Samsung 215tw display cuts out

[almoodie]

Samsung 215tw.
When I turn the monitor on the video displays for a couple of seconds, then the screen goes blank. Power light glows continuously.
I opened it up. There are no bulging caps, but I replaced them all with the exception of the large 180 microF 450V.
Reconnected everything and turned it on again but problem remains.
No burned or charred components, and I can't see any bad solder joints.
Images of the power/inverter board are attached.
What should I do now?

[Razzy]

Re: Samsung 215tw display cuts out

Can you barely see the image on the monitor? Could be inverter issue.

[PlainBill]

Re: Samsung 215tw display cuts out

Samsung 215tw.
When I turn the monitor on the video displays for a couple of seconds, then the screen goes blank. Power light glows continuously.
I opened it up. There are no bulging caps, but I replaced them all with the exception of the large 180 microF 450V.
Reconnected everything and turned it on again but problem remains.
No burned or charred components, and I can't see any bad solder joints.
Images of the power/inverter board are attached.
What should I do now?

Razzy is probably right, it's most likely an inverter / backlight issue. Try hooking it up to a working computer, then shining a bright light on the screen while viewing it from an angle. If you can see the desktop or whatever the computer is displaying, that confirms it.

There are several approaches to troubleshooting this problem, all with varying degrees of risk and chances of success.

The safest is to measure the resistance of the primaries and secondaries of the transformers. I would GUESS that the primaries will be under 10 ohms, the secondaries about 1K, but there is a LOT of guessing involved in that. With luck you can work from the top of the board, the output pins (labeled O1-O6) are covered with insulation. Do this with power off, of course.

A second approach is to hook everything together in some manner that you can access the bottom of the board while it is hooked to the monitor. While the monitor is displaying an image and the backlights are on, measure the ACvoltage from the returns lines (labeled R1 - R6) to ground (labeled GND).

A third approach requires the same approach as the second, but measure the AC voltage at points V1 - V6 to ground while the backlights are on.

In all three cases we are looking for a reading that is different from the rest.

Good pictures, by the way.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

[QUOTE=PlainBill]Razzy is probably right, it's most likely an inverter / backlight issue. Try hooking it up to a working computer, then shining a bright light on the screen while viewing it from an angle. If you can see the desktop or whatever the computer is displaying, that confirms it.

Hooked it up to a working PC and turned it on. I cannot see any image on the screen when I illuminate it with a flashlight.

Should I perform the tests outlined above or do I go in another direction?

[PlainBill]

Re: Samsung 215tw display cuts out

[QUOTE=almoodie]

Razzy is probably right, it's most likely an inverter / backlight issue. Try hooking it up to a working computer, then shining a bright light on the screen while viewing it from an angle. If you can see the desktop or whatever the computer is displaying, that confirms it.

Hooked it up to a working PC and turned it on. I cannot see any image on the screen when I illuminate it with a flashlight.

Should I perform the tests outlined above or do I go in another direction?

I would say you may have to go in a different direction. However, there are a few things to try first. On most LCD panels you can see if the backlights are on from the back of the panel. If they are off, look at the back of the power supply / inverter. Notice the label by the cable that goes to the logic board. One of those lines controls the brightness of the backlights, the other turns them on and off. It APPEARS the two lines are the ones on the extreme left in the picture. Check if either of those lines changes state when the backlights goes off. If they don't, it IS a backlight / inverter issue, and follow the asteps in the previous post.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

Blacklight comes on when monitor is first switched on but only for a second or so. This process can be repeated over and over.

Transformers
All values relative to ground
Primary resistances (to each of the three legs or the transformer primary)
1.6 ohm 9.0M ohm 9.0M ohm
1.5 ohm 9.0M ohm 9.0M ohm
1.0 ohm 8.13M ohm 8.6M ohm
19 ohm 9.0M ohm 9.0M ohm
7 ohm 7.2M ohm 7.5M ohm
1.4 ohm 7.5M ohm 7.7M ohm

All secondary resistances = 0.89k ohm

All return voltages R1 – R6 = 0.2 V AC

V1 = 0.012 V AC
V2 = 0.012 V AC
V3 = 0.012 V AC
V4 = 0.012 V AC
V5 = 0.012 V AC
V6 = 0.025 V AC


Connector to logic board voltages. Power on, all boards and display connected
ADJ = 0.9 V
GND
GND
GND
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
Analog = 0.6V at switch on, rises to 3V when backlight dies
ON/OFF = 11V at switch on, drops to 3V when backlight dies

Al.

