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Zenith IQC50H94Wi No Video Repair Instructions 2040 | Print |
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Tuesday, 04 November 2008 22:34


Zenith  IQC50H94W

No Video Repair Kit


Introduction

This guide will help you repair your TV if it has any of the following symptoms.

  • TV does not have video

Models known to work with this fix : Zenith IQC50H94W

The most common cause for the above problem is a faulty resistor. This repair kit will walk you through the steps to remove and replace the failed part. Note that we cover two methods below to remove the part. The first method is prefered.

Please read this guide completely at least once before you attempt to fix your TV. You may also want to print the document out. To do so click the "print" icon at the top of this article.



IMPORTANT: TV sets can hold a charge for a long time and can shock you even while unplugged if you are not careful.  It is advised that leave your TV set unplugged for at least 3 days before attempting the fix. This will give the set some time to discharge some of the stored electricity.



Running your TV set when it has a convergence problem will cause other components to get damaged.



Icons used in this document

This icon is used to indicate tips or tricks that will make the repair go smoothly

This icon is used to point out important items such as safety precautions

This icon is used to highlight additional notes.





Disclaimer

The procedures described in this document require access to potentially dangerous voltages, proximity to the CRT and its implosion risk, and other possible dangers lurking inside a television set. We will not be responsible for personal injury resulting from attempting these repairs nor damage to the equipment that may result from lack of soldering experience or inadequate de-soldering or soldering equipment.

While your TV symptoms may fit those described in this document, there is no guarantee that this kit will fix your problem. The actual cause could be elsewhere.





Shopping List

( Click Here to print just the shopping list )

Below is a short list of tools that you need to for the repair.

Item #1) TV KIT ( If you have not done so already order the correct TV repair kit from www.TvRepairKits.com)

Item #2) 35 Watt or less "Pencil" Soldering Iron ( See photo below )   Cost - 10.00 at your local Radio Shack store.






Item #3) Desoldering Iron - See Photo Below - Cost - 12.00  at your local Radio Shack Store



Item #4) Silver-Bearing Solder  - Cost between 3.00  - 5.00 at your local Radio Shack Store - Get the smallest diameter solder you can find.



Item #5) Solder Board - Costs around $1.99 at Radio Shack.   We highly recommend picking up one of these boards so that you can practice your soldering / de-soldering before doing the actual repair.





Item #6) Dip Socket  - Costs around 99 cents at Radio Shack.  These are inexpensive and great for praticing your sodlering. Simply pop it into the solder board shown above and solder / desolder a few times.



Item #7) Philips Srew Driver










Learning to Solder



Proper Tools

Having the proper tools makes all the difference in the world. With the correct tools soldering/de-soldering will be simple. With the wrong tools soldering/de-soldering properly would be very difficult. Also, contrary to belief,  you don't need any expensive or fancy tools to solder properly.  All of the tools you will need to master soldering can be purchased at your local Radio Shack store for under thirty dollars total.

So here is your Radio Shack shopping list again!

Item #1) 25-40 Watt  "Pencil" Soldering Iron ( See photo below )   Cost - $10.00 at your local Radio Shack store. This is absolutly the most important factor in learning to solder correctly. Do not fall for the fancy irons being sold such as the cold solder irons, butane irons, etc. All you need is a very simple 25-40 Watt pencil iron.  








Item #2) Desoldering Iron - See Photo Below - Cost - $12.00  at your local Radio Shack Store. This is the second most important tool you will want to own. This will make de-soldering the a breeze.



Item #3) Silver-Bearing Solder  - Cost between 3.00  - 5.00 at your local Radio Shack Store - Get the smallest diameter solder you can find.  If you can't find silver solder just get the thinnest solder you can purchase.



Item #4) Solder Board - Costs around $1.99 at Radio Shack.   We highly recommend picking up one of these boards so that you can practice your soldering / de-soldering before doing any actual repairs. Just make sure you buy the one that has the copper foil around the holes as shown below. If you buy the one without the foil around the hole the solder will not stick.





Item #6) Dip Socket  - Costs around 99 cents at Radio Shack.  These are inexpensive and great for practicing your soldering. Simply pop it into the solder board shown above and solder / de-solder a few times. You can also pick up a few resistors and cheap IC chips if you like.



Preparation and Practice

After the tools the second most important thing to master soldering is preparing the tools and  proper technique.


First lets start with preparing the iron for soldering.


