Track Served As A Fuse To Save CRT TV From Lightning
This Sharp 20” CRT TV was brought to me in dead condition, after a lightning strike. As usual, my first job was to clean up the in and out of TV, which I did. Removed the PCB after discharging the anode of CRT and disconnecting yoke, Degaussing coil, front panel, speakers and Earth.
On inspection, I noticed that a track has got cut on the SMPS, cutting off the B+ supply.
I restored it. Looked for any other burst, defective components and did not find any. Disconnected the B+ line to LOT /FBT (Line Output Transformer – Flyback Transformer) Loaded a 100W Bulb in its place and applied power through a 200W Bulb. The output was perfectly showing 110V, to my amazement and relief!
Disconnected the Power Supply, discharged the Tank Capacitor of SMPS and restored the jumper to FBT. Loaded the PCB to the CRT and checked! It showed dull and defocused raster.
As I know that such a thing can happen due to dry solder on the Focus Pin of CRT, disconnected the Power, and removed the CRT PCB and checked the Focus supply pin and indeed it was a bad solder. Touched it up and reconnected the CRT PCB and switched on. Now the raster was good and the blue screen showed correctly. Applied a Video and tested the TV for many hours and did not find any problems.
After having satisfied that the CRT is back to life, returned it to the customer. A simple lucky job, which too got added to my satisfaction bag, as some sort of bonus!
This article was prepared for you by Parasuraman Subramanian from India. He is 69 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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You may check on his previous repair article below:
https://jestineyong.com/unsatisfactory-attempt-to-restore-panel-problem-in-sony-lcd-tv/
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Waleed Rishmawi
March 28, 2020 at 1:50 pm
Good job on the repair. Have a blessed day my friend.
Parasuraman S
March 28, 2020 at 9:55 pm
Thanks for your continued support! May God bless you!
Albert van Bemmelen
March 28, 2020 at 3:15 pm
These things are only easy with an experienced tv repair master at work!
Parasuraman S
March 28, 2020 at 9:57 pm
By experience, our brain gets tuned up to catch trouble spots and this is the case with almost all such technicians like you. Many thanks for your continued support! It values very much to me!
Mark
March 28, 2020 at 4:21 pm
Well done Parasuraman,
I am working on a Smart TV at the moment that has had a burnt track similar to yours where none of the fuses, varistor or thermister failed.
Strange, but true!
Parasuraman S
March 29, 2020 at 7:33 am
Yes, perhaps the speed at which the damage happens, bypasses the protection, which could be designed to withstand the surge for a few microseconds. (I mean slow blow fuses)
Robert Calk Jr.
March 28, 2020 at 6:31 pm
Nice work, Parasuraman!
Parasuraman S
March 29, 2020 at 7:34 am
Many thanks!
Yogesh Panchal
March 29, 2020 at 3:38 pm
By years of hands-on practice automatically our sense will help us to reach the culprit area.
Good Job! Sir
Parasuraman S
April 2, 2020 at 7:10 am
Very true!
Humberto
April 1, 2020 at 2:18 am
Congratulations for sharing your expertisings with us.
Parasuraman S
April 2, 2020 at 7:10 am
Many thanks!
DOĞAN
April 5, 2020 at 8:23 pm
Hail from Turkey.
I follow all the time.
Parasuraman S
June 13, 2020 at 11:28 pm
Many thanks!
Machiding
April 7, 2020 at 6:27 pm
My tv the sreen is very dark but at night I can watch any movie or any thing I like but during day light I can't whatch tv
Parasuraman S
June 13, 2020 at 11:36 pm
So, what do you propose to do? Did you try adjusting the brightness? What type of TV is it? LCD/LED or CRT?