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Repair 74cm TV Power Supply

Smoothing Capacitor does not discharge and TV is dead. I measure 312DC Voltage across it even when Set is OFF.

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Hi there, check the bleder resistor, it was 100 kilo ohms or up, near the biggest capacitor at the power supply. do some test and check up. ty

Posted on Feb 16, 2008

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Tv is dark with a horizental white gong thru the middle


Check the smoothing capacitor connected to the +B voltage line, at the main power supply output voltage. It will be an electrolytic capacitor, usually come to a capacitance value between 100MFD 160VDC to 220MFD 160VDC. You're seeing the supply HUM by the screen. Products powered by electricity should be serviced or repaired only by experienced professional technicians. Any attempt to service or repair the product by anyone else could result in serious injury or death. If you are not familiar with electronics, do not attempt to repair.Whether you suffer fatal electrical shock.Instead, contact the nearest service centre. To get some details, http://electronicshelponline.blogspot.com/Pull up older posts.

Dec 04, 2013 | Toshiba 36A10 36" TV

1 Answer

Lines and distortion across screen


Check and replace the smoothing capacitor used at it video output voltage This capacitor can be located at the neck board of picture tube.To get more details, http://electronicshelponline.blogspot.com/ Pull up older posts.

Nov 29, 2013 | Philips Magnavox 20MT133S 20" TV

1 Answer

Too much Brightness


Check its video output supply voltage. If it is less than normal, this kind or fault can occur. Check the smoothing capacitor used there to smooth this voltage. Replace it. These components can be located at the video output card, which is plugged directly to the back of the picture tube.

Nov 11, 2013 | LG 30FS1D TV

1 Answer

Vertical lines on screen


Check the smoothing capacitor for the main secondary power supply voltage. If you wish to get more details, check this site. Pull up older posts there. Check the site with patience, as it has over 2250 posts now. All are related to electronic equipment repair help.

Apr 09, 2013 | Samsung Standard (CRT) Televisions

1 Answer

I have horizontal lines over the whole tv,but the tv play you can see them good on some channels.Wat could be the problem?


There is mainly two reasons for this fault. The smoothing capacitor to video output supply voltage be bad, or the screen voltage to CRT is more than normal. These lines [thin horizontal lines runs across the screen; an inch apart or so to entire screen] is technically called 'vertical retrace lines' If you wish to get more details about this fault, check this site. It has details about it. Pull up older posts there.

Feb 10, 2013 | Standard (CRT) Televisions

1 Answer

Sylvania tv shrinks the sides


Check its secondary power supply voltage from SMPS power supply. Check the smoothing capacitor connected to secondary power supply voltage, replace it.

Jun 13, 2012 | Sylvania 6420FB 20" TV

1 Answer

The picture does not come on when I turn it on.


Hello

Your TV is now in dead condition I should say. You should strart from its power supply regulation section itsef to rectify the fault. Look into the fuse, a glass fuse is there, in power supply board. If It has found blown, make sure that there is something short in either power supply regulator side, of on the other part of the printed circuit board.
You just place a fuse of same rating as used, if the fuse is blown. If the fule you installed newly also blows off, check first the retifier stalk for any leak. The stalk contains four diodes, even any one of them gets shorte, fule will blow up. If there is no leak in the retifier stalk, measure the voltage resistance across the main filter capacitor, a bulky one capacitor fitted in the power regulator section. If you see a full deflection on meter, it means that there is some dead short inside the power regualtor system.
Usually Sony uses STR regulated type power supplies, and some uses MOSFET [Metal Oxide Semiconductor Field Effect Transistors], as switching elements. Bothe of these types can be shorted, due to a high voltage spikes, or a sudden supply failure and restart.
Check out short test on these components, out of board, that is, desolder it out from the circuit board. You just resolder one by one and measure the resistance ad described above. Thus you can find out the exact component, that have a short. If any of these components shorted, check the entire power regulator section for any more component failure, like zener diode short, resistors opened, and so on. You should have a concept of soldering and a little knoledge in electronics. There will be a MOV [Metal Oxide Varistor] fitted across the power supply input, which look like a disc capacitor. it will get shorted when a certain voltage spike occures abvve its rated voltage, and apply a dead short at the supply stage. If any of them used, desolder it out and check for any leak, and is found leaky, replace it. It is used as a saftey measure, and without it the set will work fine.
Just check these and if you find any difficulty, contact me through Fixya. Ok.

Nov 29, 2010 | Sony KV-36XBR450 36" TV

1 Answer

Several lines run across the top of the screen


Several lines acroos the screen at the top along with picture is a typical fault. You are seeing vertical retrace lines. Either the supply smoothing capacitor to the power supply given to vertical output Ic or vertical output capacitor connected to the vertical output pin of that Ic may faulty. Usually the supply smoothing capacitor seen faulty. It may be over 1500Mfd eletrolytic capacitor used there. It may get value reduced by 40 percent or so, this falult will occur. Please replace the two capacitors together and will get the result.

Oct 15, 2010 | Toshiba 27A34 27" TV

1 Answer

JVC AV-36D502: Input #3 doesn't work


Good day sir, its a different issue, about the capacitor, for as long as your replacement part is correct, it will work, now, there are several things you should check, the I/O device that controls the inputs of the TV, usually an IC, check your schematic diagram to trace the fault. check also the line from the input 3 to the controller IC on your diagram. Measure the voltage across the IC Vcc to ground if the IC is getting the right power, Low voltage can be cause by faulty capacitors, on the power supply line, or the IC itself is faulty, Circuit analysis and voltage measurements are needed to trace the faulty part. hope this helps thanks.

Oct 23, 2009 | JVC AV-36D502 36" TV

1 Answer

TV Will not fire up.


try this,hang the collector pin of the HOT then try to switch on check the voltage its 115v dc,and check also the oscillation drive at the base of HOT take your VOM at 10v ac,ther must be a flactuate at the pointer.if the two procedure are good.plyback is deffective.but if u dont have any measured voltage at the collector of HOT ur problem is in the power supply. mc44608 is use at all old model philips tv.email me for wat happend

Dec 03, 2007 | SansuiM1315 TV

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