Olevia 242FHD-T11 no picture, but has sound

[jeepitbull]

When I first started having problems I would have to turn the TV off and on about 4 times in order to get sound. Then it started taking a few tries to turn it on. When it's in standby mode a blue light is on. As soon as you hit power the blue light will go off. It was getting to the point where I would have to unplug/replug it into the wall several times before I could even get the blue light to come back on. When it would finally come back on, I would press power and the blue light would go off but nothing else happened. I did some research and heard it could be a bad power supply. I ordered one off ebay and when I put it in the TV, it started up like it is supposed to, but now I have no picture-but I do have sound (and the "ghost" images) . I have never had any problems with my backlight inverters, but now they are not lighting up. I thought maybe the power supply wasn't working right so I exchanged it. We got the new one today and the same problem happens so I know it's not the power supply. I'm getting very frustrated and would really like some advice as to what to try next. Could it be the backlight inverters even though I've never had a problem with my picture? Should I check out the T-Con? HELP?!?!

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

Two simple questions - 1. do the backlights come on? 2. Can you see a good (if dim) image when you shine a bright light on the screen at an angle?

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

No, we don't see any backlights coming on. When we hooked it up to the cable, I could make out the writing on the top of the tv (MSNBC). The thing I don't understand is that our picture was coming in perfect, we just had a power problem. Now we have the power problem fixed and we have no picture. There aren't any bad caps on the backlight inverter boards.

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

No, we don't see any backlights coming on. When we hooked it up to the cable, I could make out the writing on the top of the tv (MSNBC). The thing I don't understand is that our picture was coming in perfect, we just had a power problem. Now we have the power problem fixed and we have no picture. There aren't any bad caps on the backlight inverter boards.

I believe Olevia used Darfon inverters - sort of the Yugo of the inverter world - but not quite that good. Check the voltages out of the replacement power supply.

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

First off, thanks for your quick reply!
We checked the voltage coming off the power supply on the blue wire going to the backlights (we read this somewhere) and it was reading 4.95. On the new power supply we got today it was also 4.95. My husband doesn't know if that's the right wire to check or not. How exactly do we test the wires to make sure we are getting the correct reading. As you can tell, we are not experts on this but we are learning fast!

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

First off, thanks for your quick reply!
We checked the voltage coming off the power supply on the blue wire going to the backlights (we read this somewhere) and it was reading 4.95. On the new power supply we got today it was also 4.95. My husband doesn't know if that's the right wire to check or not. How exactly do we test the wires to make sure we are getting the correct reading. As you can tell, we are not experts on this but we are learning fast!

I have never seen an inverter that takes only 5 volts. It's been said many times, many ways, 'A Picture is worth a thousand words.' If you attach (Using 'Manage Attachments' - below the text entry area) pictures of the top of the inverter there is an excellent chance that someone can identify the points to test.

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

Here's the picture.

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

Here's the picture.

The two pins on the left are On/Off and Brightness. 5V would make sense for the On/Off control. The red wires are inverter power - probably 24 volts, maybe only 12 volts. The black wires would be ground.

This is only half the inverter set; there is usually a slave inverter (this is the master). These are notorious for failures - especially the slave inverter.

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

This is the one on the left side (if looking at the back). So the one on the right side would be the slave inverter? If so everything on that one looks fine too (no bulging or leaking caps)

[rayrod81]

Re: Olevia 242FHD-T11 no picture, but has sound

Sounds like the main board is possibly the culprit. I had a 242-T11 that acted the same way and all the voltages coming of the power supply were good. The LEDs on the main board would light up, the blue light would go off at first power up but had no picture and then I could not power off the without unplugging the mains. Replaced the main board and the TV came back to life. The 4.95V is for the ON/OFF line on the inverters so that should be there.

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

This is the one on the left side (if looking at the back). So the one on the right side would be the slave inverter? If so everything on that one looks fine too (no bulging or leaking caps)

Let's take this in a methodical fashion. One of the common fallacies is "I replaced xxx part and it fixed my TV, so if you you replace xxx it will fix yours too." Note Rayrod's post. Does your TV respond to the remote? Can you change channels / turn the TV off, then back on?

With the TV plugged in, but off, check the voltage at both On/Off and brightness pins. Note the voltages. Now turn the TV on. Have the voltages changed? If they 'twitched' as the TV is turned on, then returned to their original values, suspect the main board. If they change and stay at the new voltages, suspect the inverter.

The common failure mode of the slave inverter does not involve bulging caps. Instead, the driver transistors short. The controller IC is also damaged. A picture of the slave inverter would help.

Prices range from $40 to $120 for a pair of inverters on eBay.

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

With the power on, the on/off on the master goes up to 4.95 and stays there. The brightness on the master goes up to 3.30 for about 5 seconds and then drops and stays at 1.88. The power stays at 24.0.

On the slave inverter, the on/off stays at 4.95, the brightness stays at 1.88, and the power stays at 24.0.

The remote works to turn the TV on and off but I can't say whether it changes channels since I have no picture.

Does that mean it could be the slave inverter since the values stay?

