I am having projection problems with my Mitsubishi VS-45501. This is my first time to work on a TV...so any help is much appreciated. I was told by a technician that all 3 tubes would have to be replaced??? It looks like an adjustment issue...but for what I know this could be bad tubes. Also, where could I find schematics for this TV...assuming I will need them to fix this problem. Here is a picture of what the TV is doing.
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First of all, your tubes are in excellent shape judging by your picture. The problem is in the convergence circuitry. A common problem with this set is broken solder connections to the convergence amplifiers. These are mounted on the huge heat sinks near the chassis edge. DO NOT REPLACE TUBES!!!!
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Fred, I sincerely appreciate your reply...it is very helpful! I am having trouble locating the convergence module. I find the large heat sink which is on the right hand side of the picture. But there is nothing attached to it. In fact the chipboard that this heat sink is attached to is standing on its edge. Also the majority of the circuitry of this board is covered by a panel, which I looked under but could find anything. I don't guess I really know what the convergence module/amplifier is. What is its shape? How many are there, are they labeled with STK...? Hopefully by looking at the picture you can direct me futher. Thanks a million.
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The large heat sink on the right has the convergence amplifiers (STK---s) attached to it. Check the circuit board connections for the STKs for bad solder connections. DO NOT use to hot of a soldering iron, you may lift the copper foil and only use rosin core solder.
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can you see the STKs in the picture...I dont know what one looks like? How many are there? Best I can tell the only thing that is attached to the heat sink is the chip board itself. On the chip board there is mulitple resistors, etc...but I can't find anything with STK on it.
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The STK IC's are mounted on the heat sink (u only can see the heat sink in the photo u provided) on the board that is mounted vertically on the right hand side.
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Thanks to sam2006 and fred I found the STK...for any other inexperienced person wondering what an STK looks like (in layman terms), they look like black boxes stuck to the side/bottom of the heat sink. In this case the STKs are located on the underside of the heat sink. That is why they aren't visble in the picture. They are 64mm wide x 8.5mm deep and black in color.
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Good job in finding the STK parts and the description you gave. What is the part number on your STK's? Have you found any pricing...was wondering how much they cost.
Best to you on your repair. Please give a follow up afterwards.
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They are 5.99 here and the shipping was <$7 for all 3 (one STK391-020 (IC) per CRT (cathode ray tube). The site doesn't list a name brand...but I hope the quality is good. Since other folks have told me that it could possibly be something else I didn't want to spend a whole lot on these ICs. Ebay has them listed at $6.99 + $5.99 shipping.
Now that I have spend a few nights learning about TV repair...I am fixing to have to learn to desolder and solder. Any tips... I was told to use rosin core solder? How exactly do you use a desolder wick? Do you heat the actual solder with the gun or do heat the wire running into the solder. Also when you are soldering the new ones in does the heat from the gun need to be applied to wire of the IC or the chip? Does the chip need any heat? I have soldered before but nothing this intricate.
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I found chemwik brand to be the best desoldering braid for these applications in removing solder from stk pins. 10-50L (50ft) or smaller 10-25L 25ft(BLUE) . First spread braid "widen braid surface area", put braid on the pin where solder to be removed, apply solder iron tip on the braid and apply some pressure to remove solder with solder iron tip. do that for each of the 15 pins on the STK391-020. Clean old heat silicone compound (white color) using a blade from the heat sink and apply a new silicone heat compound on the new STKS (spread silicone compound on the back of the stk). Tighten the screws and then solder the pins. Use solder guage 0.031" and use a solder tip between 1.6mm to 2.4mm with a 35W solder iron. Weller makes one of the best soldering irons WP35 (blue handle).
u might run in the problem that STKS are "glued" to the heat sink. Silicone heat compound dried and got hard. Use adjustable slip jaw pliers to remove stks.
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One of your previous posts spoke of using a soldering "gun". Guns are generally 100 watts and higher. Do not use a gun as they get too hot and you can easily damage the circuit board by overheating the thin copper circuit trace and it WILL lift off of the board...you will have a much bigger problem then.
As SAM2006 said, use a low wattage iron & keep the tip clean.
When soldering in the new STK avoid overheating any pin. If you dwell too long on a pin, the heat will travel up the pin and into the inside of the STK where it can damage the delicate internal circuitry. If in doubt, do just 1 pin and take a break to allow cooling, then do another pin and allow cooling again, and so on.
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Soldering is an art. As such, it requires much practice to gain sufficient skill/ability. Therefore, as a newbie it is most difficult to instruct you. Seasoned techs "know" by just looking that a connection is good or bad. In most cases, beginners apply WAY TOO MUCH solder (and too much heat) to the connection and it puddles up into a big ball...and can bridge across to other pins.
I've had to rework many fixes by other techs who just couldn't solder correctly.
Less is better. Before you begin, look around at other connections and study what they look like. They will be very shiny and sharp, not dull or a blob.
I apply the iron to the pin & trace at the same time for about 1 second, then apply the solder and get it to flow. Once it flows, I remove the solder and at the same time, I move the iron up and away from the trace vertically. This action causes the solder to form a nice clean joint with a small amount of flow up the end of the pin. (Note this assumes you are soldering an STK that has pins that protrude out the bottom of the printed circuit board).
If you happen to apply too much solder and get a bridge between 2 or more pins, use some desoldering-wick to absorb it all up from the pins that are bridged and try again in a few minutes after it cools some. DO NOT TRY TO REHEAT THE "BLOB"! REMOVE IT.
Again...less is better. You are merely trying to make an electrical bond, not a mechanical one.
Lenny
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I fixed the TV. Thanks to everyone that helped me! It works great. Soldering is really a piece of cake. The only advice I have to newbys is to know that it doesn't take long for the thin metal on the chipboard to become hot enough to flow solder. The STKs fixed it will no problem. While I was in there I cleaned the lenses and the mirror. Pretty good for a free TV. Thanks again to all the folks that helped me!
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