Troubleshooting and Repairing CRT TV

[SHIVAKUMAR K]

Dear all experts friends,
Thanks for your valuable help to others in so many problems, I have problem with crt tv That is getting ON after sometime that will OFF, If we knock the Tv then it'll getting ON. somebody can help me in this case, please ...... and a horizontal line is moving up to down and down to up while the TV is ON......

 

[Ranbeer Singh]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

See..
It's clear by your talking. it's loose connection and/or soldering problem. May be second reason is power capacitor is weak.

 

[ydtech]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

The horizontal line is a sign that the problem is somewhere in the power supply, likely on the line side. Try dusting the circuit board off, taking all necessary precautions, and examine the solder joints. Look for bulged electrolytics and charred patches on the board.

 

[retrogear]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

Remove the back cover, place the television face down with the main circuit board exposed so you can see the traces. With a magnifier, look for cracks in solder or a ***** in the board itself especially around heavy transformers or heatsinks. With the TV powered on, flex or tap gently on the board with a plastic or wooden stick (non-conductive) to see if can localize the *****. If the ***** happens to be a power connection, sometimes can turn off room lights so dark and look for a spark on the board itself. The floating line can be a break in a ground connection which will induce an AC hum in the raster.

Larry G

Hmmm - I guess put the word break in where ***** is. Must be they think I'm talking about cocaine?

 

[SHIVAKUMAR K]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

Ok I'll check the Power capacitor, cracks in solder, dust in board and any other bulged capacitors. Thanks for your valuable help. I'll come back again after checking and solve the problem ..............

 

[betwixt]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

Something else to check: Look for the large capacitor in the power supply (sorry - I've deleted the schematic files so I can't give its number) and unsolder it. The pins are often riveted to the body of the capacitor, if they are you will see a ring at the end of the pin, folded flat to the bottom of the capacitor and a soft metal (Al) rivet in the middle. Often the rivet works loose due to the repeated expansion and contraction as the TV is turned on and off. Place the capacitor on a flat surface with it's pins facing up and using a SMALL hammer and flat blade screwdriver, tap the rivet edges slightly to re-tighten it to the ring. Then solder the capacitor back in and see if it works, it is polarized so make sure you fit it the right way around!

Maybe a free repair!

Brian.

 

[SHIVAKUMAR K]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

Oh Thanks Brian Sir,
have the schematic you gave me last time. I'll Do like what you have said, Thanks for coming to help me ...... If I change the capacitor also good thing No? and one more help, how to check the electronic components, if it is fault or good ? please help me !!!!!!!!!!

 

[betwixt]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

I found the schematic in my backup files - the capacitor I think is causing the problem is C507 (100uF/400V), check if it has riveted pins as I mentioned earlier but if not, you will have to replace it. Use one with the same value and voltage rating and make sure the spacing between the pins is the same or you will not be able to solder it back in!

Generally, it is difficult to test components except for resistors. Just about everything else will give readings different according to the voltages you apply to them so you need special test equipment to be sure you are testing properly. It is also quite easy to damage some components even by connecting a DMM across their pins. In the case of C507 it is quite likely that just measuring it's value would not say it was faulty, you would need an ESR meter to confirm it was unable to charge up and discharge properly.

Brian.

 

[retrogear]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

I don't have a schematic but assume C507 Brian mentioned is the large filter capacitor on the primary side? If so, It can be checked while powered on with
a voltmeter. Assuming a 110VAC input, It should measure approximately 150V DC when powered on. But more importantly, measure the AC voltage across
the capacitor. Normally should only be approximately < 5V AC if filtering properly. If the capacitor has a ***** or whatever causing it to open, the AC across it will jump to half the 110V AC line voltage or approximately 70V AC or so. If it's a 220V AC then double the figures. The AC measurements only apply if the capacitor is on the primary side.

Larry G

 

[zsolt1]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

hi ,
the horizontal line is because vertical deflection does not work. If it starts working when you hit it , it's about a loose connection .If you also have schematic the problem is easy to solve.

the horizontal deflection is related to the power supply thru the HV transformer . Even with bad filtering the tv should work , you would see a picture that is ondulated at the left and right side.

 

[BradtheRad]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

Also in addition to the large capacitor, examine all bulky components that could loosen in case the tv was dropped in the past. Wiggle them, etc. Also any component that might respond when you slap the tv and make the tv come to life.

 

[betwixt]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

Zsolt1, this is a 'hum bar' caused by 100Hz ripple on the supply line, it isn't a vertical scan problem. As the PSU is switch mode it can only be a fault on the primary side and other than a rectifer being open circuit (very rare) it can only be high EST in the reservoir capacitor C507.

Brian.

 

[zsolt1]

Re: My crt TV is getting OFF after sometime and if we knock the TV , The TV is gettin

why shouldn't be the vertical deflection since it has horizontal line (and probably sound)? if the supply is defective nothing would work no sound no remote control . Inded at color tv's 80% percent of defects used to be the smps supply & hv trafo ...

 

[betwixt]

It isn't only a line, if it was, you would be correct in assuming the horizontal scan was working but not being deflected vertically.

The symptoms are: sometimes working normally, sometimes not working at all, sometimes there is a line travelling up or down the picture. It all points to the rectified mains AC not being stable enough and the excessive 100Hz ripple is sometimes enough to prevent the SMPS starting up at all or sometimes more than it's feedback loop can compensate for. As it seems to be a mechanical problem, the prime suspects are large components which tend to break their solder joints or in the case of a large capacitor, sometimes the tag connections on the capacitor itself. C507 is the reservoir capacitor after the bridge rectifier and also physically large and heavy so it has to be prime suspect.

Brian.

 

[zsolt1]

ohh didn't reed that , you are a good doctor hehe