Samsung Syncmaster 245BW

[bermudahonk]

Re: Samsung Syncmaster 245BW

Hi,
I was checking the path to pin 11, since I get there 4,62V and others get around 1V. I was using the schematics from zeha and my readings on QM803 didn't make any sense. So I cleand the surface of that item and could clearly read "3Ls". There was a fourth sign, but I could not recognize it. Still I looked the part up and as I guessed it should be some sort of an pnp thingy. I found out its a pnp double transistor. I drew it on paper and guessed my readings before making them. They turned out to be exact. I found the datasheet. Well, maby someone can make something out of that.

I still looking for the reason my voltage on pin 11 differs that much.

[bermudahonk]

Re: Samsung Syncmaster 245BW

Hi,
I checked everything ... well besides the SMD-caps but everything seems to be OK on that board of mine. The only thing that remains ist the F9222L. I will order one today. But since I will have to wait a few days until it's arrival, I'm still up for testing .

[DiyAlan]

Re: Samsung Syncmaster 245BW

Hello guys,
After 18 months, my refurbished Syncmaster 245BW has died. Last month it would occasionally make a noise that was a single, fairly loud crack. This would repeat every once in a while, but hours apart. It had no apparent effect on the display. Then last week I started to notice a flickering in the intensity of the display. The flickering was in a pattern of wide horizontal bands several inches wide, which looked like it could be the back lights. The flickering was quite intermittent, but finally the screen simply went dark. I found several comments on the badcaps.net forums that encouraged me to take the display apart and look for bulged capacitors. I did not see any evidence of bulged tops on the caps and saw no evidence of leakage. With the power supply removed from the display I applied power and measured no voltage at the 24V or 5.3V output connectors. I verified that the power switch worked and the fuses were good. I flipped the power supply board over and found two points on the circuit board that were labeled “DC 380V”. These are the leads to a large (1.2” diameter, 0.7” tall) 82 uF bulk capacitor. When I measured across these two points my Fluke multimeter read 160 Vdc. Readings between these two points and ground were +55 Vdc and -55 Vdc. It was a great display, so I would really like to fix it.

Does the power supply need to be hooked up to the rest of the circuitry in the display for the 24V or 5.3V outputs to come on?

If the 82 uF bulk capacitor was good, would it read as low as 160V with no load attached?

Thanks in advance for any insights you may be able to send my way.
DiyAlan

[jetadm123]

Re: Samsung Syncmaster 245BW

Hello guys,
After 18 months, my refurbished Syncmaster 245BW has died. Last month it would occasionally make a noise that was a single, fairly loud crack. This would repeat every once in a while, but hours apart. It had no apparent effect on the display. Then last week I started to notice a flickering in the intensity of the display. The flickering was in a pattern of wide horizontal bands several inches wide, which looked like it could be the back lights. The flickering was quite intermittent, but finally the screen simply went dark. I found several comments on the badcaps.net forums that encouraged me to take the display apart and look for bulged capacitors. I did not see any evidence of bulged tops on the caps and saw no evidence of leakage. With the power supply removed from the display I applied power and measured no voltage at the 24V or 5.3V output connectors. I verified that the power switch worked and the fuses were good. I flipped the power supply board over and found two points on the circuit board that were labeled “DC 380V”. These are the leads to a large (1.2” diameter, 0.7” tall) 82 uF bulk capacitor. When I measured across these two points my Fluke multimeter read 160 Vdc. Readings between these two points and ground were +55 Vdc and -55 Vdc. It was a great display, so I would really like to fix it.

Does the power supply need to be hooked up to the rest of the circuitry in the display for the 24V or 5.3V outputs to come on?

If the 82 uF bulk capacitor was good, would it read as low as 160V with no load attached?

Thanks in advance for any insights you may be able to send my way.
DiyAlan

If you're in the USA, the voltage across the 82uf cap will read between 160-165VDC.

Some power supplies require that everything be connected before they will start up. Try this and measure again for the 5V & 24V.

What is the part number of device circled in yellow?