[PlainBill]

Re: Samsung 215tw display cuts out

Blacklight comes on when monitor is first switched on but only for a second or so. This process can be repeated over and over.

Transformers
All values relative to ground
Primary resistances (to each of the three legs or the transformer primary)
1.6 ohm 9.0M ohm 9.0M ohm
1.5 ohm 9.0M ohm 9.0M ohm
1.0 ohm 8.13M ohm 8.6M ohm
19 ohm 9.0M ohm 9.0M ohm
7 ohm 7.2M ohm 7.5M ohm
1.4 ohm 7.5M ohm 7.7M ohm

All secondary resistances = 0.89k ohm

All return voltages R1 – R6 = 0.2 V AC

V1 = 0.012 V AC
V2 = 0.012 V AC
V3 = 0.012 V AC
V4 = 0.012 V AC
V5 = 0.012 V AC
V6 = 0.025 V AC


Connector to logic board voltages. Power on, all boards and display connected
ADJ = 0.9 V
GND
GND
GND
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
13 V = 13.35 V backlight on or not
Analog = 0.6V at switch on, rises to 3V when backlight dies
ON/OFF = 11V at switch on, drops to 3V when backlight dies

Al.

That seems to confirm it. The logic board is shutting down the backlights.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

That seems to confirm it. The logic board is shutting down the backlights.

PlainBill

What can I do now.

[PlainBill]

Re: Samsung 215tw display cuts out

What can I do now.

Post pictures of the logic board. But things aren't looking very good.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

Post pictures of the logic board. But things aren't looking very good.

PlainBill

Images of logic board are attached.

I have another, known-to-be-working, Samsung 215tw, so I took the logic board out and put it in the non-working monitor, results were the same, back light shuts down after a second or so.
Next I put the screen from the non-working monitor in the chassis of the working monitor, so that all components are known to be good with the exception of the screen. Same result, backlight turns on for a second or so then shuts down.
I deduce from this that the screen/backlight of the non-working monitor has a backlight problem.
Do you agree?
I have looked at taking the screen apart to access the CCFL tubes but it is not obvious how it comes apart, any advice.

Al.

[PlainBill]

Re: Samsung 215tw display cuts out

Images of logic board are attached.

I have another, known-to-be-working, Samsung 215tw, so I took the logic board out and put it in the non-working monitor, results were the same, back light shuts down after a second or so.
Next I put the screen from the non-working monitor in the chassis of the working monitor, so that all components are known to be good with the exception of the screen. Same result, backlight turns on for a second or so then shuts down.
I deduce from this that the screen/backlight of the non-working monitor has a backlight problem.
Do you agree?
I have looked at taking the screen apart to access the CCFL tubes but it is not obvious how it comes apart, any advice.

Al.

Good job of troubleshooting. I wish more people were that thorough.

As far as taking the LCD panel apart, same advice as before - post pictures. The disassembly process is often non-intuitive. After all, they really aren't designed to be taken apart.

One final point: Given that the logic card seems to be shutting the backlights down, the most likely source of the problem is the LCD panel, not the CCFLs.

PlainBill

[almoodie]

Re: Samsung 215tw display cuts out

Good job of troubleshooting. I wish more people were that thorough.

As far as taking the LCD panel apart, same advice as before - post pictures. The disassembly process is often non-intuitive. After all, they really aren't designed to be taken apart.

One final point: Given that the logic card seems to be shutting the backlights down, the most likely source of the problem is the LCD panel, not the CCFLs.