Once again, thank you SO much for all your help!

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

With the power on, the on/off on the master goes up to 4.95 and stays there. The brightness on the master goes up to 3.30 for about 5 seconds and then drops and stays at 1.88. The power stays at 24.0.

On the slave inverter, the on/off stays at 4.95, the brightness stays at 1.88, and the power stays at 24.0.

The remote works to turn the TV on and off but I can't say whether it changes channels since I have no picture.

The technique some of us use is to hook up a signal source - my favorite is a Nintendo - and step through the inputs listening for the audio. The opening theme from the 'Lion King' game is engraved in my memory.

Does that mean it could be the slave inverter since the values stay?

Not necessarily. I've marked up a couple of picture and attached them.
The red circle is a fuse. If open, there is definitely a problem on the card.
I'm assuming these are similar to inverters from LG Display. Look for damage on the IC in the area circled in yellow.
The transistors are circled in blue, I've numbered the pins on one of them. Check for shorts 1-2, 1-3, 2-3 on all of them.

Once again, thank you SO much for all your help!

Pay it forward.

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

Thank you for the diagram. To me, the fuses don't appear to have any damage. Is there a way to test them? There doesn't appear to be any damage on the IC. This is our first time dealing with anything like this so could you please tell me how to check for shorts on the transistors?

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

Thank you for the diagram. To me, the fuses don't appear to have any damage. Is there a way to test them? There doesn't appear to be any damage on the IC. This is our first time dealing with anything like this so could you please tell me how to check for shorts on the transistors?

Testing fuses is easy. Set your DMM to the 200 Ohms range, then touch the probes together. That is the resistance of the leads. If your leads are good the resistance will be below 1 ohm. Remember the reading.

Now touch each probe to one end of the fuse and note the reading. Subtract the resistance of the leads to find the resistance of the fuse. A good fuse will have a resistance of less than 1 ohm.

The transistors are even easier - no arithmetic is required. Note that I have numbered the legs 1 & 2, and the tab 3 (the stub middle leg is connected to the tab). Place one probe on leg 1. Place the other on leg 2. A good transistor should have a reading of over 100 ohms. Now measure the resistance from leg 1 to the tab. And from the tab to leg 2. Each of these readings should also be over 200 ohms. Now test the other three transistors. Then test the fuse and transistors on the other board.

If you find a problem on either board, you have a dilemma. One board tested good, but it is just as old as the board that failed. Do you replace only the one that failed, or both?

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

We set it to 200 Ohms, and when we tested the transistors we didn't get a reading. We then switched it to 200k Ohms and we got a reading of 8.3 on each transistor. What does that mean? The fuses tested fine.

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

We set it to 200 Ohms, and when we tested the transistors we didn't get a reading. We then switched it to 200k Ohms and we got a reading of 8.3 on each transistor. What does that mean? The fuses tested fine.

That means the transistors are probably fine. The usual failure mode of these FETs is to short. My conclusion is the inverters are probably not the cause of the problem.

PlainBill

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

Reviewing the history of this TV, the original problem sounds like the classic symptoms for bad capacitors in the power supply. I'm not sure what to make of the current problem, except possibly a problem with the power for the inverters.

Oops!! I just had a thought. Try a simple test. Turn the TV on in a completely dark room. See if there is a brief flash from the backlights as teh TV comes on.

PlainBill

[jeepitbull]

Re: Olevia 242FHD-T11 no picture, but has sound

I have a brand new power supply so it's not that. I'm confused though-I thought the transisters should be over 100 ohms but ours was reading 8.3 (on the 200k ohms setting).

The power to the inverters is good and there is absolutely no flashes from the backlights.

Could it be the main board?

[PlainBill]

Re: Olevia 242FHD-T11 no picture, but has sound

I have a brand new power supply so it's not that. I'm confused though-I thought the transisters should be over 100 ohms but ours was reading 8.3 (on the 200k ohms setting).

The power to the inverters is good and there is absolutely no flashes from the backlights.

Could it be the main board?

A reading of 8.3 on the 200K ohm setting means the transistors show a resistance of 8300 ohms. I consider that perfectly reasonable for an in-circuit measurement of a good transistor. Usually failures are catastrophic, resulting in one or more shorted transistors. If they were shorted I would expect a reading of under 5 ohms.

I do not understand what is happening on this TV. By the voltages, the backlights should be on. Your visual and electrical examination shows no inverter problem.

There is a failure mode where the inverter controller detects a fault and shuts down the backlights. Normally this takes about 2 seconds, so the symptom is called 'two seconds to black'. I struggled with a TV that had a 'black screen' problem for many hours before I realized that the backlights were on for much less than a second. The fact that I was working in a well lit area did not help. Only after Wizard gave me a (verbal) kick in the pants did I realize I was looking at an inverter problem, not the control problem I had been pursuing.

That is the reason I suggested trying the tv in a dark room. Under those conditions you should be able to see even a very brief flash.

The other thing to try would be going back to the original power supply and seeing if the backlights work. Double check the seating of all connectors.

PlainBill