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
Albert van Bemmelen
September 3, 2021 at 12:51 pm
Interesting that the cpu copied the default data to the new 'empty' 24C16 SMD IC after which the tv was accessible as new. I wish that I was so lucky with a LG GDR-8163B DVD-ROM drive I was working on. Sadly the tsop32 29F002 (or a used 39SFxxx 'Bios') eeprom got destructively flashed by the orginal LG IDE/PATA upgrade flash program and externally re-programming this eeprom failed. Also because there is no external existing bin/hex data file that can easily be used to flash the chip back to a working original with. Because that 'rom' file is packed into the flashing program that killed the drive in the first place. So bad lick with Lucky Goldstar (LG)! Also expensive tsop32 to dip adapters are needed to read or write to these tsop32 (14x8 mm or 20 x 8 mm) smd eeproms which makes this a very difficult task to fix. And the free and small "Resource Hacker" program may help to examine those packed exe and dll windows flashing programs in search for the hidden bin/hex files.
September 3, 2021 at 5:24 pm
Many thanks for your comments and expert experiences shared!
September 3, 2021 at 5:22 pm
"Mission accomplished very successfully with minimal efforts"
I think you are being too modest, Parasuraman - that looks like a very technical repair!
September 3, 2021 at 10:14 pm
Compared to the struggles that I had to undergo in various other CRT TV repairs, this was easier! That's why I said 'minimal efforts!' Many thanks for your comments, dear friend and the concern shown!
September 3, 2021 at 9:51 pm
Good job!! Interesting set of problems. I am always curious about the failures; which part started the chain reaction of failures? Was it excess dirt around the pins of a part? Or just outright failure of one part? Dry solder joints causing to much stress or heat? Just wondering.
Thank you for all of you postings!!
September 4, 2021 at 4:11 pm
The failure could be due to sudden voltage surge. The customer reported a sudden sound heard from TV and it went dead, as mentioned in first line. Many thanks for your comments and analysis!
September 3, 2021 at 11:17 pm
Good job there. Very enlightening and interesting expose' . Keep it up.
September 4, 2021 at 4:12 pm
Many thanks for your comments!
September 3, 2021 at 11:26 pm
Great job there.
September 4, 2021 at 4:13 pm
Many thanks for your comments!
September 6, 2021 at 3:47 pm
Very nice repair work sir.I just wish if you can help me solve my own problem. Lg CRT TV with model number 21FS6RLD power led is on but TV with not start up.checked the output voltages,the b+ is 93v instead of 126v,the 14v is 8.9v and the 6.5v is showing 5.2v.one capacitor along the b+ line was bad .l replaced it,and check other caps on that line which show ERS are OK.please how can I go about it again. I really want to fix this TV myself.thanks
September 7, 2021 at 12:09 am
There are many reasons for it. First check feed back circuit around opto-coupler, and if it has SE series regulator, check that too. Unless proper voltage is generated, FBT will not get switched on. Disconnect the jumper/resistor that takes B+ to FBT. Connect a 100W bulb load and check whether power supply is stable. If on/off is controlled by uController, just disconnect the control and see. If power supply is ok, Check whether is LOT is loading because of some short secondary loads like Vertical section or LOT itself is defective. Good Luck!
September 17, 2021 at 6:03 am
Thanks sir for your advice. I disconnected the jumper wire to the fbt and connected 100w bulb,the build light bright steadily but the voltage is still 98v on that line(b+) instead of 126v.please where should look at next.I also disolder out the 5v voltage regulator k4431 to the input of the octocopler and the standby light went off.Resolder it back in and the standby light remain steady.please am ready to learn from you sir .thanks
Michel Seya Ndala
October 9, 2021 at 4:52 pm
Hi Efijemueh Philip; I'm just reading what you are looking for and decided to tell you that I encountered the same problem and solved it. So Can I help you or you have done already ?
September 7, 2021 at 3:52 pm
Good repair! sir,
now a days repairing is challenging because manufacturers are putting Programmable IC's even PWM IC also.
September 8, 2021 at 11:16 pm
Yes, very true! Many thanks for your comments, dear Yogesh!
September 8, 2021 at 2:37 pm
yes, I hate that when it happens. you work on the tv to get it to work then end up in a password finding situaton and the child lock is on but dispite all that the TV was up and running again. thanks for sharing.
September 8, 2021 at 11:19 pm
We, electronic technicians should take all problems we face as opportunities to learn! Our progress depends on that. There is nothing to hate! All situations are alike for a technician. Attack, attack and resolve is the marching slogan for us! Many thanks for your comments, dear friend!
March 18, 2022 at 9:51 pm
Onida ultrraslim enter key problem I check change 24c32 same ic change to tv on hight and weith size both long type no adjustment the hight or vsize memory original enter key problem I chek og romete only stanby only on no other open and no service key open 5963kw