Samsung Syncmaster 215TW, power on, no video

[Elmojo]

Hi all,

After my wildly successful first foray into LCD repair with mucho guidance (aka hand-holding!) from PlainBill, I've decided to try once again.
One of my clients had this Samsung in his office for about 3 years. Over time, it developed an odd magenta vertical line a little left of center.
It apparently didn't bother him too much, because he kept using it.
Later on, it got where it would flicker sometimes. Then the screen started to "jump and shake" for lack of a better term.
Finally, it died completely and was replaced.
So I got it as a project, like I need another one!
Now, when I power it on, I get the blue power LED on the front, and if it's connected to a PC, windows detects it as a second monitor. It even picks up the model name and allows me to set the resolution, etc...
However, I get zero picture, nada.
Of course at first I would have suspected a bad backlight or inverter, but I saw the slow progression from bad-to-worse-to-dead.
Oh, I also tried shining a light on it from various angles to see if the backlight had indeed failed, no picture.

I guess my first question would be is this monitor even worth trying to fix?
Could something fairly simple cause the gradual failure that I witnessed, or are we looking at a blown logic board or whatever these things have?

Thanks in advance for any advice,
Mike P.

[Wrog]

Re: Samsung Syncmaster 215TW, power on, no video

I guess my first question would be is this monitor even worth trying to fix?
Could something fairly simple cause the gradual failure that I witnessed, or are we looking at a blown logic board or whatever these things have?

Since you got it for free, I'd say it's definitely worth trying to fix.. especially if you have a use for it.

First off, check the caps and replace any/all suspect brands. Even if something else is wrong, it's best to replace them while you have it open anyway. It also could be as simple as a fuse on the inverter blowing.. check those for continuity first (open = replace). Could be a bad inverter driver (test between legs for shorts) or a voltage regulator that's going/gone bad (measure DC voltage between the center tab and ground).

Standard procedure around here is to post top/bottom of the power supply, inverter and logic boards. Lots of knowledgeable folks around that can spot things quickly and make suggestions.

[Elmojo]

Re: Samsung Syncmaster 215TW, power on, no video

Okay, so you think that even with the very strange "failure signs" that I saw before the monitor died completely, it could still be fixable without replacing any major components?
I just want to be sure I'm not totally wasting my time before I crack this thing open.
Also, I'm going to need much more specific instructions about testing the different components, but we'll get to that later.
Thanks!
Mike P.

[Elmojo]

Re: Samsung Syncmaster 215TW, power on, no video

Well, in the vacuum of responses, I decided to go ahead an crack it open.
I got it disassembled down to the 2 main boards, and found that several of the caps on the power board are bulged. I'll assume they're dead and go ahead and replace all the caps on that board, there's only 7, including the large power cap.
If anyone has input on what else I need to be checking, please share.

[Wrog]

Re: Samsung Syncmaster 215TW, power on, no video

Okay, so you think that even with the very strange "failure signs" that I saw before the monitor died completely, it could still be fixable without replacing any major components?

The magenta line, probably not (panel problem).. but the rest, sure.

[Wrog]

Re: Samsung Syncmaster 215TW, power on, no video

Well, in the vacuum of responses, I decided to go ahead an crack it open.
I got it disassembled down to the 2 main boards, and found that several of the caps on the power board are bulged. I'll assume they're dead and go ahead and replace all the caps on that board, there's only 7, including the large power cap.
If anyone has input on what else I need to be checking, please share.

Large one generally doesn't need to be replaced (unless visibly bad). Top/bottom pics would be great (power, inverter, main/logic)!

[retiredcaps]

Re: Samsung Syncmaster 215TW, power on, no video

I like testing all the transistors, fuses, transformers with resistance tests.

While they may not be bad, it is fairly easy to check and it can be done quickly.

If anyone has input on what else I need to be checking, please share.

[Elmojo]

Re: Samsung Syncmaster 215TW, power on, no video

I like testing all the transistors, fuses, transformers with resistance tests.

While they may not be bad, it is fairly easy to check and it can be done quickly.

That sounds prudent.
How do I test them?
I'm not even sure I could identify them, let alone test them!
If I post a photo of the board, could you call each item out and tell me what value each should test out at?
I have good photos of the board, but it's too late to post them tonight.
I'll add 'em as soon as I can.
Thanks for the help,
Mike P.

[el3ctroded]

Re: Samsung Syncmaster 215TW, power on, no video

Transistors are usually marked by U and will have 3 legs. They come in many varieites, but your most likely culprits are the larger ones mounted to heatsinks. With a DMM on Resistance, check for shorted transistors.

Fuses are marked with an F. They should read a very low resistance. The come in a variety of shapes and sizes. Just look for F designators on the board, usually around the power connector, but not always.

Diodes are marked with a D. use the Diode test on a DMM. Diodes often read 0.2x, 0.5x, or 0.7x when good, depending upon the type of diode. Also, test them both directions (swap DMM Leads). They should not read anything in the opposite direction. If they do, they are either bad, or surrounding circuitry is affecting the reading.

Transformers are the bigger devices with wire wrapped around them. Resistance on certain sets of pins should be low (10-50ohms), and on other sets of pins should be higher (often around 500ohms to 2k, depending upon the transformer). The trick here is if there are 2 identical transformers, compare readings between the two. Sometimes a transformer will have more than 4 pins, but only 4 will be used. It can be confusing.

[Elmojo]

Re: Samsung Syncmaster 215TW, power on, no video

Thanks, that's good info!
I'll test as many of those as I can find and report back.
My replacement caps shipped today, so hopefully I'll be able to reassemble and test soon.

[Elmojo]

Re: Samsung Syncmaster 215TW, power on, no video

Okay, update time.
I haven't had time to test the other components as suggested.
However, the new caps came today and I got those installed.
I popped it back together and powered up.
Now I have the blue power light, and I can tell the backlight is on, which I don't think I had before.
I still get no video and no on-screen menus either.
Do I need to go back and test the other parts as suggested above, or does having the backlight on eliminate those as a possible issue. If so, should I be suspecting a blown logic board and scrap this thing or is it worth it to keep digging?

Thanks in advance,
Mike P.

[retiredcaps]

Re: Samsung Syncmaster 215TW, power on, no video

Do I need to go back and test the other parts as suggested above, or does having the backlight on eliminate those as a possible issue.

Be more specific. Does the backlight flash and you can see the screen for 2 seconds? Did you have a source plugged in?

One of the reasons I test all the components even though the problem might be an obvious blown cap is that some LCDs are very difficult to take apart with fragile connectors. Testing them first gives me confidence that I don't have to take it apart later.

Additionally, the more you test and take measurements for a good working board, you will know what to expect on the next repair.

If so, should I be suspecting a blown logic board and scrap this thing or is it worth it to keep digging?

Fixing it all depends on your will. We don't have pics and no DMM measurements. All these things that were asked for in earlier posts.

[alexanna]

Re: Samsung Syncmaster 215TW, power on, no video

[QUOTE=Elmojo]Hi all,

Now, when I power it on, I get the blue power LED on the front, and if it's connected to a PC, windows detects it as a second monitor. It even picks up the model name and allows me to set the resolution, etc...
However, I get zero picture, nada.


one quick question here are you still hooked up as second monitor?
possibaly try hooking up as primary monitor and power on computer with just the samsung hooked up.
Also verify you have hooked up the 30 pin ribbon cable correctly,I almost hate to admit this but it is possible to connect it upside down to the lcd.
Al.