Retrace Line and Red Background in TV Repaired
On call from one of my friends about his TV which works intermittent. symptom he stated as audio is ok but sometimes all of sudden picture disappears and screen become red with some horizontal lines.
It was Sunday so I have made plan to visit his home as he is staying in same building.
So on visit his home and powering up the TV – I can see the same symptom as stated by him. So I have opened the TV for the fault finding
This is a china kit I have cleaned the dust with help of brush and start visual inspection on component side I did not found any suspected sign of physical damage. I have tested with help of the screwdriver handle by taping on the PCB but there is no effect on the screen (On taping you can find exact location of loose connection or dry solders on the PCB).
Then I have started inspection on CRT PCB just for reference because it was red color on full screen and this PCB having RGB amplifier section on it. So I took out the CRT Base circuit and on visual inspection I found color on the PCB Component side tuned darker near some components. So first I have decided to do some voltage test before disturbing any component. So first I have to check voltage between 135 to 180V DC on RBG Transistors Collector of all three transistors.
On PCB Component side I found these transistors marked as V902 /V912 /V922. So I tuned the PBC back side to find which transistor is belong to which color. But surprisingly I found there is no marking either on component side or solder side!
Now I have stared voltage testing. First I have tested collector of V922 I found 142V DC.
Found 174V DC on V922 & on V902 I found 10v DC
So suspecting this transistor I have removed the transistor and checked it with the multimeter, out of the circuit but it seems ok.
So on doubt may be under load this can behave differently I have interchanged the transistors as these three transistors are of the same value.
But the problem is same. So using my magnifier I have inspected the CRT PCB and found some dry solder.
With this I have checked main PCB also with magnifier look what I found
So after doing this dry solders and hair line crack repair I have turned on the TV
TV is back to the life.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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Note: You can check his previous repair articles in the link below:
https://www.electronicsrepairfaq.com/1554-ohm-in-speaker-caused-low-sound-problem-in-tv
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Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is http://www.NoahtechElectronicsTraining.com. You can check out his repair blog at http://www.JestineYong.com
25 comments on “Retrace Line and Red Background in TV Repaired”
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Good job YP
Jai,
Thanks for your feedback.
Hello!
Good job Mr. Yogesh!
Mihai.
Thanks for your feedback.
Good job, Yogesh. Bad solder joints can make you want to pull your hair out while troubleshooting! It’s the first thing I do anymore is to look for bad solder joints, unless I see something that is obvious.
Sir,
Thanks for your feedback.
You have done a good job sir
nice ob
Thankyou Mr. Doraiswamy
Excellent work’.
Thank you! Jams.
Its ALIVE ! . . . . .to show TV programs for years to come, until the picture tube gets too low in emission and gassy.
The R907-R917? and R927? power resistors associated with voltage supply of those 3 driver transistors has the one R907 associated with the
V902 driver transistor that REALLY COOKED. Cosmetically I would probably have changed out all 3 to match.
Assuredley the only reason for the survival of the R907, was for all of them being metal film units.
Edd whatley.
Thanks for your feedback.
i had planed to replace all of three resistors but in our surrounding this resisters are not available now for sale. rather they provide new KIT as per the specification as a replacement hence i decided to let it be as it is
till the life of the component.
Good job!
Thank you Sir.
sir I have a 15 year old Samsung CRT 21″ TV when I switch on the TV sound come first but picture come very late
sir what is the problem
please help
Sagar,
First of all check +B Voltage if it is good then simply check the capacitors & other components around video IF, video amplifiers, video output section.
I encounter this fault a lot and the solution is never the same. Sometimes the fault comes from the jungle ic where the RGB is faulty,it should normally be around 2,2vdc.
Peter Kwele,
Thanks for your feedback.
you are right most of time solutions is never the same .
Sir thanks for the that problem,but what causes a tv when switched on works well for some minutes and suddenly goes off but standby indicator remains on its china made 17 inche pls help?
Just look out for over heating components which my causing this symptom.
Be careful discharge the big capacitors before searching for the culprit.
thank for your kindly and more helpful ideas my friend.
dear,justine yong and dear brothers,please help me to solve my videocon ctv 21” with woofer.here the problem is my videocon tv shows the picture but the picture is very dark with full brightness with white retrace lines from top to bottom of the screen.i measured the b+ voltage but the 180v line coming from LOT is connected to crt base pin.and 3pins are hooked from the main board to crt base board.and thease pins are heater,gnd,180v line.but when measured the voltages at the LOT-side there is apin of LOT-which is alredy marked with its volage output .the 180v come from that pin and given to a diode and a resistor is connected in series with it.and a capacitor is connected across it in series.but the 180v is present at the cathode side when i removed the resistor is in series with it.when resistor is coneected the volage is dropped to near 30v.hence missing 180v to crt base is causing the blue tint with white retrace lines problem then what should i do to fix this problem.so pleae assist me to solve this problem.please
thank u sir! for ur very nice lecture!
Excellent job