Cracked Fuse, Capacitor, Shorted STR & Diodes Found In ONIDA Ultra Slim CRT TV
This CRT TV model No.CO21SBL300B of Onida make was brought to me stating that a loud bursting noise was heard while watching the TV and it became dead. I opened the TV and subjected it to thorough cleaning. Observed that the Fuse and one Blue 102/2KV Cap in SMPS were burst. Disconnected the board from TV, isolated the FBT (LOT) from B+ supply. On checking, I found that two of the rectifier diodes were short. Replaced the fuse, capacitor and all the four diodes and also the STR as in all probability it would have blown.
Replaced the high voltage electrolytic caps on the secondary, CRT Board and near FBT. Checked ESRS of other caps and found these to be ok. Retouched all points on the power supply section and a few other points found in the secondary, vertical and horizontal section.
Then connected a 100W bulb as load and powered the board. The bulb lit and the voltage also was found ok. Loaded the board back to TV, after restoring the jumper to FBT.
Applied power and got a screen asking for key pass word to open.
The remote control that came with the TV was partially defective and the on/off button was not functional. None of the panel switches worked. According to my techie friends, if child lock is activated the panel switches cannot be operated and we need to have the original remote for switching on and entering to service mode. I asked the customer, who was an auto driver, to buy its remote control. Even after trying from it, this screen did not go and none of the suggested passwords. So the settings had got affected and replacement of the memory IC was the only solution. I used a blank 24C16 SMD IC in place of the one in the TV.
Then when applied power, the TV got on after a few minutes, during which the uController copied the default program files and settings to the blank memory IC. Then applied Video and found the picture quite normal. I replaced the PTC also, as colour patches were seen. The old PTC was found burnt. Adjusted the focus and screen voltages suitably and also the brightness/contrast/ colour/sharpness etc. to a pleasing level. Tried TV for several hours before closing the back cover and drawing a curtain to this CRT TV repair work. The satisfaction very briskly jumped into its collection bag! Mission accomplished very successfully, with minimum efforts. Here are a few pictures to conclude this article:
This article was prepared for you by Parasuraman Subramanian from India. He is 72 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 article on Intermittent Problem In LCR Meter Repaired