[DiyAlan]

Re: Samsung Syncmaster 245BW

jetadm123,
Thanks for your reply. I am in the United States so I am applying 120Vac to the power supply.
It is a bit difficult to plug all the circuits into the power supply and still be able to access it to make measurements, so I assumed that the inputs to the supply were more important than the 6 outputs to the back lights and only connected the inputs. I turned the power on and measured 24.4V and 5.4V on the power supply outputs. I also measured the 82uF cap again and now it read 390V. Attached are some pictures of the component you circled in yellow. I think the number on the component is 4863G G0814. In one of the pictures this component looks a bit CRISPY. With 24.4 V and 5.4 V on the outputs, I measured the voltages on the 8 pins of the component with respect to the ground buss on the input power side of the board. Voltages starting with the lower left pin in the picture and proceeding counter clockwise were -56v, -53v, -55v, -56v, -53v, -50v, -40v. Doesn't sound good.
Several minutes later I measured the 24v and 5v outputs they both measured less than a volt. At that time I also measured the 82uF cap and it measured 160v.
After several more minutes and a POR the 24.4v and 5.4v outputs were back and the 82 uF cap measured 390v again.
Does this shed some light on the problem?

If I need to replace the 4863G G0814, I will need a soldering iron with a small tip as well as a solder sucker.

Regards,
DiyAlan

[retiredcaps]

Re: Samsung Syncmaster 245BW

I think the number on the component is 4863G G0814.

Voltages starting with the lower left pin in the picture and proceeding counter clockwise were -56v, -53v, -55v, -56v, -53v, -50v, -40v. Doesn't sound good.

Datasheet is at

http://pdf1.alldatasheet.com/datashe.../TDA4863G.html

For the negative voltage readings, try using the negative lead on the main filter cap for ground. That should give you positive voltage readings.

[PlainBill]

Re: Samsung Syncmaster 245BW

Guys, there is a 'gotcha' hidden in this power supply. Given some of the readings, this power supply has a PFC correction 'front end'. It also has standby and main outputs. 160 volts across the 82uF cap is an acceptable reading with the main supply off, and 380 is the design voltage with the main supply on.

PlainBill

[jetadm123]

Re: Samsung Syncmaster 245BW

Not sure what ground you're using to take voltage readings. If you measured across the pos and neg leads of the 82uf cap you should read approx 160-165VDC. Is this how your meter leads are connected when you read the 390V? Like retiredcaps says, you can use the neg lead of the cap to take voltage readings on the high voltage side. However, DO NOT use the neg lead of this cap to take voltage readings on the low voltage side!

Disregard what I wrote! I didn't see PlainBill's explanation above. Thanks!

[retiredcaps]

Re: Samsung Syncmaster 245BW

The flickering was quite intermittent, but finally the screen simply went dark.

Let's get some more basic info in addition to all the voltage measurements.

1) Does the power LED come on and stay lit?

2) If you hookup the LCD to a computer, can you see the display by shining a flashlight on it?

[DiyAlan]

Re: Samsung Syncmaster 245BW

Thanks for the the data sheet info. I used it to make some better measurements. These measurements are with respect to pin 6 which is grounded.
Pin 1 Vsense 2.49 v
Pin 2 AVout 2.60 v
Pin 3 Multin 0.81 v
Pin 4 Isense 0.013 v
Pin 5 Detin 1.89 v
Pin 6 Ground
Pin 7 Gtdrv 5.35 v
Pin 8 Vcc 15.09 v

When making these measurements, the 82 uF cap was at 390 v and the ouput voltages were present at 24.4 v and 5.4 v.

Does that make more sense?

Regards, DiyAlan

[PlainBill]

Re: Samsung Syncmaster 245BW

Thanks for the the data sheet info. I used it to make some better measurements. These measurements are with respect to pin 6 which is grounded.
Pin 1 Vsense 2.49 v
Pin 2 AVout 2.60 v
Pin 3 Multin 0.81 v
Pin 4 Isense 0.013 v
Pin 5 Detin 1.89 v
Pin 6 Ground
Pin 7 Gtdrv 5.35 v
Pin 8 Vcc 15.09 v

When making these measurements, the 82 uF cap was at 390 v and the ouput voltages were present at 24.4 v and 5.4 v.

Does that make more sense?

Regards, DiyAlan

That means the power supply is working. Given the symptoms, you should be looking at the inverter. This is one reason I often ask for an over-all picture of the entire back of the monitor.

PlainBill

[jetadm123]

Re: Samsung Syncmaster 245BW

Thanks for the the data sheet info. I used it to make some better measurements. These measurements are with respect to pin 6 which is grounded.

