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My screen goes blank when I plug in the AC power cord. Someone told me the inverter board may be bad

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Check your power suply and adapter properly waltage give and also check earthing worked properly.

Posted on Oct 14, 2008

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Blank screen


  • With the computer on, use a flash light to inspect the screen. If you can see a very faint image then either the inverter board is bad or back light. Usually its the inverter.
  • If you get nothing, plug an external monitor and toggle the display to it. If you get output then your screen is bad or possibly a loose video cable.
  • If you get nothing, power off, pull battery pull all memory out. Power on computer. If you get BIOS and a no memory error, one of your memory modules is bad.
  • Still nothing, then the motherboard is bad.

Jan 29, 2013 | Acer Veriton Z290G 185 320GB

Tip

Basic LCD Monitors troubleshooting guides


By Bud Martin
First if you can, try the monitor with other PC first to make sure it is not the PC problem.
Notes: We are dealing with high voltage that can kill you! so if you are not sure what you are doing, please have it fixed by the pro that has proper tools and safety equipment. Try to use GFI outlet and isolation transformer when work around the TV set and DO NOT DEFEAT THE GROUND PIN OF THE OUTLET/POWER CORD.

The monitor will have at least 2 circuits boards, one board will be the logic board where the video cable from PC is attached to, the second board used in most monitors today is the Power supply/backlight inverter board combinations. Some monitors will have separate power supply module and backlight inverter board.
The monitor should be connected to the running PC otherwise it will go into standby mode.
The operations of each board:

1) The Power supply board:
It takes the 120vac 60Hz and converts it to high voltage DC (around 160~170vdc filtered by the 80~150uf 250~450vdc cap) by the bridge rectifiers to be used by the switching power supply circuits that converts this DC voltage into high frequency (around 50~100 KHz) AC for driving the step down transformer. The outputs (usually 2 outputs) of the transformer will be rectified by the diodes to produce the regulated 5vdc for the logic board, and regulated 12~20vdc (12vdc is usually for screen up to 17inch, 16~24vdc for 18~24 inch screen).

The power supply circuits are always on (unless the monitor uses the power switch that actually disconnects the power from the outlet which is rarely used these days) which means that it is running 24/7 using the monitor or not, any spikes and surge will be fed into the monitor power supply.

Common problems:
Blown fuses, bad caps (leaking/bulging tops or bottom seals, please note that bad cap may look normal but it can have high ESR (Equivalent Series Resistance). The DC filter cap should be low ESR type for using in the switching power supply; general purpose electrolytic types will not last very long in switching power supply circuits. Poor solder joints, over heated components.

Testing:
Plug the monitor in but do not activate the power switch so the backlight inverter circuits will be off. Check the 5vdc and the 12~24vdc to make sure they are OK. They should be tested with the load, you can use 6V 1A (6watts) lamp for the 5vdc, and car lamps such as 1157 (12v 8watts lo/26watts high) turn signal brake lamp using high filament connection for testing the 12~18vdc (or use two 1157 in series for 19~24vdc) for the backlight inverter circuits.
If the power supplies are working, the output voltages should be steady at the rated voltages. The power supply will go into shut down if it detects too much current draw due to false in the power supply or short circuits in the backlight inverter or in the logic board.

2) The backlight inverter circuits:
It takes the 12~24vdc and converts it to high frequency AC to drive the inverter transformers CCFL (Cold Cathode Fluorescent Lamp) assemblies. The transformers will drive the CCFL by applying the start up voltage (around 1500~2000v), when the CCFL start conducting, the voltage will drop down to about 500~800v.
The inverter has detection circuits to detect open circuit if the lamp is not attached or does not fire up after the start up voltage is applied, it will go into shut down. It will also shut down if the lamps draw too much current due to ages (when lamp gets old it will draw more current).
The inverter gets two signals from the logic board, one is the backlight ON/OFF signal, the other one is the Dimming signal for the lamps.
Common problems:
Bad filter caps, resonant caps (in the inverter output circuits), blown transistors/IC, shorted or open transformer winding.
Testing:
You should have spare lamps for testing the inverter circuits.

