SMPS Transformer Failed In OPTONICA CS-5151A CRT TV
MAKE AND MOEL NO: OPTONICA CS 5151A CRT TV MADE BY KALYANI SHARP IN INDIA
COMPLAINT REPORTED: DEAD
HISTORY: This is a lightning affected CRT TV, board of which was brought to me by one of my Techie Friends, as he could not solve the problem.
TROUBLESHOOTING AND RECTIFICATION DONE: Cleaned the board thoroughly, which had even gecko eggs inside cozy areas. Disconnected the B+ rail to the FBT, loaded a 100W bulb and checked. There was no power. Discharged the tank capacitor and checked SMPS transformer with Ring Tester. Only one LED was lit, indicating problems in the primary or secondary. Checked the components in the primary and secondary. Found one Diode short in the primary and value of a fixed capacitor changed. So replaced these. Again checked with Ring Tester and got the same result. Checked all components in the secondary and did not find anything wrong. On suspicion, I removed the SMPS transformer and used my SMPS Tx tester made by me using a three pin module for such purposes. There was no output. Disconnected and checked the Tx with the Ring Tester, which indicated same like before. So, this was a case of SMPS Tx failure, which is very rare. Hunted for an equivalent one with my Techie friends as these were no longer available in the market and got one. Put that Tx and switched on. The bulb load lit indicating that B+ was working. So, switched off, discharged the Tank capacitor again, reconnected the B+ rail to the FBT and loaded the board on to my CRT Tube, which I have for testing boards. Switched on and found the blue screen, adjusted the screen and focus voltages for its peak levels.
Then applied a video signal, but nothing was coming. So, looked for the reason at the rear of the board, and traced a cut track in the input of the video. Joined it with a wire. But still there was no video. Checked the voltages of TDA8362 Croma Ic and found the power supply voltages to be normal, though the output voltages were not as desired. The IC also was getting hot, indicating that it was defective. So, replaced it. Then the TV started working. Discharged the anode wire and tank capacitor, removed the board and replaced all its electrolytic capacitors as a routine maintenance and retouched all the solder joints on the main board and CRT Board. Reconnected the board for testing and found it to be working very well. This is a board which does not have any remote control circuit.
Unfortunately, my techie friend succumbed to the pressure from his customer and went ahead and to fit the TV with a new PCB (China Kit), which ultimately resulted in my adding this board to my stock, bearing the cost of service! What else can we do? I do not blame my friend, as I know how some customers are. They just do not have the patience to wait! Anyhow, I have told my friend that the board is reworked to bring it back to perfect working condition, and should this TV again come for repair, better to put back the original board. Anyhow, I doubt the chance as the new board of China Kit has a remote control. Mission accomplished and satisfaction added, this time with additional cost borne!
HERE ARE SOME PICTURES:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 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/high-voltage-or-lightning-caused-pwm-ic-burst-in-prestige-induction-cooker/
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19 Comments
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Albert van Bemmelen
September 26, 2020 at 2:40 pm
Indeed much work done at personal loss of time and costs because of an inpatient customer! Personally I still haven't had any luck with my 2 Chinese DVB-T replacement boards. And even if I managed to find the right not Chinese firmware to run my receiver board on any LCD screen, it wouldn't receive any TV station as they now all are using the DVB-T2 norm.
Parasuraman S
September 26, 2020 at 5:17 pm
Most of the customers want their TV back one day before they gave it to us! The reason is addiction to watching Serials, Movies and Sports. So, their mind does not accept the 'No TV' situation!
Waleed Rishmawi
September 26, 2020 at 3:16 pm
what a situation? It is not your fault but I think your techie friend should at least pay for your work...there are stuff in my shop for almost a month now waiting for part from china and everyday they call about the repair finally I told them if they are not patient to wait come and get your stuff. finally I got there stuff repaired now they are not calling about the repair and even I called them to come and get the stuff they say they are busy to pick up. so I made a delivery to their house and made them pay for delivery and the repair..some customers are so bad and I am so much fed with these kind of customers.
have a blessed day. good job my friend and I am sorry you had to go through that.
Parasuraman S
September 26, 2020 at 5:18 pm
Yes there are many customers, whose behavior many times comes as a surprise! But we have to put up with it! What else can be done?
Franklin
October 2, 2020 at 2:06 pm
Good day sir. I love your works and I appreciate you so much.
Eric Rice
September 26, 2020 at 9:24 pm
One thing I am curious about, why do you wait till after fault finding to replace the electrolytic caps? I have found it much easier to replace the caps first then start fault finding. This removes the caps as an issue, then being able to concentrate on the other issues as they come up. Am I doing something wrong?
Parasuraman S
September 26, 2020 at 11:42 pm
Good observation! In the preliminary troubleshooting itself we locate faulty components and replace it, which include electrolytic too. Once we ensure that the set works very well, we can handle the rest of the replacements to make the service perfect to the dot!
If we replace all the electrolytic capacitors first and the problem is in the uController or such unavailable part, we would have wasted a lot of our time, money and energy, would we not?
Eric Rice
September 27, 2020 at 7:57 am
You’re right, however in the other repair article for this issue, a great amount of time was wasted looking for a fault when an out of spec cap was the cause, since it passed an ESR test. Obviously there is a trade off, cost of time vs cost of parts. In the sense of just a few caps involved on a circuitboard it maybe cost effective to replace them all first. Just thinking!
Parasuraman S
September 27, 2020 at 7:12 pm
Yes, I agree. But it depends on the type of complaint and the possible causes from our past experiences. We should also bear in mind the readiness of the customer to pay for it.
Eric Rice
September 28, 2020 at 3:09 am
Like you, I always notify the customer before proceeding so that the cost is understood. Learned electronics while in the US Navy many years ago and I now own a small musical amplifier repair shop, and I also manufacture amps as custom builds for musicians. It is just myself, but well enough to keep me busy. Thank you for your comments!
Parasuraman S
September 28, 2020 at 5:22 pm
Vow! That's good to know! All the very best to you!
B. Scott
September 27, 2020 at 12:42 am
That was a lot of parts replaced... I have to ask...how much in U.S. dollars would you estimate this repair actually cost.....I am just curious......Excellent job......
Parasuraman S
September 27, 2020 at 7:15 pm
The cost of this repair in us $ would be around 18-20 $
Imoudu
September 27, 2020 at 5:54 am
The marked B+ pin on FBT is it the B+ rail ?
Thanks.
Parasuraman S
September 27, 2020 at 7:18 pm
Yes, the B+ rail that goes to that pin, and returns to the collector of the Horizontal Output Transistor, which is pulled down by the Transistor to ground at high frequency to generate the oscillation.
babums
September 27, 2020 at 10:13 pm
Sir,
your fault finding way is very excellent,as I am beginner it is very useful article for me.The circuit may please be given to test SMPS transformer out side made by your self.
Yogesh Panchal
September 28, 2020 at 1:27 am
Sir,
Our let go practice make this type of customers more habitual.some time equipment's are non repairable because of unavailability of parts so what about our Time /efforts......always bound customer if he doesn't want to repair the unit after starting the diagnosis process he have to pay minimum diagnosis charges.
Parasuraman S
September 28, 2020 at 9:26 pm
Its my friend's customer. I have borne the cost because of him. Anyhow I got one good working board!
Collins MAMBWE
January 9, 2021 at 7:49 pm
Hello! Please help: How do I tell or test if my FBT is defective on my Hitachi-Fujian TV HFC-14P69 using a DMM? LED is ON but TV is not responding to buttons or remote.