like a way to check them with a meter if possible. Thanks in advance for any help.

sidecutter_5:
hi,leo best policy is to replace all the chips on both upper and lower y buffers.if one has burned out it's only a matter of time before another one craps out.and taking your ysus board fet's out again.
these buffer boards are a crap design in my opinion,as there are no heatsinks on the chips and as it's usually the top buffer that fails i can only assume that it is a heat problem.
have done this repair myself having limeted knowlege of smd chips so you will not have a problem.
If you are keeping the tv for yourself fit two silent 50 mm pc fans over the buffers/ysus fixed to the chassis rails.
I used a seperate 12v psu and added another 240v 5v coil relay on the psu linked to the 5v start up relay
get a good laptop charger or simalar (fits nice inside the tv)

sidecutter_5:
checking the ic's
i will probably get reamed for telling you this
In the center of the buffer boards there is a matrix of holes about 3/4 inch square this is the ground,
make sure you have a good connection to this (flux in the holes etc)
test for shorts on each connector going to the screen cables
you can trace the tracks on the board to the bad chip.

leo_the_noob:
I had not received a reply for a while so stopped checking on my post. Thanks for the help sidecutter. Using your instructions it looks like only the top IC im my upper buffer is shorted. I only ordered 3 buffer IC chips about 3 weeks ago so I'm still waiting on them. So in your experience replacing the 1 bad IC will be a temporary fix? How many of these repairs have you done and what has been their life expectancy so far? Thanks again for your help!!

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