This CRT TV was brought to me by an elderly widow with complaint of not switching on. When I checked it, I noticed the ac cord had burnt at base of cover case. See cover.
I replaced ac cord and powered tv, tv powered on and see what appeared on screen below:
As you can see, it’s a horizontal line. With this I know the problem has to do with vertical circuit. So I removed case cover, clean board and perform visual checking, nothing suspicious. Then decided to do voltage test on the vertical IC pins,(No utc78040).
This IC has 7pins and one of it’s pins was having 0 voltage, so I suspect this IC. I then trace the track of this pin to a diode which was opened (1N4004).
Then I decided to check all components in vertical circuit in which I discovered some e – caps that are high in ESR values, tank e-cap had oxidized, see pictures below:
Then I try to remove IC by desoldering it out, but I got some track damaged as result of lack of experience ( doing this 1st time anyway).
So I replaced IC with LA78040, diode with 1N4007 and also other bad components, also repair damaged tracks pictures below:
Then connect everything together and power on TV.
The video and audio came up load, but picture is blur!!.What a disappointment!!.
So I suspected problem could be with either FBT or crt socket, I check on socket, it’s o.k. In my country, brand new fbt is not available, except those extracted from junk boards which I do not intend to use because it will not last. So the only option I have is to order it online.
So I inform my customer about this and she said she can’t afford the cost and moreover the TV is old fashioned. I was so much disappointed and felt bad I could not finish this repair work. This time “it’s the unfinished repaired work “.
This article was prepared for you by Imoudu Onwumah from Nigeria. He is 62 years old and has just 3 years experience in electronics repairs. I started career in hotel industry as a chef, but then I was doing repairs only in electrical repairs as a hobbyist. In 2018, I decided to learn about electronics which through Jestine’s electronics e-books and holding my hand, am an electronics techie today.
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Do recharge of the CRT Tube and remove the internal shorts. Replace all electrolytic caps on the board. Retouch all soldering joints from one end to the other, without leaving any points. The TV will certainly come back to its glory!
Working on old TV sets and other old defect devices is always a risk we dare to take without knowing if we do succeed! Maybe you still can fix the set with Parasuraman's tips? A bit odd that they named this old TV a DIGITAL TV?
Although I still wouldn't know how to remove internal shorts in a CRT Tube or how to recharge it. I have never done this and probably never will, since these TV sets are almost completely gone now.
do not feel discouraged my friend you did what you can to get it fixed. keep up the good work. have you tried to adjust the focus on the FBT? I am sure you already know there is a knob for brightness and one for focus. have a blessed day
In this case as per your assumption cause for this fault is FBT or CRT Base is right & guide line of Mr.Parsuraman also do help. some time testing CRT Base with multimeter seems OK but it does not fit properly or may be pins of CRT is oxidized did you try to Clean it up using Petrol??.......Peel off traces are common problem due to over heating by soldering Iron. Always use solder bridge technic for removing 8 pin IC & you have to keep good Magnifier Glass for reconfirming the trace repair work. do not use open wire for jumper some time it will mess-up the time and money you spent for fixing the device.Never give up if you tired in troubleshooting put the work on hold and start troubleshooting when you are in fresh mood may be on next day......All the best..
Mr Albert
Thanks for your comments.In my country we still have some folks who still use this crt tv,just because they can't afford cost of led tv. Techies have to help them out.One old folk ask me one day if l could help her get small led tv at about 4 us dollars.I laughed.
La limpieza de toda la zona de la etapa horizontal es importante para evitar las descargas corona ,el polvo acumulado ,contribuye a eso ,algunos flyback traen 2 potenciometros de ajuste de sub brillo y foco ,otros mas antiguos lo traen alrededor de los pines del trc, medir resistencias de alto valor alrededor de este ,descartar todo esto, antes de pensar en trc malo, si hay fugas en la superficie del flayback ,limpiar bien y aplicar adhesivo resistente a alto voltaje y temperatura ,tambien hay un barniz especial para esto ,en mi zona este era un a falla comun Reciba mi saludo respetuoso
======================
The cleaning of the entire area of the horizontal stage is important to avoid corona discharges, the accumulated dust contributes to this, some flybacks have 2 potentiometers for adjusting sub-brightness and focus, other older ones have it around the TRC pins , measure high value resistors around it, discard all this, before thinking about bad trc, if there are leaks on the flayback surface, clean well and apply high voltage and temperature resistant adhesive, there is also a special varnish for this, in my area this was a common fault Receive my respectful greeting
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Parasuraman S
April 9, 2022 at 10:51 am
Do recharge of the CRT Tube and remove the internal shorts. Replace all electrolytic caps on the board. Retouch all soldering joints from one end to the other, without leaving any points. The TV will certainly come back to its glory!