PlainBill

I have the screen assembly apart, lots of pieces.
The CCFL tubes look OK as far as I can tell, no breaks or blackening.
I had thought that the screen driver board and the LCD panel would separate but that does not appear to be the case, image attached. If they will not separate then I guess I am out of luck with this LCD panel. I Googled replacement screens but they are priced so high it makes repair uneconomic.
Selling the good boards on Ebay looks the way to go.

Al.

[almoodie]

Re: Samsung 215tw display cuts out

If I connect power/inverter board to the CCFLs, and to the logic board, but do not connect the logic board to the panel (actually the board fused to he panel), and switch on, I get the same backlight on for two seconds the off.

Why does the power/inverter board shut down the CCFLs?
1) Because the CCFLs show over voltage or over current. Makes sense since the power/inverter board IS connected to the CCFLs. This would mean there is a problem with the CCFLs or associated wiring. Is that correct.
2) OR is the the power/inverter board able to detect that that the logic board is not connected to panel board, and hence can shut down for that reason.

I ask because I can't see and problem with the CCFL lamps, no breaks or blackening, and the wiring shows no faults.

If there is no problem with the CCFLs and their wiring, does that mean their must be a problem with the board fused to the LCD panel.

Help, I'm trying to educate myself.

[PlainBill]

Re: Samsung 215tw display cuts out

If I connect power/inverter board to the CCFLs, and to the logic board, but do not connect the logic board to the panel (actually the board fused to he panel), and switch on, I get the same backlight on for two seconds the off.

Why does the power/inverter board shut down the CCFLs?
1) Because the CCFLs show over voltage or over current. Makes sense since the power/inverter board IS connected to the CCFLs. This would mean there is a problem with the CCFLs or associated wiring. Is that correct.
2) OR is the the power/inverter board able to detect that that the logic board is not connected to panel board, and hence can shut down for that reason.

I ask because I can't see and problem with the CCFL lamps, no breaks or blackening, and the wiring shows no faults.

If there is no problem with the CCFLs and their wiring, does that mean their must be a problem with the board fused to the LCD panel.

Help, I'm trying to educate myself.

Assuming I understand how everything works, that is correct. I don't understand what information passes from the panel board back to the logic card, but assuming there is some sort of status information passed that way would account for your observations.

PlainBill

[freelander]

Re: Samsung 215tw display cuts out

The Samsung 215TW shares the same Samsung LTM210M2 panel as Gateway FPD2185W and HP F2105 monitors that I have worked on. Based on your problem description, you almost definitely have one or more dead bulbs in your panel. I'm not sure if this model has the -01 or the -02 variation but the only difference is the connector style. Do you have three individual connectors for each bulb bank? I had a troublesome monitor like this that didn't have any obvious signs of blackening etc but when I individually tested the bulbs, one was indeed dead and causing the shutdown. Upon disassembly, I discovered that the reason I couldn't see any obvious issues is because the solder joint on the bulb failed within the rubber sleeve on the end. Quite unusual failure mode but it happened to me with this panel.

By the way, I have never been able to see an image with a functioning power board and dead bulbs with this panel. I'm not sure if there is some kind of film but just an observation.

I didn't notice if you said that you took the known-to-be-working panel and tried it in the recently repaired monitor. Confirm that your repair is good and you know that you have isolated it.

[almoodie]

Re: Samsung 215tw display cuts out

The Samsung 215TW shares the same Samsung LTM210M2 panel as Gateway FPD2185W and HP F2105 monitors that I have worked on. Based on your problem description, you almost definitely have one or more dead bulbs in your panel. I'm not sure if this model has the -01 or the -02 variation but the only difference is the connector style. Do you have three individual connectors for each bulb bank? I had a troublesome monitor like this that didn't have any obvious signs of blackening etc but when I individually tested the bulbs, one was indeed dead and causing the shutdown. Upon disassembly, I discovered that the reason I couldn't see any obvious issues is because the solder joint on the bulb failed within the rubber sleeve on the end. Quite unusual failure mode but it happened to me with this panel.

By the way, I have never been able to see an image with a functioning power board and dead bulbs with this panel. I'm not sure if there is some kind of film but just an observation.

