CRT TV Repair- Flyback Replaced
This LG Flatron CRT TV, which is about ten years old, unopened for any service was brought to me with a complaint that it is dead. Unfortunately the label showing the model was torn and so I could not make it out!
After opening the cover and doing a thorough cleaning inside of the cabinet and back cover and on the Main Board, I brought the TV to my workshop desk in dismantled condition. On inspection of the main board, I could not see any dry solder. Checked ESR of electrolytic capacitors. Checked SMPS transformers and FBT (Flyback Transformer or LOT – Line output Transformer) using Blue Ring Tester. All these tests were ok. So, disconnected the jumper wire that goes to FBT and connected a 100W bulb and checked whether the power supply is working. It was working showing a reading of 110V DC. So far so good! Also checked the high voltage fixed capacitors around the FBT area, by removing one leg and reading the value. These were also ok.
Connected the board to the CRT, and switched on. The TV was dead! So checked the B+ voltage. It was zero. Switched off and switched on. The B+ was getting dropped immediately after switch on. The STR driven SMPS power supply had automatic switch off, when current drawn by the load is more. Checked the Vertical IC as well as the yoke for any shorts. None! The HOT (Horizontal Output Transistor) Transistor D1803 was also ok. The only suspect then is the FBT, though it was showing ok in primary winding with Blue Ring Test. So, removed the FBT:
Got an exact replacement and fit the same and switched on. The TV started working once again.
The picture clarity was also good. There was no need for any adjustment of whatsoever! Look at the result below:
The pleasant surprises were (1) Absolutely no dry solder (2) Absolutely no bad capacitor (3) There was no need for replacement of any of the components except the LOT – A rarity indeed! Even the fixed high voltage capacitors were showing correct reading. This CTV was using TDA9340 series instead of TDA9381 series introduced later. A job done without much complications!
This article was prepared for you by Parasuraman Subramanian from India. He is 66 years old and has more than 30 years’ experience in handling antiques equipment Valve Radio, Amps, Reel Tape Recorders and currently studying latest techs classes conduct by Kerala State Electronics Technicians’ Association. He was a BBA graduate, retired as MD of a USA company.
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You may check on his previous repair article below:
June 29, 2016 at 4:00 pm
thank you for sharing
June 29, 2016 at 6:58 pm
i has a sharp tv 29L-FGIL MODEL NO THE HIGH VOLTAGE RISE AND HAS TO BE SHUT DOWN ITRY SEVERAL REGULATOR BUT THR SAME THING HAPPEN ICHANGE EVERY THING THAT NEED TO BE CHANGED BUT THE REGULATOR NOT CONTROLLING THE HIGH VOLTAGE
June 29, 2016 at 7:04 pm
NOW THE REGULATOR SAPPOSE TO CONTROL THE HIGH VOLTAGE 160V IS RISING AND BLOW UP THE CAPACITOR IN THE DC CIRCUITI CHANGE THE TRIAC I CHANGE THE OPTO INSULATOR T CHANGE THE REGULATOR STRW6556 WITH NEW ONES BUT IT REMAIN THE SAME SO I GIVE UP
July 1, 2016 at 10:45 am
The problems are on the load and not on power supply. Isolate 160V going to FBT (Flyback Transformer), connect a 100W bulb as load in place of FBT, switch on. If the bulb stays lit, the power supply is OK. Problem is then in FBT section. Check deflection Transistor, horizontal deflection circuits, vertical IC and yoke. Pl buy book on CRT TV Repair guide for more details. Pl take care while handling very high voltages. All the best!
June 29, 2016 at 7:02 pm
Good job, Parasuraman.
June 29, 2016 at 7:03 pm
your articles are always great to read...keep them coming!
Albert van Bemmelen
June 29, 2016 at 8:57 pm
There is no better Expert for these kind of repairs! Thank you Parasuraman for another great repair.
June 29, 2016 at 9:51 pm
June 29, 2016 at 10:05 pm
Hi chatterpaul persaud try to fix an universal power supply or a power modulator, To replace the fault one.
June 30, 2016 at 6:12 pm
Good job sir Parshuram. I have a salora 14 inch crt tv the electrician video card chip is bad need to replace it.but he did not get the replacement due to non availability.he said get e new circuit board.what are the cost of circuit board. Or will I get video card ship.plz reply
July 1, 2016 at 10:47 am
Sorry, I am not able to make out what your problem is.
June 30, 2016 at 6:15 pm
I even have akai crt tv 29 inch it had sparks in fat so I changed with a new one when if put all the fitting together the tv turned out with front light but when I turned on the remote the tv red light went off.after that the tv is not working.plz help
July 2, 2016 at 11:04 am
Sorry, I am not able to make out what your problem is.
suranga bandara, Suranga Electronics
July 1, 2016 at 3:24 pm
Hi. Mr-Parasuraman Subramanian,
This is Common Fault for This TV Brand.
i have stand by 3 or 4 Fly backs in my shop Stock.
Thanks and Great Your Article.
July 1, 2016 at 8:07 pm
Good Job! Sir,
July 4, 2016 at 3:29 am
Good job sir. I like the detailed notes of yours
July 8, 2016 at 10:42 pm
This a good trouble shooting! Thanks a lot and I have really got something.
July 10, 2016 at 11:08 pm
Hello thanks for sharing I have a toshiba crt tv that turns on showing the red led light in the front indicating switch on but there is nothing on the screen and no sound what could be the culprit as I have checked the board and can't figure it out
July 13, 2016 at 1:34 am
Pl check Secondary high voltage like 110 to 140V (depends on size of tube and circuit). If you are getting it, the problem is on deflection side.I suggest you buy Justine Young's and Kimathy's books on CRT repair, which are very, very helpful!
July 16, 2016 at 6:11 pm
Hello sir I was received one PCB from Castamar, in that board 9n60 MOSFET Wes shorted,,,,now I don't have 9n60 MOSFET,,,, which MOSFET I can use in this place I mean any other ,,,,,pls reply me.
July 27, 2016 at 6:20 am
9N60 is N channel mosfet. As per datasheet, 600V, 8.5A, 1 Ohm resistance. You have to check a matching mosfet online by looking through data sheets. Just type N Channel Mosfet 600V, 8.5A, 1 Ohm in Google. You may bump into many matches.
January 20, 2018 at 9:45 pm
Hello sir, may be you can help me locate a datasheet FBT QQH0137-001 of JVC A-21L11 PIN NO. VOLTAGE.
April 15, 2020 at 11:09 pm
hallo.i have crt 17"that have problem in power supply along the fuse when tuned on,always cuts the fuse.what could be tr
February 24, 2021 at 8:49 pm
Hello, I have just opened up an LG Flatron CRT tv. When I switch it on with a remote, the red power light becomes dim and I can hear the monitor crackles then immediately after few seconds it turns off with the power light shining bright red. Inside the cathode gun burns orange then turns off.
February 20, 2022 at 10:12 am
mine is a tik tik sound on lg 29 inch crt tv. What could be the problem sir.