I have a Dell E151FPb That won’t come on. The Power LED flashes green, but that’s all that happens. Is it worth fixing or should I just toss it?

HI Terry,

Check all filter capacitors first before throwing it away. Make sure the output voltages from the power supply are good and stable.

Jestine

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HI Roke,

Finished reading your book on the LCD Monitor Repair.  The book gave me a starting point on how to repair this LCD monitor. Applied everything I read to the subject LCD monitor.  The monitor blinks after power turn on.  This is what I did: 1.  Made voltage checks on the secondary output for the “ON” signal from the main board.  Voltage is present and stable approx  4 volts.

Noted.

2. Made voltage checks at the backlight inverter input circuits / board.  Voltage on the connectors indicate a 15v and 60v.   Both voltages are present and stable.

You mean the backlight connectors? If yes it should have about 400 to 800vac.

I did not see an inverter IC on the inverter board, except HV xfmrs and transistors.  Made cold checks to all the transistors on the inverter board.

Try see from behind the board. It should have  at least an inverter ic.

They all look good, no shorts, partial shorts or opens.  The voltage checks were done with no input signal. My question is, could I disconnect the back lights one at a time to see if the blinks will stop and HV present with partial illumination on the the  screen display?  Will disconnecting turn off the voltages that I have just checked?

You can try that but usually the high voltage will shutdown if the feedback circuit detected no load condition.

Is there a way to isolate the backlight lamps one at a time and still keep the set running, of course, with the  HV present at the connectors, if the problem is one of the backlight?  I did not make a HV check at the backlight connector. Also, do I need to connect  a signal input to make the voltage checks?

You can use a backlight tester and you can get one from ebay.com  or you can follow this article:

http://www.bestelectronicarticles.com/consumer-electronics/lcd-televisions/how-to-bypass-lcd-tv-inverter-board-shutdown-backlight-system.html

Could the main board be defective?

There is a possibility because the signal from the power LED is was coming from the MCU in the mainboard. Before that you need to connect to a signal source.

Also notice the voltages start to disappear after a few minutes of power   turn on.  I am thinking this is because there is no input signal ( Cable/Computer/Video) connected.  Is this correct?

Yes you are right. When do any troubleshooting you need to put in the signal.

Jestine

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i have a new dvd disc that i cant get the voices on the disc is fine on afriends dvd but on mine i get the back ground soundno voice audio it isturned on any other dvd is fine

HI Robin,

It could be due to the setting of your DVD player to play 5.1 surround but you
do not have a surround system. Go to your DVD’s audio setting and
change it from 5.1 to normal stereo. Hope this helps.

Jestine

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Dear Sir,

The initial problem with my intex 15″ LCD Monitor was dim display.
So replaced lamp drive IC ME4544 with 4502, now the display is OK but
the screen is flickering. External power supply, inverter & lamp are OK.
Please help me to find out the problem.

Thanks & Regards

Guru

HI Guru,

If all tested good then the panel may have fault. Try check with your analog meter at the connector of the backlight to see if the ac voltage is stable or fluctuating.

Jestine

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Hi Mr. Jestineyong,

I appreciate your urgent reply.

I attached a photo of the picture of lcd tv that im trying to repair.

Im hoping you could give me idea of resolving this trouble.

Thank you very much!

Hi Kith,

Most probably the problem is in the t-con board. Before that make sure no loose cable connection between the t-con and the mainboard. Check to see if there is any burn ICs in the t-con board. I don’t think is the service mode problem because it would not cause the color to be in that way-negative picture.

Jestine

===========================

Dear sir,

With reference to my previous fault, the smps outputs are normal (77v for eht, 6.6v for filament) when i open the booster mosfet, the monitor runs normally, but when i connect the booster mosfet, HOT becomes short immediately. I think boosting voltage is too high. How could i diagnose it. MOSFET and transistors connected with gate are ok, gate has 3v input from transistors emitter. Collector supply is 11v. When i connect 100w lamp between eht and HOT collector, i get 220v at eht supply and bub glows half of the normal light. why so high voltage is developing by booster.

HI Gopal,

It can be the gate signal problem that have boosted the B+ to become very high. It should have about 10 to 12 volt peak to peak. You may need to check components along the gate signal line.It can be an open resistor or a leaky transistor.

Jestine

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HI Salvador,

I’m mr. salvador blanco from Philippines. i have just bought your e-book (Testing Electronic Equipment, actually this is my second book which i bought from you the first one is on how to repair LCD) and i’m on my 3rd day of reading your e-book when i read the portion about the tester with output of .6 volt. My question is how will i know it if my tester has an output of .6 volt.

Thanks for the support on my ebooks. You can test it by using another voltmeter. Just the place the voltmeter probes onto the probes of the meter where you want to test the output voltage.

Another thing is i want to ask you guidance where i will start checking my LCD (which i attached here) to fix those white line which occur on both side of it.

thank you very much and more power to you and your company,

It seems to be the problem of the lcd panel but before that make sure the cable between the lcd panel and the mainboard is good.

Jestine

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Hi Justine, I’m working on a playstation that has surface mount aluminium electrolytic capacitors. Do you test them with an ESR meter or some other way? Thank you for the help.  Don

HI Don,

Yes i test them with ESR meter. If it leaks then just direct replace because sometimes it will still test good using esr meter. The leakage have not reach to a level that can be detected by the ESR meter.

Jestine

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i try light bulb method, i remove the horizontal output coil and fix bulb. result shown bulb no lighting and output voltage fluctuate. maybe primary side got problem??

Hi,

http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems

If it still blinks that check the power supply.

Jestine

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Please Suggest shall I use 1MHz Oscilloscope for testing.

HI Nanjappa,

You can try to check the output from the power ic with your scope (assuming the power supply is in good condition). If there is a waveform then it is good and if there is no waveform that means the scope can’t be used to check the waveform and you need a higher bandwidth scope.

Other than checking the waveform of the output of power ic, you can also use scope to check the dc output voltage of the power supply to see if there is any ripple or not.

Jestine

==================================

Dear Mr.Jestine,

How to check an smd inductor? that is usually mark PL0,PL1,etc..
I have try to use blue ring tester,but it’s not accurate,and it always
show shorted, while it’s not.
Try to use multimeter, not really help either.
Can you tell me how to test a shorted smd inductor?
Thanks in advance.

Best Regards,
Julianto.

HI Julianto,

A smd inductor is too small to be tested with blue ring tester. Blue ring tester is for a bigger coil. Using an ohm meter to check on the smd inductor is already good. Since smd inductor is so small thus chances it get shorted between winding is almost to none.

Jestine