How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

[mlitvin]

Hi

When I connect the monitor to the AC outlet, I can't see anything change - no led turns on and the screen doesn't react. There is only some kind of a very silent click.
I've checked the capacitors on the power board, to the eye they seemed ok - no leaks, no bumps, all flat.

What should I do next?

I've been thinking to order one of these. Is it a good idea, or might I be wasting money?

Thanks!

[Rtech]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Then you need to check basic things like fuses,measure some voltages etc etc.You also need to add photos,of both sides of the boards,using 'go advanced' below, then 'manage attachments'

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

I've attached selected photos, additional close-ups are available here.

Can you elaborate on how I check the basic components?

[Rtech]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

You Need a meter ??? measure the resistance of F101,located immediately behind the AC Mains socket a Red One....then F301 a Green fuse to the left of the big capacitor.The resistance meter should be on the lowest range,and you are looking for approx the same reading as if you just touch the Meter probes together.

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

F101 should have near-zero resistance too?

Edit: of course, it's a fuse... What does the "T3.15AL" written next to it mean?

[mariushm]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Time delay 3.15 amps

Take out the power supply and the display board from the monitor (disconnect the display board from the monitor by that white strip).

Put both on a few sheets of paper to insulate them from the desk, connect the power supply and display board together by those black wires and also plug the smaller cable into the power supply (cable which goes to the "buttons" on your monitor).

Carefully plug the cable into the power supply board (don't touch any metal part with your hands now, you have high voltage on that board).
For safety, take out the cable from the mains socket, plug the cable into the power board, then plug the cable into the mains socket.

Put the multimeter on voltage DC (if not autoranging set to highest voltage) and put the probes on the large capacitor.

You should see about 350v on that capacitor. If you don't see any voltage, the fuse is probably bad, or the bridge rectifier before it is gone. If you see less than your mains voltage the bridge rectifier may be partially bad.

If everything's Ok so far, unplug the cable (pull out from mains socket) and wait a few seconds for the large capacitor to discharge a bit, then if you want also unplug the connector from the mains socket on the power supply.
Flip the power board to get access to the bottom. Now look at the corner where that connector with 12 wires is and you should see a "legend" that says what each of those wires is supposed to be:



You can see that 12 written which tells you the pin at the top is pin1 and the last one is pin 12. If this wasn't written on the board, you could also tell by looking a bit to the left: you see there a C108 and you have the + side going to pin 2 (or maybe pin 1 and pin 2) and the - (ground) goes to pin 3 and 4. So you see in the legend that the third and fourth wires are ground.

So you can see there that

pin 2 is 12v (or some other voltage > 10v, I can't tell from picture),
pin 3&4 are ground,
pin 5&6 are 5.1v,
pin 7 is backlight brightness,
pin 8 is backlight on/off
pin 9 is 3.3v
pin 10 is probably the power on led (there should be 5v or 3.3v on it when monitor runs, probably)
pin 11 and 12 are the wires through which the display board receives button presses. Depending on design, these should show 3.3v or 5v and go to some voltage between 0 and that normal voltage when pressed.

You're interested in measuring the voltages, the most important ones are 5.1 v and 3.3v - if one of those is off by more than let's say 5-10%, the display board can't start working and may not even detect you pressing the power button

Now, put your multimeter on dc voltage again, if not autoranging put it on a lower scale, let's say 100v

Carefully plug the monitor back in the mains socket and put the black probe on Ground, any one of those pins, 3 or 4.
Put the red probe on pin 2 , then on pin 5 or 6 then on 9.

You should have at least 4.95v and at least 3.2v and the other voltage on pin 2 should be within 10%.
If you don't measure anything, keep the probes on a voltage with one hand, and hit the power on button with other hand. See if that changes.

Come back when you do these and let us know what you measured.

