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.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous repair article below: