21 Inch Hotpoint CRT Television Dead Now Repaired
I received this television from a customer and the complaint was dead but Power On led is lit and red in colour. This means the television is getting power on the secondary side and also the microprocessor is powered but getting “all is not well” feedback and hence going into standby mode.
I hit the menu button and the television fired and I was able to see a faint line across the screen before the television went into standby again.
With this I got a clue that the problem is on the vertical circuit, therefore I can now open the set and do further testing on the vertical circuit.
I opened the set and before removing the board (Hv cap) I had to make sure there is no high voltage charge still held on the anode cap and this I did using the trick above.
I scanned around the vertical circuit looking for any suspects and was not able to pick any suspicious looking component.
So I decided to start checking all the capacitors around the circuit and I was able to pick one capacitor C451 (100uF/35V) whose ESR was very high as you can below.
I thought to myself that it is only culprit and therefore replaced it and again applied power and to my surprise the problem remained the same, no improvement at all. I pulled my meter and tested all voltages to the vertical i.c and I noted all pins had over 30 dc volts except the ground.
This is strange and I suspected the vertical i.c must be having a problem and therefore I replaced it too. I applied the power once again and this time the television came up beautifully but again I was not happy with the final product.
The screen had huge coloured spots as you can see below.
I suspected the posistor and therefore decided to check if it is okay or not. The best test for posistor is by direct replacement whenever you see colour patches on the screen. Usually if a posistor shorts it will blow the fuse and in my cause the fuse was intact and therefore suspected it was open.
When the posistor is open the television will still work but you lose the cleaning function of the degaussing coil which works together with the posistor.
Usually when the posistor is working it gets very hot and in this case I touched the top of the posistor and it was cold and with that I concluded it is open since like I said earlier a shorted posistor will always blow the fuse.
I replaced it with one I found in the junk board and after powering on the screen now crystal clear.
Thank you friends.
Humphrey Kimathi is from Nairobi Kenya and the author of
1) Lcd-Led television repair guide
3) CRT Television repair course and
4) Basic Electronics course.
He is also a blogger at Electronicsrepairmadeasy.com
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https://jestineyong.com/no-power-in-vitron-led-tv-repaired/
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Albert van Bemmelen
September 2, 2019 at 2:56 pm
Well explained crt TV repair from a pro at work! A few weeks ago I dismantled a couple of still perfectly working bigger Philips Color TV's for spare parts (one 25PT4655/00 75W TV). Because they simply are way too big to keep all, why I only kept 2 smaller crt ones, and a couple of old perfectly working crt type monitors for CVBS/FBAS video and C64/128/Amiga computers. Recently it became knowledge that Philips with other crt TV manufacturers had engaged in a price-fixing scheme to drive up the cost of CRTs.
The lawsuit alleges Philips and other CRT manufacturers, including LG, Panasonic, Hitachi, Chungwha, Toshiba and Samsung, engaged in a price-fixing scheme to drive up the cost of CRTs from 1995 to 2007. During those 12 years, the price-fixing conspiracy caused millions of Washington consumers to be overcharged for their CRT televisions and computer monitors. And the same happened with CRT TV buyers in my country.
Yogesh Panchal
September 2, 2019 at 3:42 pm
Good Quick Fix Sir,
Parasuraman S
September 2, 2019 at 6:15 pm
Good job! Learnt about the role of posistor this way too, now only! I will take care of it in future! A good and useful tip! Job well done. It is surprising that the TV was getting on instead of standby, when the Vertical IC was short!
Sylvester Ongaya Takisi
September 3, 2019 at 2:43 pm
Well done brother. Article was a reinforcement of what I have learned from your book CRT repair. Agood learning experience for me.
Waleed Rishmawi
September 3, 2019 at 1:44 pm
congratulations on a job well done. have a blessed day
Tito Kanshulu
September 6, 2019 at 7:23 pm
Congrats brother Humphrey.Your writings are always well shined and l like them. It's a good step by step. Keep it up.
Edwin
August 22, 2021 at 5:31 am
Good job but why remove the crt anode cap to test the vertical stage?
Its not necessary