Mitsubishi WT-46809 picture bow

With the set unplugged of course, lightly take a clean paintbrush and with a small nozzle connected to to a vacuum, lightly dust the boards off, Your problem with the set is not related to the dust. You have bad STK convergence IC's, these are soldered into the printed circuit bard. if you have no printed circuit board repair experience, the best advice would be to call in a pro to assist you with this repair.

Mitsubishi Convergence IC Replacement
Model WS-55859, WS55869, WS55909, WS65909, WS73909
By Larry Dillon

I will first start out by saying, it is very important that you have some soldering experience working on solid state printed circuit boards and that you know that too much heat from the soldering iron will most likely ruin the pc (printed circuit) board. If this happens, it can be a very difficult repair. The boards are no longer available for these sets from Mitsubishi so I cannot stress enough, if you have no soldering experience, let a pro assist you in this repair. One more very important thing to remember and NOT DO!! If the convergence is way out or cannot be adjusted by the customer controls, do not go into the service menu and try to adjust the convergence. It will only make it very difficult for you to adjust the set after it has been repaired. The service menu adjustments are to make MINOR drifting alignments, as over time, the adjustments may drift a bit due to part tolerance changing. I am using the adobe reader eight (8). If the page numbers do not match up as I have explained, then you will need to upgrade to the newer version eight (8).

Next, letÂ’s get together the equipment you will need to work on this puppy. You will need a # 2 Phillips screwdriver to first remove the backboard in the rear of the TV set as described on page 10 of the service manual. Next, you will need a small soldering iron with a desoldering bulb to remove the solder on the pins of the ICÂ’s. I recommend an inexpensive one from Radio Shack. It is a 45 watt type, item number 64-2060. You can see it here http://www.radioshack.com/sm-buy-the-45-watt-desoldering-iron-on-http-ww.... Next, you will need a small amount of rosin core solder to re-solder back in the new convergence ICÂ’s. You can get that at Radio Shack also. The item number is 64-017, and you can see that here http://www.radioshack.com/product/index.jsp?productId=2062719&cp=&sr=1&o... Next, you will need whatÂ’s called heat sink compound or thermal paste. The item number is number is 55014135 and can be seen here http://www.radioshack.com/product/index.jsp?productId=2526910&cp=&sr=1&o.... You also might wish to pick up a small amount of solder braid to assist you in cleaning up the area around the un-soldered pins of the convergence IC after you remove it. It is very important to make sure you have no solder splashes or bits of solder lying around or across any of the adjacent circuits. Now we need to get ONE (1) STK393-110 convergence Amp ICÂ’s. I recommend getting those from here http://www.electronic-repair-kits.com/STK393-110.html. The reason I recommend this distributor, I have ordered many of ICÂ’s, a lot for a lot less money, but they are not original Sanyo ICÂ’s. Yes, these ICÂ’s in this Mitsubishi set is made by Sanyo. A lot of the less expensive ICÂ’s are not original and the aftermarket types made in China. I have heard also that some parts distributors buy factory reject ICÂ’s and sell them as good original ICÂ’s. That being said, it is up to you if you want to be back into your set several months down the road because of another convergence problem. Play it safe, and stay original. . You will also need a small multimeter or DMM ( digital multimeter) and know how to use it. You can get the five (5) amp pico fuses if you need them from http://www.bluestar-online.com/5_AMP_PICO_p/5%20amp%20pico%20fuse.htm.

Next, is a very important step. MAKE SURE THE TV SET IS UNPLUGGED FROM THE WALL SOCKET!! This may seem a bit redundant, but I cannot count how many times I have seen technicians rush into a job and forget to unplug a set from the wall. Now letÂ’s get into the set. First remove the back board by removing 20 or 21 screws from the backboard of this set. This is described on page 10 of the service manual. Next, remove the left and right speaker grill covers as well as the center part of the TV set in the front. These simply pull off so do not be afraid to pull on them a little, side to side till they come off. Now take off the front board by removing six (6) screws. This is all on page nine (9) of the service manual. Now, remove three (3) screws securing the entire chassis in the rear of the set as described on page 15 of the service manual. Next, unclip the two (2) chassis locks in the front of the TV set as the locks are shown on the front of the chassis on page 16 of the service manual. Now, slide the chassis out toward the rear of the unit and slide upwards to access the bottom of the printed circuit board.

