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How to diagnose bad capacitors in a flat panel LCD television

I see a lot of bad capacitors in my daily grind and most of the time the symptoms are very similar, even across different brands. What I see most commonly are bad filter capacitors on power supplies. My customers will tell me that the set used start up fine then over time would take longer and longer to finally start, or they would have to press the power button several times before being able to watch tv. In these cases I remove the back panel and almost always see a bulged or burnt looking cap. A good rule of thumb when replacing caps is to keep the capacitance the same (1000uf or whatever your cap value is) and go up on the voltage at least 10 volts. Any bigger and the cap may not fit.
As always be careful when working on your own tv and make sure it is unplugged when you start the disassembly. Caps can hold a significant charge so avoid touching both pins while it is in circuit.
When in doubt, call a professional.

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bad capacitors Nichicon UHN1C821MPP

Um... capacitors aren't measured in MOhms (resistance or impedance), they're measured in uF (microfarads of capacitance).

Brand is of nearly no importance (you can use Nichicon, Rubycon, Sprague, any decent brand), but the uF rating and the voltage rating MUST match the originals - do NOT try to use an antirely different capacitor, it can destroy other parts (like rectifiers or power transformers), or burn PC traces right off the board.

Nov 05, 2013 | AOR Radio Communications

1 Answer

Shrinking horizontal screen image appears with black border approx 1/2" on both sides

The most likely cause is a dried up main filter capacitor. Once the effective capacitance drops low enough, 120 Hz (or 100 Hz in countries with 50 Hz power) ripple will make its way into the regulated DC supply (assuming full wave rectification).

Another likely cause of similar symptoms is a defective low voltage regulator allowing excessive ripple. The regulator IC could be bad or filter capacitor following the IC could be dried up.

The best approach to testing the capacitors is to clip a good capacitor of approximately the same uF rating and at least the same voltage rating across the suspect capacitor (with the power off). A capacitor meter can also be used but the capacitor may need to be removed from the circuit.

Once the capacitors have been confirmed to be good, voltage measurements on the regulator should be able to narrow down the problem to a bad IC or other component.

Feb 21, 2010 | Dell E551 15" CRT Monitor

1 Answer

it will not turn on the standby light isnt even on

The Vizio VP322 is notorious for having bad capacitors on the power supply circuit board. They will probably be bulging and may have electrolyte leaking. I replaced four bad capacitors (with a different brand just in case) and fixed it. Total cost under $10. A lot cheaper and better than replacing the whole circuit board which may contain the same "faulty" capacitors from the factory.

Nov 11, 2009 | Vizio VP322 32 in. Plasma TV

1 Answer

Have a problem w/ a Gateway FPD2275 W. When I

This is a common symptom of the backlight failing. Without the backlight, even though the display panel still works you can't see it. The backlight lamp itself is probably OK. It's the inverter circuit that provides lamp power that goes bad.

The usual cause is failure of parts called capacitors in the power supply section. It is possible to open the monitor (not always easy, but possible) and check the capacitors. Often they look bad with bulged or split tops or leakage at the bottoms. Replacing them with parts of the same capacitance rating and slightly higher voltage usually repairs the unit. I've never worked on this particular model, so I can't tell you specific parts. But there are a lot of sites with information on repairing different brands, so a search on the Web may help. There are also youtube videos for some models showing the whole procedure.

Mar 31, 2009 | Gateway FPD2275W LCD Monitor

2 Answers

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Hello jpm1lo, your problem needs someone with some repair skills to assist you, firstly your TV has both a horizontal and a vertical circuit,your problem is in the vertical circuit. The IC (integrated circuit) in the vertical area should be changed together with the 2 or 3 cylindrical capacitors ( number will vary in different brand names) also in the same circuit. This will rectify your problem.....Rudney

Mar 22, 2009 | Sanyo DS27800 27" TV

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