  1. Plug in the soldering iron and let it reach a high temperature. This will typically take 5 minutes.

  2. Next wipe away any existing solder or contaminants on the tip of the iron with a wet sponge.

  3. Place the solder on the very end of the cleaned soldering iron tip. Keep the solder in place until it begins to melt. Move the solder all over the tip in an even coat. This is called tinning.


Now that the soldering iron tip has been tinned you are ready to pratice your soldering skills.


  1. Place the tip of the iron on the board at the base of the part that you want to solder. See the photo below.

  2. Count to 3 - As you count to 3 touch the end of the solder on the opposite side of the part your are trying to solder. It should melt quickly and make a nice volcano looking shape. See the photos below.

  3. If the solder globs up and does not form a volcano shape you are either using too much solder or your iron is  not hot enough yet.

  4. If you don't get it right the 1st time just repeat the above step until you get it right.



Correct



Incorrect

















Correct Solder shape shown below -Volcano shaped



Wrong solder shape shown below  - Too much solder or glob shaped.































Desoldering

Now that you have mastered soldering its time to practice your de-soldering skills.

First lets start with preparing the de-soldering iron.


  1. Plug in the de-soldering iron and let it reach a high temperature. This will typically take 5 minutes also.

  2. Next depress the bulb a few times to make sure its working and to blow out any old solder that may be still in the iron.

Now that the de-soldering iron is prepared you are ready to practice your de-soldering skills.


  1. Press and hold the suction bulb in while you place the tip of the de-soldering iron on the the part that you want to unsolder.  See the photo below.

  2. Once the solder begins to melt simply release the bulb. This will force the melted solder to get sucked up into the bulb and away from the board.

  3. Next you will want to blow out the solder by squeezing the bulb a few times over some tin foil. The foil will catch the melted solders its blown out of the iron.

  4. Repeat the same steps above for the remaining parts you want to de-solder.

  5. If you desolder a part and it still will not come loose there is probably a trace amount of solder holding it down. Just place the de-soldering iron on the pin again and jiggle it a bit. This will typically loosen up any stuck pins.






Here are two examples of both good and bad soldering.




Good Soldering Example



1) Notice that all the pins are separated and not touching each other.  In this photo you can actually see the space between each pin.



2) Smooth soldering – The soldering on each pin is smooth and shaped like a volcano.



3) All pins are soldered – None of them have been missed.







Poor Soldering Example…

  • See Photo Below) Pins are soldered to nearby pins. This is called a shorted connection or a bridged connection. If you create a bridged connection the TV will shut down when you try to power it on.  The power light may remain lit but the tubes will not light up. You may also hear a chirping sound. Note: If you power the TV on with a bridged connection you risk damaging the convergence chips or other components on the board.  If for any reason your TV will not light up after doing a convergence repair this should be the first thing to look for. If you find a bridged connection repair it ASAP. Most of the time the TV will just shut down and no further damage will occur.
  • Missing solder on some of the pins in the photo below.




  • The soldering was not smooth and looks clumpy. This is typically due to the soldering iron not being hot enough or using the wrong solder.  Always use the thinnest solder you can find and make sure your iron has been plugged in for at least 10 minutes before using. Radio Shack 80/20 rosin core solder is a good choice. Another good choice is silver solder.







Solution:

Always triple check you’re soldering before powering on the TV. Make sure none of the pins you soldered are bridged. You should be able to see a space between each pin if not desolder and resolder the pins again.









Unplug Power and all Cables



TV sets can hold a charge for a long time and can shock you even while unplugged if you are not careful.  It is strongly advised that you unplug your TV set from the wall at least 3 days before attempting the fix. This will give the set some time to discharge some of the stored electricity.  Do not plug your TV back in until the repairs are completed.







Remove all Cable TV, Speaker, Audio/Video Cables from rear of set.







Remove Rear Access Panel



Using the proper tools remove all the rear cover screws along the top, sides, and bottom of the rear panel.









Locate the Main Board an RP41 - Note that it is located on the large board near the edge. See the arrows below.




Note that your original RP41 may not look like the resistort below. This photo was shot after it was replaced with a new one.
The key is to just make sure you locate the resistor at location RP41 which is printed on the board.








Note: There are two methods you can use to replace the part.

The first method is the prefered method.  Using this method you will loosen and remove as many wires as needed so that you can flip the tray on its side. Once on its side you will cut one of the plastic rails to gain access to the part.

The second method would be to remove all cables, screws, etc from the board so that you can remove the board from the TV set. This method is covered at the end of the guide.