Now, letÂ’s look at page 16 towards the bottom of the page. There right in the middle of the power board, the board in the middle part of the chassis, notice the large metal block with fins on it. On that block, which is called a heat sink, is a line that says IC8C01 & IC8C02 conv. Outputs. That is a mistake in this service manual. There is only one (1) Conv. output IC in this set and it is marked IC8C01. Now you want to first locate the two (2) pico fuses on the main power supply board. As if one or more of these are not bad, your convergence IC is most likely not the problem with the set. This is not always the case, as maybe the IC opened up and not shorted, therefore blowing out the fuses. I have not seen this condition too many times though. The fuse are marked ON THE BOARD, as F9A04 and F9A05. They are located next to or near a large transformer labeled on the board as T9A50.They do not look like regular glass fuse but more like resistors. Measure for a short or full continuity across both of them. If one or both are bad, DO NOT simply replace them, the IC is bad, and replacing them will cause further power supply damage. Fuses do not blow in this set unless there is a problem. . My experience has been, if a fuse or two are bad, find out why it blew. These are 5 amp pico fuses. And can be ordered from the link that I have posted above. These pico fuses control the plus and the minus 24 volts to the convergence IC. Also be sure to check the resistance of several feedback resistors. They are labeled on the PC board as R8C05, R8C06, R8C13, R8C14, R8C21, R8C22, R8C29, R8C30, R8C37, R8C38, R8C45, and R8C46. These resistors are flameproof and are 3.9 ohm resistors@ two (2) watts. The other resistors in this convergence circuit that sometimes will burn up are labeled on the board as, R8C07, R8C15, R8C23, R8C31, R8C39, and R8C47. These resistors are also the flameproof type. The values of these resistors are 150 ohms @ three (3) watts. Also, if you have the plus and minus 24 volts on the power supply but not on the convergence IC pins numbers 10, 12, 13, 15, 16, and 18, check the two coils labels on the board as L8C01 and L8C02. If one or more of these cols are bad, replace C8C05, and C8C03. They are 1000uf@50 volts.

Next thing you want to do is to carefully remove all of the solder on all of the pins on the convergence output IC. Make sure each pin is free to move around inside of the hole. Now, unscrew the two screws that attach the IC to the heat sink. Now remove the IC from the printed circuit board and the heat sink. Sometimes the silicone thermal paste dries up and you have to pry off the IC, but it will pop off. Next, do your best to scrap off any large amount or clumps of old thermal paste off of the heat sink. It does not have to be shiny clean though. Now, make sure all of the pins of the new IC are all lines up, and straight. It makes the re-install easier. Now, apply a liberal coating on the back side of the new IC, not too much as it will get all over the place. Just enough to coat the back side of the new IC. Now, insert the IC back into the board and making sure all of the IC pins go straight into the holes and do not bend, or short out against each other. Next, carefully solder each pin at a time on the board, watching and being careful not to short or bridge any solder on to the adjacent pins or circuit pads. Double, no triple check your soldering job. Clean up any excessive solder flux with a cue tip and alcohol. Reinstall the chassis and make sure that any plugs you disconnected are back into its proper connector and double check every plug and connector by hand, not by sight, for loose or shifted connections. Now, plug in the set and see if you did your job correctly. If the set will not come on, check the pico fuses again. If one or more are bad again, the IC is bad, or there is a short across one of the pins. If the set comes on, but the convergence is way out, you may have a bad feedback resistor or two. If you messed with the convergence before you replaced the IC, you may need a pro to assist you in making the final convergence adjustments. Good luck and be carefull!

Great instructions. Larry, is this procedure pretty much similar for the WT46807?