3) Logic board:
The logic board get the signals from the VGA (ANALOG) or DVI (DIGITAL) and processes them and feed them to the LCD panel T-CON (Timing Controller) board on the back of the LCD panel.
It also sends out two signals (backlight ON/OFF and Dimming) to the inverter circuits when the monitor is on and getting the signals from the PC.
If the logic board does not get the signal from the PC, it will put monitor into standby mode.
The 5vdc feeding it is converted to 3.3v, 1.8vdc by the switching buck converters to run the processor.
The logic board also sends the 5vd or 12vdc power for the T-CON board, if the voltage is not there, you will see white/grey glowing screen only.
Not much repair you can do on the logic board unless you have the full service manual and surface mount repair station.

4) CCFL and Inverter circuits testing:
If you don not have the inverter and lamp tester boxes you may be able to do a simple test by using these steps:
If the screen flashes on for a second, you can disconnect all the lamp connectors and connect it into one of the transformer output connector and see if you will see the flash on the screen, if you do, then try it with another transformer output connector to see if it also get the flash on the screen.
Repeat the procedure with other 3 lamps. If all the lamps do flash on for seconds then more likely the lamps are OK. If lamp only flash on one of the transformer output then you will know that the problem in that transformer inverter circuits.
If none of the lamps flash at all then the problem is in the inverter circuits, power supply, or not getting the on signal from the logic board.

Bad caps
http://i.fixya.nethttp://i.fixya.nete17e9cc.jpg

Power supply/inverter board (L), Logic bd. (R)
http://i.fixya.nethttp://i.fixya.netbc19983.jpg'

Dead T-CON bd, blown fuse. Get glowing screen only.
http://i.fixya.nethttp://i.fixya.net4fbd9e1.jpg

T-CON board's fuse F101
http://i.fixya.nethttp://i.fixya.net8506e44.jpg

Inverter board surface mounted fuses, F1 and F2

http://i.fixya.nethttp://i.fixya.net1bf6596.jpg
Bad lamps (Blackened ends, burnt /poor soldering)

http://i.fixya.nethttp://i.fixya.net5c8952e.jpg

http://i.fixya.nethttp://i.fixya.net4e5e9a1.jpg

Bad LCD panel (solid vertical lines)

http://i.fixya.nethttp://i.fixya.netffe90fe.jpg

Bad LCD panel due to bad T-CON board
http://i.fixya.nethttp://i.fixya.netef48b18.jpg
Failed TV and Monitors:
http://s807.photobucket.com/albums/yy352/budm
http://en.wikipedia.org/wiki/Capacitor_plague
Make your own test lamps: http://www.badcaps.net/forum/showthread.php?t=19987

on Sep 25, 2010 | Computers & Internet

1 Answer

Desktop runs but won't boot


Normally if the hard drive is bad you will get some type of message on the screen.

If it sounds like it is running but the screen is blank, then try another monitor. Maybe the monitor is bad. Try another monitor. Borrow a monitor from a neighbor, friend, relative or co-worker and put it on the computer. If the borrowed monitor works, then your old monitor is bad. If the borrowed monitor does the same thing, then your video card is bad.

If it does not seem like it booted up all the way then try the steps below.

When you plug in the power cord is there any lights whatsoever on the laptop, where the plug goes in or on the AC Adapter of the power cord?

When you press the power button do you hear fans running, hard drive spinning, lights on the computer, hear any beeps or lights constantly blinking, hear the DvD/CD drive click and the light on the drawer of the DvD/CD turn on for a second or two? If so the laptop is trying to boot or may have booted, but the screen is not showing for some reason.

Beep tones and blinking lights tells the technicians what is going on with the laptop and why it is not booting. Most times it's a motherboard issue when you hear beeps or blinking lights continuous. Most times the problem is with the memory or Video Card. Count the Blinking Lights or Beeps and take note of their pattern (1 Long or 1 Long followed by 2 Short).

Maybe your power cord is bad if you don't get anything to happen whatsoever when you press the power button. And if that's true maybe you was operating off the battery the last time you had it on and since the power cord is bad, it was not charging the battery so the battery is drained and the power cord is bad.

Maybe you have a Static Charge Buildup. Remove the Power Cord, Then Press and Hold the power button for 30 seconds. After 30 seconds plug the power cord back in and hit the power button to see if it boots.



Maybe your memory is bad or the memory slot is bad.

Remove the Power Cord, Open the Case and remove one of the memory chips. Set the chip aside then try rebooting the computer. If it boots, then you know the memory chip you set aside is bad so mark an x on it with an ink pen. If it fails to boot then move the chip to the next memory slot and try rebooting. If it fails take the chip out and set it aside, then put the other chip in and try booting it in both slots. If it boots, just to verify that the chip set aside is bad, mark an x on it and put it into the open memory chip slot and try booting.

