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I have LG TV chassis cp79b it's problem fly back output voltage did not shown in 200v point of the fly back.

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6ya6ya
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Posted on Jan 02, 2017

TODDAS
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SOURCE: Helo sir, i have a L.G T.V. Model No kf-20p32...

ARE YOU USING A 2SD OR 2SC, CK 1MIC CAP if shorts imediatley bad flyback

Posted on Oct 02, 2012

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SOURCE: lg crt 29 inch tv wont start

The frame amplifier, like the line amplifier, will not work if there is no output from the oscillators for them to amplify.

Early 405 line sets didn't have a frame oscillator as they used the sine wave from the AC mains but I believe the later sets needed a frame oscillator and a sync signal from the rf demodulator to prevent instability.

Transistors rarely fail by themselves and it is often external factors that cause them to overheat and fail and an essential part of the repair process is discovering what factors caused the initial problem. Modern circuits use a lot of multi-transistor dc coupled stages and it is often the bias of an earlier stage that is the culprit.

The frame output transformer is usually very robust and much less likely to fail than a line output transformer. I suggest you ensure the correct operation of the oscillators before going any further.

Posted on Aug 30, 2016

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1 Answer

Power supply input volt are shown in fly back but output volt 200 are not shown in fly back.Please send what's reasons?


Check and replace damaged component/s at its horizontal scan output section circuit. Check the LOT (Line Output Transformer) too for damage. Replace the horizontal scan output transistor. Check the input voltage to LOT. If the voltage is absent check the feeder resistor; if any. If you wish to get some details; check the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/ Type in this key phrase " my service table today " in the search box at the top right of the the home page, to get gathered some pages which has the details of practical experiences of the author of that site. The search result will display about 20 Nos of related posts. Press the "All posts" at the bottom of the list, then you can select them one by one.

Dec 31, 2016 | Televison & Video

1 Answer

In LG 21" CTV, there is no raster on screen and sound is normal. When increasing screen of FBT only plain raster with retrace lines are appeared. when measuring voltage at cathode of CRT, picture apears...


Hi
Please try testing each voltage of RGB output in the small pcb attached to the CRT. If one of these voltages is missing (they are tipically almost of the same value), replace its output transistor. If all voltages are present, but very high (above 180V), please check the filter capacitor in the RGB supply voltage line near the flyback transformer (47uF/150/200V) by replacing it. It is cheap.
Please be careful when dealing with high voltage section of a tv set as capacitors may store a letal voltage. So disconnect the set from main and discharge any capacitor before dessoldering it.


If this helps you, I shall be glad.

Sully

Sep 26, 2013 | LG Televison & Video

1 Answer

I was having video problem on my crt sony kv-g21p2. audio is fine and 1000volt is not producing but 115 volt is producing and i have replaced new fbt but still the same


good day since you have been already replaced the fly back transformer as you said so meaning the problem is not the FBT. any way here are some of my recommendation to isolate the problem .
  1. unplug the tv unit and then unscrew to open the back cover and gain access the crt chassis.
  2. now with use of flat screw driver remove the anode cap of fly back transformer make sure you discharge first for your safety.how are you going to discharge the voltage,get single wire then flat screw driver now strip one end of the wire and tie it to the flat screw driver the other end of the wire splice at the chassis ground of picture tube. and then insert the end portion of the flat screw driver to the anode cap to discharge the voltage left. you can now pull out the anode cap.
  3. by this time you will turn on the tv unit place the anode cap in a safe position not to damage the board be careful its a high voltage. plug the power cord and turn on then observed if their is an arching at the anode cap usually a blue color just to know if the high voltage is present.
  4. if their is a high voltage that means horizontal output transistor is good thats why the fly back transformer is on. your next step is to check the secondary voltage of fly back transformer with the use of digital tester or even an analog tester to know why their is no 1000v. check bad fusible resistor near the fly back transformer usually a 22ohms value this is where the 1000v pass through going to chroma board or video board. if open or no resistance pull out the said part and then replace with the same rating value.check also shorted diode connected to the resistor sometimes it was the cause why the resistor get bad.
  5. after you replaced defective part insert again the anode cap for testing once again be careful.
  6. now turn on again the tv unit then observed if their is a video on the screen check also the heater voltage at the chroma board if present usually about 2Vac something you will also noticed their is a light at the neck of the picture tube.
  7. if the 1000V is present the heater and the B+ supply voltage i'm sure the video will come out. i hope those steps that i give to you will help to fix your problem thanks for choosing the fixya if you have further question i'm glad to help you.

May 31, 2011 | Televison & Video

1 Answer

Tv will not come on


HELLO. it sounds like it could be a couple of things why your set will not come on. 1. you could have a blown fuse.on the chassis. 2. you could have a bad power supplly transformer. 3. you could have a bad horizontal output transistor and a bad fly back transformer. it could be one of them or both of them as well as a blown fuse. because the fuse is blown from the horizontal output transistor burning out or the fly back transformer burning up. check and see if you have a burnt fuse, the size iof the fuse will be 5 amp to 6.3 amp fuse on the chassis right inside where the 110 ac cord comes in and hooks to the chassis. the fuse should be right there, look for it. hope this helps you"GOOD LUCK"

Aug 09, 2008 | Televison & Video

1 Answer

No power.its plugged into the outlet and it works. red power buttom not on tv


HELLO. it sounds like it could be a couple of things why your set will not come on. 1. you could have a blown fuse.on the chassis. 2. you could have a bad power supplly transformer. 3. you could have a bad horizontal output transistor and a bad fly back transformer. it could be one of them or both of them as well as a blown fuse. because the fuse is blown from the horizontal output transistor burning out or the fly back transformer burning up. check and see if you have a burnt fuse, the size iof the fuse will be 5 amp to 6.3 amp fuse on the chassis right inside where the 110 ac cord comes in and hooks to the chassis. the fuse should be right there, look for it. hope this helps you"GOOD LUCK"

Aug 09, 2008 | Televison & Video

1 Answer

Tv screen went blank. When I unplug and plug back in I here a hissing Lg 42 flatron plus 6 years old.


do you have heater voltage because if you are hearing high voltage you may need to replace a resistor and capacitor in the 200v circuit or you could possibly have a anode not seated right arcing on somthing or a bad flyback

Jun 11, 2008 | LG Televison & Video

1 Answer

POWERS DOWN AFTER 4 SEC


crt beam current too high causing shutdown as you know. Check cathode voltage of each cathode, normal levels depend on picture is around 130-150V. Missing 200V to crt board. Screen voltage problem normal 300-500V. Flyback or bad crt. ABL circuit problem. Jungle IC.

Oct 29, 2007 | Philips Magnavox TP3285C 32" TV

1 Answer

Lg 5552 v set is dead


try to resolder all points in fbt including fly back trans itself area also resolder the crt pcb area i had the same problem the reason was cold soders also put a good 2sc5297 for hor out.

Dec 02, 2006 | LG Studioworks 552V 15" CRT Monitor

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