Method #1

Loosen all wire ties and remove any cables that are in the way. Mark all cables before removing.

Note: We do not reccommend removing the red flyback cables shown below.









Remove all the screws around the frame.







Tilt the board up so that you can get to the underside of the board...note that the photo below is an example photo and may not be from your exact model.






Locate RP41 on the underside of the board as shown in the photo below...Note that it is hiden under the black plastic rail which is cut away in the photo. (next step)





Using a pair of garden shears cut through the plastic rail. Caution must be taken not to hit or scrape the board while doing this step.




Cut both the left side and right side to remove the rail






Desolder and RP41

Note: We highly recommend using a desoldering iron like the one shown below. You can purchase one from Radio Shack for under fifteen dollars.





Using the desoldering iron slowly remove the solder from the pins on the convergence chips and any burnt convergence resistors as follows.

  1. Plug the desoldering pump in...Let it warm up.
  2. Position the circuit board so that you can get to the items that need to be desoldered.
  3. Press the pump bulb - and hold it in.
  4. Place it on the 1st pin to be desoldered - when the solder melts release the pump bulb.
  5. The solder will get sucked into the desolderng iron.
  6. Place the pump over a piece of paper and press the pump bulb to blow out the solder onto the paper.
  7. Repeat the steps above.


Example photo shown below of how the desoldering tool works...





Example using soldering wick instead!














Replace RP41.  Put the new one  into the circuit board. Note that on resistors direction/orientation of the resistor does not matter.





Once sodlered into place make suer you cut off any excess wire that is sticking out under the board so that it does not short out.
The original resistor wires are much longer than needed.




Reassemble The TV

Reinstall the TV in the reverse order that you disassembled it. Make sure that any plugs you disconnected are back into their proper connector. Make sure you double check every plug and connector by hand, not by sight, for loose or shifted connections.

Plug in the set and power the TV on. As mentioned above watch for sparks, glowing resistors, smoke, etc. If you see any of these conditions unplug the TV immediately and check your soldering, connectors, etc.



Leave the rear cover off the TV so that you can monitor it while it powers on. If you see any sparks, glowing resistors, smoke, etc unplug the TV immediately.







Repair Complete - Hopefully your TV is now fixed. If not review the troubleshooting steps at the end of this document.



 Alternate method for repair. This method involves removing the board from the TV.


Remove Cables, Screws, Clips from the Board


Next you will need to remove all the cables, cliips, and screws attached to the main board so that it can be removed from the set except for the large red FLYBACK wires. More details below....



Mark the cables with a permanent marker as you remove them. This will make it easier to put them back later.





Remove only those cables that are in the way.





Locate and remove all the screws on that are attached to the board. Note that there are several screws located in the center of the board also.







Pop the "wire bridge" clips up as shown in the photo below.








Remove the front plate from the TV......





Do not remove the RED flyback wires........




Do not reccommend removing the red flyback cables shown below. These are the only wires that will remain connected.

Pop the clips on the board to remove it from the TV...note that it if does not slide out easly there is likey a screw or wire that you missed.

Stop - Do not force it if that is the case.....




Once the board comes loose flip it around with the flyback wires still connected. Find and replace RP41.



After you solder it into position make sure you cut off any excess wire. Note that the resistor direction/orientation does not matter.







Reassemble The TV

Reinstall the TV in the reverse order that you disassembled it. Make sure that any plugs you disconnected are back into their proper connector. Make sure you double check every plug and connector by hand, not by sight, for loose or shifted connections.

Plug in the set and power the TV on. As mentioned above watch for sparks, glowing resistors, smoke, etc. If you see any of these conditions unplug the TV immediately and check your soldering, connectors, etc.



Leave the rear cover off the TV so that you can monitor it while it powers on. If you see any sparks, glowing resistors, smoke, etc unplug the TV immediately.







Repair Complete - Hopefully your TV is now fixed. If not review the troubleshooting steps at the end of this document.




Troubleshooting Tips 



If after performing the repair your TV still has a problem check the following.

1) Wires - Double check to make sure you plugged back every wire, connector, etc. This is the most common mistake. It is very easy to miss a wire especialy if it is hidden are hard to see. Don't assume that you did not miss one.











We value your feedback. Please let us know if the above kit and instuctions helped resolve your TV problem. Also, any feedback on how we can improve our kits, instuctions, or website is always appreciated.













Last Updated on Thursday, 18 April 2013 10:51