Albert van Bemmelen
April 9, 2022 at 2:35 pm
Working on old TV sets and other old defect devices is always a risk we dare to take without knowing if we do succeed! Maybe you still can fix the set with Parasuraman's tips? A bit odd that they named this old TV a DIGITAL TV?
Although I still wouldn't know how to remove internal shorts in a CRT Tube or how to recharge it. I have never done this and probably never will, since these TV sets are almost completely gone now.
Waleed Rishmawi
April 9, 2022 at 3:37 pm
do not feel discouraged my friend you did what you can to get it fixed. keep up the good work. have you tried to adjust the focus on the FBT? I am sure you already know there is a knob for brightness and one for focus. have a blessed day
Imoudu Onwumah
April 9, 2022 at 4:13 pm
Mr Parasuraman
Thanks for your advice,I do appreciate.
Yogesh Panchal
April 9, 2022 at 11:58 pm
Imoudu Onwumah,
In this case as per your assumption cause for this fault is FBT or CRT Base is right & guide line of Mr.Parsuraman also do help. some time testing CRT Base with multimeter seems OK but it does not fit properly or may be pins of CRT is oxidized did you try to Clean it up using Petrol??.......Peel off traces are common problem due to over heating by soldering Iron. Always use solder bridge technic for removing 8 pin IC & you have to keep good Magnifier Glass for reconfirming the trace repair work. do not use open wire for jumper some time it will mess-up the time and money you spent for fixing the device.Never give up if you tired in troubleshooting put the work on hold and start troubleshooting when you are in fresh mood may be on next day......All the best..
Parasuraman Subramanian
April 10, 2022 at 12:35 pm
Very good practical suggestion!
Imoudu Onwumah
April 10, 2022 at 5:35 am
Mr Albert
Thanks for your comments.In my country we still have some folks who still use this crt tv,just because they can't afford cost of led tv. Techies have to help them out.One old folk ask me one day if l could help her get small led tv at about 4 us dollars.I laughed.
Imoudu Onwumah
April 10, 2022 at 5:41 am
Mr Waleed
Thanks for your comments and encouragement.l have tried to adjust focus knob.have a nice day.
Imoudu Onwumah
April 11, 2022 at 5:35 am
Mr Yogesh
Thanks for your suggestions,I will apply them in practical.Have a nice day.
Kiptoo Cheruiyot
June 14, 2022 at 4:05 pm
How much is the repair book for Jestine Yong?
Jestine Yong
June 15, 2022 at 7:36 am
Hi Kiptoo,
You can visit this link to check on the ebook title that suits your need. In the website have the ebook price:
Jestine
ivan rivera
June 20, 2022 at 2:48 am
La limpieza de toda la zona de la etapa horizontal es importante para evitar las descargas corona ,el polvo acumulado ,contribuye a eso ,algunos flyback traen 2 potenciometros de ajuste de sub brillo y foco ,otros mas antiguos lo traen alrededor de los pines del trc, medir resistencias de alto valor alrededor de este ,descartar todo esto, antes de pensar en trc malo, si hay fugas en la superficie del flayback ,limpiar bien y aplicar adhesivo resistente a alto voltaje y temperatura ,tambien hay un barniz especial para esto ,en mi zona este era un a falla comun Reciba mi saludo respetuoso
======================
The cleaning of the entire area of the horizontal stage is important to avoid corona discharges, the accumulated dust contributes to this, some flybacks have 2 potentiometers for adjusting sub-brightness and focus, other older ones have it around the TRC pins , measure high value resistors around it, discard all this, before thinking about bad trc, if there are leaks on the flayback surface, clean well and apply high voltage and temperature resistant adhesive, there is also a special varnish for this, in my area this was a common fault Receive my respectful greeting