I didn't notice if you said that you took the known-to-be-working panel and tried it in the recently repaired monitor. Confirm that your repair is good and you know that you have isolated it.

The panel is indeed LTM210M2 L02. Only 2 individual connectors per bank, image attached. I will examine the bulbs carefully tomorrow and report back.

[freelander]

Re: Samsung 215tw display cuts out

The small connector makes it easy to test one connector at a time but you may need to become a little creative with the big one. I have used little pins to make it easy to use aligator clip leads to connect the panel when it is not in place. To verify that you have one or more failed bulbs, you will need to take advantage of your second panel. you can connect disconnect one connector at a time and connect with the similar (known good) connector for a bulb bank in your good monitor. There is a methodical approach here and all that it will do is narrow down your bulbs without removing them yet. Make sure that you power down in between re-arranging your connections and be sure not to short anything out.

You can also remove the larger connector if need be to bare the wire ends. You will notice little tabs that you can push in and very carefully pull the wire out of the connector. Of course, if you can rig something up with what you have on hand without doing that, that works too.

[almoodie]

Re: Samsung 215tw display cuts out

The Samsung 215TW shares the same Samsung LTM210M2 panel as Gateway FPD2185W and HP F2105 monitors that I have worked on. Based on your problem description, you almost definitely have one or more dead bulbs in your panel. I'm not sure if this model has the -01 or the -02 variation but the only difference is the connector style. Do you have three individual connectors for each bulb bank? I had a troublesome monitor like this that didn't have any obvious signs of blackening etc but when I individually tested the bulbs, one was indeed dead and causing the shutdown. Upon disassembly, I discovered that the reason I couldn't see any obvious issues is because the solder joint on the bulb failed within the rubber sleeve on the end. Quite unusual failure mode but it happened to me with this panel.

By the way, I have never been able to see an image with a functioning power board and dead bulbs with this panel. I'm not sure if there is some kind of film but just an observation.

I didn't notice if you said that you took the known-to-be-working panel and tried it in the recently repaired monitor. Confirm that your repair is good and you know that you have isolated it.

Sorry I posted this mesage to the wrong thread last night!!!!!!!!!!!!
Freelander, you are correct, exactly as you said, one of the solder joints at the end of one of the CCFL tubes had failed, presumably leading to arcing. Images are attached.

For those who have never seen the guts of a panel here goes:

Image 1: Essentially a metal tray with a sheet of white glossy plastic in the bottom. The angled pieces (wires attached) lying to the side each carry 3 CCFL tubes. These angled pieces slot in top and bottom in the tray creating a wall of light

Image 2: One of the two angle pieces which carry the CCFLs

Image 3: A 3/8 inch slab of clear plastic which sits in the main panel tray. On top of this sit 3 layers of plastic sheet (not shown). I guess they are polarizers, diffusers, or the like.

Image 4: The failed CCFL return wiring

Image 5: A bank of 3 CCFL tubes with wiring

Image: 6 Closeup of CCFL ends with charring. White end piece is rubber and broken up somewhat with the charring.

All the pieces are quite robust but I had to get my 17 year old daughter with her small hands to disassemble to CCFLs from the angle pieces. Have to go get some wire fine enough to rewire the CCFLs tomorrow, together with a can of compressed air and a microfiber cloth, the poor man's answer to a clean room.

This is all very interesting but probably an uneconomic exercise. Plus the big question is whether I can put this thing back together in an acceptable state of cleanliness such that I get a usable monitor.

[freelander]

Re: Samsung 215tw display cuts out

Glad to see that you found it. Since you are about to move this to the bone pile, you should consider trimming the end of the lead and re-solder to the tube bank. It certainly isn't an ideal solution but I brought one back to life this way and it's still running.

[almoodie]

Re: Samsung 215tw display cuts out

I need to rewire the return leads to the CCFLs, shown in attached image. I've tried Radio Shack my only local retailer but can find anything of suitable gauge. Can anyone tell me what gauge wire I need and where I might order it, a part number would be of great help.

Al.