Standby LED Blinking Problem in TCL TV Solved
Customer complaint that this TCL CRT TV standby power LED always blinks and without picture. For your information standby power LED blinks can be caused by few reasons such as unstable dc output voltage from the power supply, component’s leaked or shorted at secondary side, memory IC firmware corrupted, main power supply primary side itself have problem and etc.
The first thing I did after opening the TV cover was to check for any dry joints in the circuit board. All solder joints seems to be intact and there were no bulged e-caps either. Below photo showing the solder joints of the TV circuit board:
Next test I checked on the B+ input DC supply voltage of the flyback transformer pin. A good working TV should have about 110VDC (depending on the size of the TV) but this point measured 92.8 only. The horizontal output transistor and surrounding components checked to be good thus I suspect the flyback transformer could be the culprit.
In order to confirm that indeed the flyback is the caused of the problem I soldered a 100 Watt light bulb between the B+ input and cold ground-look at the photo below:
When I powered it On, I got about 105.1 VDC indicated the power supply was good and the problem was in the flyback that drawn too much current causing the B+ voltage to drop.
I got a new flyback and the part number was BSC-25-0230Z and soldered it to the board.
I powered the TV On and the voltage that I got was 105.2 volt and this had proven the flyback transformer indeed was the culprit.
I cleaned the circuit board with BCP chemical after I had installed the flyback transformer.
The circuit board looked new!
Once all the parts were fixed I powered On the TV and the display appeared indicated the job was done.
Conclusion- In the above repair case it was only the flyback transformer at fault. If it is not the flyback then I need to check on other area possible firmware problem if the memory ICs are receiving good DC voltage from the power supply. All the best to you and hope to see you again.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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https://jestineyong.com/linear-transformer-primary-winding-open/
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Graeme
December 16, 2020 at 8:50 pm
Good to see a methodical electronic approach rather that just the eye ball approach which has been showed very often recently(not that there is anything wrong with the eyeball approach).
Sailesh
December 17, 2020 at 11:59 am
Superb... troubleshooting...
Waleed Rishmawi
December 16, 2020 at 9:01 pm
There is still fly back transformers left? In my country they can not be found any more and CRT tv do not exist. Very interesting repair thanks for sharing
Andrew F. Ali
December 16, 2020 at 10:34 pm
We have moved from CRT TVs to LCD and LED TVs in my country. But I do remember my CRT TV repair days. Good job!!!
Albert van Bemmelen
December 17, 2020 at 12:44 am
Incredible that these FBT's are still available. Also in my country they are completely obsolete these days. Like those CRT TVs now are. Sadly also 3D TVs are no longer sold. And sadly the holographic projection TV still takes more time before it finally arrives.
Tayo
December 17, 2020 at 2:32 am
I learned something new and I really appreciate it Suranga. Thank you!
Nigel
December 17, 2020 at 1:28 pm
I so do recall my dad working on CRT TV some years back(this got me interested in electronics) nowadays we pass by the bins to see loads of CRT sets disposed off because buying a LCD/LED TV is cheaper then getting parts abroad plus not to mention repair work. Thanks Mr.Bandara for the article for have learnt something new.
Parasuraman S
December 17, 2020 at 1:30 pm
Good and informative article! Thanks for sharing!
Lynn Blakely
December 18, 2020 at 4:31 am
Suranga: You performed an excellent repair, thanks for the good explanation. The commentators are correct in many country's crt tv repair is no longer being done.
Humberto
December 18, 2020 at 12:57 pm
Good article and excellent explanations.
ivan
December 20, 2020 at 6:39 pm
thanks or this lesson sir , 100wat bulb acted as a dummy load meaning
Yogesh Panchal
December 20, 2020 at 11:05 pm
Perfect fault finding! Suranga.