Question about RCA HD52W140 52" Rear Projection Television
Much like many of the other posts here, my RCA tv will not turn on. I don't know any history of this television, as it was handed to me to see if I could fix. The report was, it was working fine and then one morning he turned it on and it was on for a few seconds and then "turned off" and would never turn back on. He did not recall hearing any strange sounds or smelling any smoke, it just quit.
There is no activity on the set at all. When plugged in there are no standby lights or any other sights or sounds. When the power button is pressed, nothing happens.
I have gone through the many posts here, as well as other forums, to try to get some idea of what might be wrong. The vast majority refer to the HV Splitter causing issues including a particular resistor blowing (R14705). I have checked that particular resistor as well as the leads and the traces on the board with a meter and they all seem to be fine. I am not sure how to check the HV splitter without just simply replacing it.
I'd rather not just do trial and error if I can check it to see if there is an issue. Does anyone know how to check the HV splitter for trouble before replacing it? Also, assuming that is not the issue, what other possible issues could be causing the tv to appear completely dead?
Ok first of all the only way the trippler could have caused this was if it shorted, and you would have known if that happened, because of the fire that would have occurred. So let's go back to square one. did you check the primary power supply in the back of the chassis? check it first for a blown fuse. I you can not find that then disconnect the power connection to the high voltage board and secondary power supply (switching power supply) and see if you can get the supply rail to the secondary board up (you will need a schematic to see the voltage values that should be there. Now if that fails to produce results you will have to assume that the secondary power supply is the culprit (it usually is). The funny part about this is the one component no one ever tells you to test is the one you should test all of the time and that is the IHVT (Integrated High Voltage Transformer) some folks refer to it as the "flyback" transformer. Now one of the biggest problems happens at this point there are three tests that you have to run the equipment needed is a s follows:
1) an oscilloscope
2) Universal Signal Analyzer/Generator with Ring Test ports
3) A capacitance meter or a LCR 103 (I prefer the LCR103)
4) an ohmmeter
Now here is what you need to do to test the IHVT
1) Remove the IHVT from the circuit board (desolder it)
2) Remove the HV cable clamp (holding the HV cable to the base of the IHVT)
3) (Test 1) Perform a resistance test between the posts of the IHVT looking at the schematic to see which posts are wired to each other. (now this test is only good for pointing out open coil windings not shorted coil windings) if this test passes (no opens) go to test 2
4) (Test 2) perform a ring test of the IHVT. Now this is why you need the Signal Generator with ring test ports. Connect the cable from the ring test ports to the primary side of the transformer, see the schematic to determine the primary os the transformer (the side connected to (actually between) the Horizontal Output transistor and the power supply. turn the ring test actuator fully counterclockwise, turn the test selector to ring test and slowly turn the ring test actuator clockwise until the screen reads greater then 10 rings, if ten rings can not be achieved then the IHVT has a short in it and should be considered as bad and in need of replacement. if this test passes go to test 3
5) (Test 3) The last test is the capacitance test. This test is a test of the internal capacitance of the IHVT. This is measured from the HV anode of the transformer to the ground post of the transformer. connect the negative end of the capacitance meter to the ground post of the transformer and the connect the positive end of the capacitance meter to the anode of the IHVT (this is the end that the cable was removed from, You will have to use a probe with a wire attachment to it to make contact with the anode connection in the IHVT. Once that is done the capacitance meter should read around 2.7nf or above. A reading of .3nf means the capacitor is open. Note: However certain flybacks may have the value of 4.5nf, 6nf and 7.2nf and sometimes the internal capacitor pin is connected to circuits (feedback) instead of ground, so be aware of this when testing. If this test passes then the problem is not the IHVT.
However if any of these test fail then the IHVT is to be considered as bad.
Now if the IHVT is good, then you will have to test the following components and their respective circuits:
The Horizontal Output Transistor, The Switching power supply MOSFET, The switching power supply transformer (perform ring test just like the IHVT), and pay special attention to the capacitor on the 6 volt rail (This capacitor is known to go bad often) as seen on the circuit board, The schematic will have all of the part location numbers as seen on the board.
This is a logical start as opposed to the shotgun approach a lot of forums seem to lead to. Let me know if this helps you.
Posted on Jul 24, 2008
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Posted on Jan 02, 2017
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