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

I'm still alive if someone worried just took me some time to find that multimeter

So I've measured these with the display board and buttons connected:
*Digital pins:* (same on the power supply and the display board)
5.1v-GND = 5.27v (all combinations)
3.3v-GND = 3.3v
13v-GND = 13.61v
LED-GND = 0v
LED-5.1v = -2.94v
LED-3.3v = -1.05v
KEY1/KEY2v-GND = nearly 0v
KEY1/KEY2v-5.1v = 5.17v in average (about 0.1v difference between KEY1 and KEY2)
ONOFF-GND = 0v
ONOFF-5.1V = -5.21v


*Analog components:*
F101 = short
F301 = short

Large capacitor 350v = 317v


At this point I've disconnected the display board and buttons and measured these:
C118 5v 3.3uF = 3.87v
C119 10v 330uF = 5.27v
C108 25v 520uF = 13.21v
C113 16v 1000uF = 5.26v
C116 16v 1000uF = 5.27v
C112 25v 820uF = 13.20v
C107 = 11.17v
C114 = 0.053v
C301 25v 820uF = 13.21v
C302 25v 820uF = 13.21v

I couldn't read the voltage and capacitance of C107 and C114 as there was foam over the letters.

So, doctors, what do you say?

[Rtech]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Without a schematic it is difficult to understand why there is the voltage shown on C114.also why you have a minus voltage -5.21 volts measured on the ONOFF, which I assume is the backlight On Off, please confirm.

[mariushm]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Wonder why I didn't bother to search for the datasheet before?

Here it is : http://savedonthe.net/a/samsung_t200...tw20_22_sm.rar (it's going to be up for a few days)

Study the archive, lots of info, troubleshooting steps etc etc ...

The voltages look fine to me at a brief look.

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Amazing. At first glance it looks like Chinese to me, but I'll try to delve in the docs before bugging you guys further.

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

So I followed the troubleshooting manual, and noticed that it says "When turning on the Power button...". So appears that there's a power button. It's an invisible touch button on the front panel, and I found it with help of this post.

Yes I was stupid, let's move on ok?

So now I probably got to the real problem. When connecting a PC, the screen remains black. When hitting the menu button, the screen turns completely white. And the LED blinks for a few seconds.

I tried to follow the instructions on the troubleshooting manual, but they require equipment that I probably don't have (like measuring oscillation). It looks like all paths there lead to the same conclusion of replacing the display board. So maybe that's just what I need to do?

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Anyone?

[Rtech]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Or the Logic board, as you have not eliminated that.I would make sure that the problem is NOT the Power supply or Backlights,by plugging the Power Board into the mains,and plug in the Backlights, NO OTHER BOARDS or Cables.Put a 1KΩ resistor between the 5.1 volts on the connector and the Backlight on off pin,the lamps should light and stay on.If that works, then you need to put the PC together and ensure that with the PC signal applied,you get a voltage on the Backlight on off pin, which should turn the lamps on,if you do not get that, then you are looking probably at a logic board fault..but lets not get to far ahead until you do the above.

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

When you say "plug in the backlights" do you mean the little white connector that goes to the control keys?
And backlight on/off pin is the ONOFF pin on the connector that goes to the display board?

[Rtech]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

No I mean the Screen lamp connectors CN 301,302,303,and304,NOT the other one that goes to the screen connector at the top from the logic board.

[Davi.p]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Reconnect the 3 boards as mariushm said, what do you get at the pin 3,3v of the connector to the key board? What to Key1/2 if you press a key?

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

So I received a replacement display driver board from aliexpress, plugged it in, and now the display works!
Only it flickers - pretty rapidly and tiresome to the eyes.
Anything to do about this?

[Pauldesign]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

Flickering is as a result of the back lights trying to switch ON -- similar to your normal fluorescent lamp. The voltage across each in a pair might be different, which could be as a result of your PSU or the back lights could be weak.

If you take the back lights out or have spares, you'll notice what i mean, as you'll immediately see the difference in brightness intensity of the each tubes in a pair and if you measure the DC voltage across each, they'll surely be different.

From my experience and depending on the supply to the inverter (sometimes 12V), ~3V should be across each of the 4 back light connectors.

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

What can I do about it?

[mlitvin]

Re: How to troubleshoot a Samsung Syncmaster T220 that doesn't power up?

I changed the whole PSU, and it still flickers.
I understand that my next steps would be to change the CCFL inverter and the CCFLs themselves.
How do I locate these parts inside the LCD?

I found these items on eBay:
"New High-quality Notebook 22" Widescreen LCD CCFL Backlight Lamp Tube"
"1pc 4Lamp Backlight Universal Laptop LCD CCFL Voltage Inverter 10-30V For 15-26" "
They cost very little so I wouldn't mind trying them out. Would they fit or I should get specific parts for my LCD?