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7K views 27 replies 5 participants last post by  mvalent000 
#1 ·
Going to attempt to replace buffer chip on sdr board, buying a weller wes51 station, is this a good one for this type of repair?
 
#2 ·
It can be adequate, depending on the method used. Short of buying a hot air station I would not spend more than this. I would recommend a wedge tip to hold more heat for removal, and you will need lots of eutectic solder or some chip quick.
 
#4 ·
Most of the better suppliers have hd it in the past. I have not bought any in over a year, however, and understand prices have risen. I suggest checking several sources such as Acme, Encompass, Andrews, MCM, DigiKEy, etc.
 
#7 ·
Well that didnt last long, I bought some chip quik and tried to unmount the old buffer chip and it appears to be soldered in the middle of the chip too, I would take it that you need hot air to unmount the old chip? I am just going to solder in the new caps on the power board and buy a new sdr-u board. This site is really awesome and provides alot of references!
 
#8 ·
Not soldered, but glued. If you use the technique that I have described here the chip gets hot enough to melt the glue. I never use chip quick. I use a lot of eutectic solder to form a large bead around the entire chip. This holds enough heat to keep all sides melted and the chip lifts rigth off. Hot air is nice if you can afford the investment, but even in the repair business, I never could.
 
#9 ·
Your post has been moved to a more appropriate location to make information easier to find and to make it more likely that others who are interested will find your post.
 
#12 ·
Well looks like I learned something the hard way, I installed the new caps in the powerboard, put the old sdr u borad in and turned it on to see what would happen, it came on but with some lines screwed up, so i unplugged the top sdr from the y sustain, and turned it back on and blew a chip in the lower buffer baord! Oh well gotta get 2 now..
 
#17 ·
This is good info. I'm also trying to repair an SDR-U board out of my P50S601. This board has 1 bad chip. My TV is up and running thanks to this forum. I installed a new SDR-U board but would like to have a spare just in case. I never worked with flatpacks before so I knew this might be a challenge.

After removing as much of the silicone as I could, I tried to run a bead of solder around the chip but the solder would just ball up on the end of the soldering iron. I'm guessing this was due to silicone residue on the pins. I'm not sure what to use to clean the pins better. So I went to plan B and cut all the pins from the case with an exacto knife and desoldered them from the board. This is where I also found out the the chip was bonded to the board. I then decided to hold off until I got more info.

So my question is, does the adhesive under the chip server any other purpose other than to hold the chip in place for assembly? Is it necessary to use special adhesive for heat dissipation?

I used to work with modules that were installed in an F15 radar system. These modules contained ECL gate arrays that ran very hot. These gate arrays had to be bonded to the board with a special silver epoxy for heat dissipation. Otherwise, they would burn up.

Thanks,
George
 
#18 ·
Hi George, well I did use some desoldering wick and flux and removed the solder form the pins, I know I had it all off and tried to pry the chip from the board and the old chip broke, so i chipped off the rest of it and all that was left was the small square middle piece bonded to the board, it was sort of a small copper square, so I had to put ALOT of heat on it to remove it. What appeared to be underneath bonding it to the board was a solder looking material, it was very silver in color so guess it could be the stuff you mentioned. I think hot air would work good with this but I am not a pro, but it sems to be what is needed to properly remove this. Of course you could just break the chip and remove the middle piece but then I dont know what is needed to install the new chip.....paste solder maybe?? This is getting way too touchy for me!! haha...well good luck on yours and let me know how it goes...
 
#19 ·
Very interesting. It sounds like yours was soldered to the board. I noticed the small square on the bottom of my new chips but couldn't really see it that well because they are sealed in anti-static bags. I was thinking about using my dremel tool to grind the chip down if I couldn't get enough heat on it. LOL Getting the chip off the board is the 1st order of business.

A friend of mine mentioned solder paste but that would require heating up the chip during installation. Then you run the risk of frying the new chip if you apply too much heat. I need to research this a little further. I've done a lot of soldering but nothing like this. Another option would be to bond a heat sink to the top of the chip. Another thing, I'm not going to seal the pins with silicone. It's not really necessary.

Anyway, I'm going to attack mine this weekend. I'll let you know how it turns out. This is just a spare board for me so I'm not that concerned but it would be nice to get it right. I won't even be able to test this board unless my TV dies again. It took quite awhile to align the SDR connectors. I don't want to do it again unless I have to.
 
#20 ·
I finally got the the bad chip off of my SDR-U board. What a chore. As it turns out, there was plate on the bottom of this chip that was soldered to the board for heat dissipation. So I put the largest wedge tip that I had onto my soldering iron and tried to heat up the chip. No matter what I did, I couldn't get enough heat through the chip to break the solder bond underneath. I even tried heating up the back side of the board with no luck.

So finally, I put some flux onto the chip and heated up the chip by feeding lots of solder to tip of my iron so the heat would spread out. This only allowed me to break up the chip by putting some pressure onto the side of the chip with an exacto knife. Finally, a small piece to the plate underneath the chip was exposed. As soon as I touched it with the soldering iron, it popped off.