May 09, 2012 | HP Computers & Internet

1 Answer

Benq fp581 screen goes blank after about half a second evertime i turn on my computer.


Even thought the monitor looks blank check to see if you can see a faint image (shining a flashlight at the monitor sometimes helps). If you can see an image it could mean that the inverter board has gone bad.

I have also heard of an overheated computer causing a similar problem.

May 20, 2010 | Computers & Internet

2 Answers

Getting a black screen and no device found. what


First unplug everything from your AC/outlets.Then systematically check every plug going to and from your screen by pulling them out one by one and reattaching them. POWER cord / VGA cord .The VGA cord looks like a D and has 15 pins it goes in easy no force is necessary, thumb tight the screws on each side.Now power cord make sure it's tight, in the socket.Then plug your AC plugs back into the wall. If that doesn't solve your problem either your screen has gone bad or your video card. Good luck!

Nov 15, 2009 | Dell Dimension 3100 PC Desktop

1 Answer

Computer brightness just dissapeared randomly and brightness and contrast is at 100% can still see the screen but just barely


If you have a laptop or, flat screen monitor; as, opposed to a CRT monitor[. your screen brightness is provided by one or, two tiny fluorescent tubes commonly known as a "cold cathode" these are powered by a circuit board known as an inverter board that is like the ballast in your office fluroescent light.
Just like the ballast aforementioned:The inverter board changes the DC power of the laptop or, flatscreen monitor to an AC amplified voltage to light the display.
If your screen shows a red color or, takes time to brighten or, flashes on and off or,flickers like a bad fluorescent light in your office This is most often the problem. You can purchase replacement parts fot the cold cathode and, or; the inverter board and find instruction on how to change these components online in the manual of your respective computer or, on e-bay on such sites as; laptoppartsdirect.com

Apr 23, 2009 | Computers & Internet

1 Answer

Mi computer doesn't work anymore. It's an HP tx1220. My warranty has expired and a technician has told me that probably it was the mother board. What can I do?


Ok what do you mean by doesn’t work?
No power? no lights? dead?

Have you tried a different power cord?
I ask this because of these things

  • Laptop power cords can just give out without warning

  • And just because the green light on the power cord is lit does not mean it is putting out enough power or any at all

  • And even if you test the power cord and it reads the correct voltage does not mean it is still putting out enough amperage to handle a load (like powering up the computer) Of course that is extremely rare but I have seen that happen before

  • Before giving up hope I would try borrowing another cord from someone with an HP laptop or one of those I-GO laptop cords with the changeable tips or something or even better yet try your power cord on a different laptop and if the other laptop turns on .then well I am sorry

NOTE: if your power cord has a little green light on it and that light goes dim or starts flashing as soon as you plug it into the laptop then that is a very good indication (9 times out of 10) that your motherboard has gone bad and shorted out somewhere.

But there are too many possibilities of what could be wrong with out more info

When you plug it in do any lights on the computer come on at all?

I wouldn’t give up all hope yet .. that is a pretty nice little computer and worth trying to figure it out.

Nov 25, 2008 | HP Computers & Internet

1 Answer

I turned on my laptop after an hour i turned it off, and it started up ok, just without any picture. The screen is blank, but if I tilt it to the light, I can see everything, but just barely. it's like the...


Have you tried tilting the LCD and see if the symptom change?
If tilting the LCD shows good video, then you have a loose or bad LCD cable going to the System board.
If tilting the LCD does not change the symptoms,then it is the "Inverter" board.
The laptop have an "Inverter" board that goes out and causes this problem. It is located just below the screen on most laptops. I usually purchase them from here:

http://www.smartmicrousa.com/

You may have to copy and paste this link into your browser.

If I could be of further assistance, let me know. If this helps or solves the issue, please rate it.
Thanks, Joe
Nashville,TN

Oct 13, 2008 | Computers & Internet

1 Answer

THE SCREEN IS BLACK ON MY SCEPTRE 17" X7 MONITOR. THE GREEN LIGHT IS ON AND THE SCREEN FLASHES.


Hello JELSMA3,

This means your inverter (back light) component is bad or going bad. It needs replacing. Not sure what they go for but I was told by someone they run for about $20.00 . Once your replace the inverter, your monitor will work like new again.

Good luck.

Jul 25, 2008 | Computers & Internet

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