Tip & How-To about Televison & Video
Your TV is dead or perhaps the turn on relay clicks and immediately clicks again, followed by your standby light blinking a specific code. For each TV the code is different. To find out your code google "(your brand name) error codes". This should return the listing of codes for your unit. Check the code to see if it is the high voltage section with the problem.
The hardest working section of any TV is the high voltage section. This does not apply to flat screens and DLPs only CRT projection units and conventional direct view units. The flyback gets hot and is made of many windings of very thin copper wire which is only shellacked to insulate it. Over time the windings coating will break down and the windings will short together. This can happen in as little as several years. Once shorted, there is less resistance, and the current being pushed through the flyback increases. This overloads the Horizontal Output Transistor which gets hot and fails. This in turn causes the low voltage power supply to detect the overload and not allow the unit to start up, also sending the appropriate error code blinks.
The flyback is generally near the rear of the unit and is cylindrical with a large rubber wire, or wires, if a projection set, coming out of it and going to a rubber cup on the CRT or CRTs if projection. Near the flyback will be a large heat sink with a large transistor mounted to it. With the set unplugged check the large transistor or HOT, with a DMM on diode scale for resistance. The leads of the HOT should be marked on the circuit board (C= collector, B=base,E=emittter). If the HOT has 0 resistance between all the leads it is shorted and you need to replace both it and the flyback. If it is good it will have infinite resistance one way and 400 to 700 ohms with the leads reversed between either the base/emitter or the base/collector. In circuit tests between the collector and emitter will show a short because you are reading through the flyback transformer winding. You would have to take the HOT out of the circuit to test this double junction but if the other two junctions test as I have listed them, odds are the transistor is good. If all junctions test shorted the HOT is bad and needs replaced.
You should be able to obtain both parts, if you need both, at http://www.encompass.com or http://www.shopjimmy.com . Unsolder both parts and remove them from the board. This will require a large soldering iron, solder wick and a solder ******. Be careful not to damage the board. When installing the new HOT be sure to clean off the heat sink and apply new heat sink compound, if the old HOT was mounted with heat sink compound (not all transistors are), available from the parts supplier. The flyback also will have two additional wires to remove and replace. One goes to the CRT board and may plug into a plastic box on the CRT jack or be soldered into the board depending on the model. This process should be self explanatory if you study it a while.
Depending on whether you have a projection TV or a Direct View TV the procedure is a little different. I will describe the procedure for a direct view TV first.
The 2nd anode lead (large red rubber wire going to the CRT) is plugged into the CRT and may have 48 kilo volts on it! Discharge the potential to the ground strap (bare wire going around the CRT) using an insulated screwdriver and a wire with gator clips on each end. Clip one end of the wire to the ground strap around the CRT and the other to the screwdriver. Slide the tip of the screwdriver carefully under the boot on the CRT where the 2nd anode is attached. If the CRT was storing power there will be a spark and loud snap when you make contact. Once discharged the tube is safe. Pull back the rubber boot and remove the wire from the hole in the tube. Install the new flyback wire. Solder the new flyback to the board reassemble everything and turn on. If you were successful the unit will start. You will need to set the focus and screen drive using the two potentiometers on the back of the flyback. Top is focus, bottom screen drive. Turn up the screen drive to get a picture. Tune to a channel with text. Turn focus to get the sharpest image. Generally even if you have bad vision you can focus the set by making the image pixels stand out. If you tune through the range of focus you will see what I mean. Tune to a channel which has both black and white in large amounts. Turn up screen drive until the black just begins to light up or starts looking gray then back it off slightly and you should be done with the unit. Be careful while adjusting the flyback as the set will have lethal voltages in it.
Now for the flyback on a projection TV. It will have 4 large rubber wires coming out of it. If the new one came with wires they should be removed at the HV divider block (located at the front of the set normally, just follow the wires to their end) if not they should be removed at the flyback. To remove at the flyback, which is the most common hookup, slide the rubber boot off the post and using needle nose pliers pry the cable out. It should have a bare end which connects to a clip at the bottom of the new unit. Do them one at a time to avoid getting them wrong. When done you will have to adjust the focus and screen drive but it will be on a separate box called the HV divider block usually near the front of the unit behind the grill. Same process as listed above for the direct view set except there are three contols for focus and three for screen drive (red,green,blue). If your unit still does not run you may also have to replace the HV divider block. All safety rules apply here also.
That should conclude the repair and if successful your set will work. If the unit still does not work go to my tip on troubleshooting at http://www.fixya.com/support/r4425277-basic_direct_view_tv_troubleshooting which explains the basic troubleshooting method to find any problems in standard televisions.
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