I lost a couple of pads in the process. Fortunately, the lost pads were tied to the pin next to it so the board is still useable. I was able to find a new SDR-U board on Ebay for $75 (as least that is how it was advertised). The seller (in New Jersey) is still on Ebay with more boards that he sells paired up with the SRD-D board for $139. Search for J6079 or J6080. The new board is working great in my TV.

Repairing this board didn't come out as good as I hoped but if I paid someone else to do it, it would have cost me at least $75 anyway.
 
#21 ·
Lifted pads are not uncommon, particularly in DIY work where you don't have the right equipment to control temps. You can still use the board in many cases if you carefully scrape the trace remaining to the copper, tin it, then take a strand of wire, smaller than the width of the trace and lay it along the tinned area and solder it down, leaving enough to reach the pin. Cut the remaining length to just long enough to lay over the part of the pin that solders to the land, then touch your iron to the pin to heat it enough to solder the wire. Flux helps, and if the wire is aligned carefully, the solder and gravity will keep the wire in place while the solder melts enough to make the connection.
 
#23 ·
lcaillo, Thanks for your reply. Yes, I've done that before but never on something this small. Luckily, the pads that lifted are tied to the pins next to them so I'll just bridge over to the next pin. I was really kind of surprised to see the pads missing. Once I cut the legs off of the chip, I really didn't put a lot of heat down to remove the pins from the pads. Next time I'll be a little more careful.

You seem to have the technique down for removing these buffer chips. What soldering iron are you using? I have a Weller TC202, 60W iron, fixed temp. with various size tips. I used my largest tip which is wedge shaped approx. 1/4" in diameter. I couldn't for the life of me get enough heat through the chip to unsolder the plate on the backside of the chip. I almost pulled out my monster 100W iron with a 1/2" tip but I restrained myself.

I think next time I'll drill a hole through the center of the chip until I reach the plate. I'll them put the soldering iron directly to the plate.
 
#26 ·
Actually, I have never changed buffers on these models. I have on others and they were not soldered in the middle. When I run into a chip that I think is soldered in I either use hot air or place a ball of solder on top of the chip after cutting the pins off. I have heard of using thin strips of copper slid under the chip to get the heat to the plate, but never have tried that method.
 
#24 ·
Hey George, thats sort of the same thing I had to do to get it off, just broke the chip...I would guess it would take hot air or some kind of preheater to properly remove these chips. Jason1976 posted some good info about repairing these boards, I thinks after the holidays I might get some time to sit down and try these repairs, the kids are taking up my time right now, haha, I have to get some wire or copper stenils, I watched a video on you tube on a guy soldering down some new copper traces. Looks like maybe with the time and a good magnifier AND a whole lot of patience this can be done sucessfully. I love doing this stuff, wish I would have went into the electrical engineering field like my brother, just a hobby for me though, but very interesting. Its funny the things you can actually repair with the right info like from this site!
 
#27 ·
I sort of figured this was something different because of the middle being soldered down, usually everything shows just the pins being soldered. Well anyways I got my new sdr boards, upper and lower, one I found on ebay for 40 and the other for 68 on ebay. The $40 one was out of a used set and not repaired, I think I lucked out on the price. The $68 one had a repaired buffer chip, the clear silicone used on it was a little sloppy but the board works fine. I did have a of a time getting the lines out until I tried to push one ribbon in a little harder and felt it bottom out, I turned it on and that section worked fine, so I just pushed in the remaining ribbons a little harder and they all seated and the picture is perfect!.. So A little $$ and two sdr boards and 2 caps later and its up and running, thank you all for the help and info, this site is priceless!
 
#28 ·
I have replaced a few of these IC chips. First time was using a hot air, heat station. This was done at a friends place of business which happened to be very circuit board related.

The easiest home remedy way to do this is to use a heat gun with a reducer tip that concentrates the air flow. Set the fan speed at the lowest output and the heat at 1/2 to 3/4 the max temp. After scraping off the sylicone with a hard piece of plastic (or your finger nail), clean up between the fingers with a needle and then clean the rest off as best as possible with a toothbrush and rubbing alcohol.

Place your heat gun directly over the IC, but not placing it directly on top and use the needle (or something similar but longer so you don't burn your finger tips) to gently pry up a corner of the IC. MAKE SURE the solder is all hot and melted or you could pull up the fingers under the IC that are part of the board itself!! (I've done this practicing).

There is solder behind the chip, it's not glue or a binding agent, it's solder. That is why it takes a while to be able to lift the IC off, the solder under has to melt.

When placing a new IC on the board, just place flux on the back of the IC chip and on the fingers of the chip. Put it into position using some sort of magnifying device....I use a jewelers loop. Line it up and put heat to it. Once there is enough heat the IC will float and you can make your corrections to line it up from there. Once you have it perfectly in position, put a little pressure on it with your needle or whatever you use to squish it down. Take the heat away and let it set for a second or two. Look through your loop to see if any of the fingers are above the solder if this happens take your soldering iron (hot) and place it on the finger to solder it down.

Hopefully this helps
 
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