When making these measurements, the 82 uF cap was at 390 v and the ouput voltages were present at 24.4 v and 5.4 v.

Does that make more sense?

Regards, DiyAlan

Earilier, you said that the 5V and 24V would drop to <1V after a few minutes. Is the output voltage still going off/on, or is it now steady output?

Please post a photo of the inverter assembly.

[DiyAlan]

Re: Samsung Syncmaster 245BW

Here are some pictures of the inverter when I took the display apart. At the time I noticed that the leads going to the top and bottom lamps were not positioned the same as the rest of the leads. I just put it back together with the lamps plugged in to the inverter. This time I moved the leads of the top and bottom lamps to be in positions that are more like the rest of the leads. The display is face down since I have not put the back of the case on, but it looks like all six lamps are on steady. It would be GREAT if that was all it took to fix the display !!!!!! ;-). From the front it looks mostly dark since there is no video signal driving the display. Is there a way to make the display go white without a video signal?
Are there any other things I should do to test it? Should I let it run for a while?

Thanks,
DiyAlan

[bermudahonk]

Re: Samsung Syncmaster 245BW

Is there a way to make the display go white without a video signal?

Yes, just disconnect the plug between panel and the logic card.

[jetadm123]

Re: Samsung Syncmaster 245BW

Here are some pictures of the inverter when I took the display apart. At the time I noticed that the leads going to the top and bottom lamps were not positioned the same as the rest of the leads. I just put it back together with the lamps plugged in to the inverter. This time I moved the leads of the top and bottom lamps to be in positions that are more like the rest of the leads. The display is face down since I have not put the back of the case on, but it looks like all six lamps are on steady. It would be GREAT if that was all it took to fix the display !!!!!! ;-). From the front it looks mostly dark since there is no video signal driving the display. Is there a way to make the display go white without a video signal?
Are there any other things I should do to test it? Should I let it run for a while?

Thanks,
DiyAlan

Not sure what you did, but without a video input signal, the monitor should go into standby mode and turn off the lamps. Also, why do you want the display to go white?

[bermudahonk]

Re: Samsung Syncmaster 245BW

Not sure what you did, but without a video input signal, the monitor should go into standby mode and turn off the lamps. Also, why do you want the display to go white?

It does not. The monitor stays on and shows the "no cable connected" screen. The idea with the white screen is to see if the lamps are on, while the monitor is laying face down. That way when you lift it a little bit, you'll see the reflections much easier.

[jhead]

Re: Samsung Syncmaster 245BW

I also have this same monitor which I bought new about three and a half years ago so it's out of warranty and it faded to black just the other night I just finished taking the back panel off was suprised how easy it was to get at everything.It sounds like my problem mirrors DiyAlan's did all the visual's and everything looks to be fine.It's appearing whatever the fix on DiyAlan's monitor might also be my fix just printed out the P\S schmatic and the readings that DiyAlan got off his P\S with reply back from PlainBill that his Voltage readings look good! so I'm off to take those measurement 's will return with results.

[allenc]

Re: Samsung Syncmaster 245BW

I too have a broken syncmaster 245bw. Symptoms; no picture, blue power LED lit solid when a signal is present and flashes otherwise, host detects EDID from display.

More than enough info in this thread to begin troubleshooting. I'll post what I find.

[allenc]

Re: Samsung Syncmaster 245BW

Last month it would occasionally make a noise that was a single, fairly loud crack. This would repeat every once in a while, but hours apart. It had no apparent effect on the display.

I've heard that as well. I have two of these 245BW displays (one broken) and that loud crack happens occasionally with one of them (the one that works, incidentally.) The loud crack is probably caused by expansion/contraction of mechanical components as the display radiates heat. It does not appear to be related to the electronics; if any of the small electrical components ever made a noise that loud it would mean catastrophic failure and would never repeat.

[llotech]

Re: Samsung Syncmaster 245BW

Ok, problem is solved with replacing burned resistor RB805
Thanx cloepula for resistor

Thanks guys you are all great and definitely know your stuff!

It took me three reads of the entire thread for me to start to grasp what I was doing. I still don't know what half of what you said really means. Thanks to everyone for your help you saved me a few hundred bucks.