Samsung SyncMaster Model 731N Distorted Display

[jayoung]

I received a Samsung SyncMaster 731N today from the local computer store. Monitor functions as expected, but the image is distorted horizontally (see images). I took apart the monitor, and swapped out the lcd panel and the ribbon cable to the lcd panel with no change. Multiple computer inputs and cables have been utilized. As you can see in the image, the OSD appears normal.

Nine capacitors on the power / inverter board are all Su'scon. On the video board, four capacitors are Su'scon and six capacitors are TEAPO.

There are several threads on badcaps.net for this monitor, but they are for no display.

Anybody have any ideas what could be causing this? Thanks in advance.

I can get and attach pictures of the power / inverter board and / or the video board if needed.

[PlainBill]

Re: Samsung SyncMaster Model 731N Distorted Display

I received a Samsung SyncMaster 731N today from the local computer store. Monitor functions as expected, but the image is distorted horizontally (see images). I took apart the monitor, and swapped out the lcd panel and the ribbon cable to the lcd panel with no change. Multiple computer inputs and cables have been utilized. As you can see in the image, the OSD appears normal.

Nine capacitors on the power / inverter board are all Su'scon. On the video board, four capacitors are Su'scon and six capacitors are TEAPO.

There are several threads on badcaps.net for this monitor, but they are for no display.

Anybody have any ideas what could be causing this? Thanks in advance.

I can get and attach pictures of the power / inverter board and / or the video board if needed.

I would suspect a problem on the signal (video) board, probably in the video input circuitry.

PlainBill

[jayoung]

Re: Samsung SyncMaster Model 731N Distorted Display

I would suspect a problem on the signal (video) board, probably in the video input circuitry.

PlainBill

Anything in particular to check?

[PlainBill]

Re: Samsung SyncMaster Model 731N Distorted Display

Anything in particular to check?

I'd check voltages on U101 and U102 - the LDO regulators. I'm going on the belief that there is noise on the analog input signal, so the caps are also suspect.

PlainBill

[jayoung]

Re: Samsung SyncMaster Model 731N Distorted Display

U101:
A1
AS117L-33
BO637 26
Pin 1 - 0.00 VDC
Pin 2 - 3.30 VDC
Pin 3 - 5.16 VDC
Pin 4 - 3.30 VDC

U102:
A1
AS117L-18
BO552
Pin 1 - 0.00 VDC
Pin 2 - 1.39 VDC
Pin 3 - 5.15 VDC
Pin 4 - 1.39 VDC

I had to order some parts from digikey.com for another job, so I ordered replacements for the 10 capacitors on the signal board at the same time. I was also thinking that there may be noise from 1 or more of the capacitors causing the issue. I see that the voltage on U102 is low also (1.39 VDC vs. 1.80 VDC). Not sure if that is from a defective regulator or not?

[retiredcaps]

Re: Samsung SyncMaster Model 731N Distorted Display

AS117L-18

I see that the voltage on U102 is low also (1.39 VDC vs. 1.80 VDC). Not sure if that is from a defective regulator or not?

Definitely defective. A voltage regulator should be within 1% of its specs. In this case,

1.8 x 0.99 = 1.782
1.8 x 1.01 = 1.818

[jayoung]

Re: Samsung SyncMaster Model 731N Distorted Display

I've tried finding a replacement for this part, but have not not been able to find an exact match to the part number. I have found AMS1117-18, LD1117-18, LM1117-18, L1117-18, etc., but no AS117L-18.

I think this is the datasheet for the original regulator:
http://www.alldatasheet.com/datashee...A/AS1117.html?

Would this part be a possible replacement? I may be able to call digikey.com tomorrow morning and get this added to my order.
http://search.digikey.com/us/en/prod...9-5-ND/2472287

Thanks in advance!

[retiredcaps]

Re: Samsung SyncMaster Model 731N Distorted Display

I have found AMS1117-18, LD1117-18, LM1117-18, L1117-18, etc., but no AS117L-18.

Any of those will work. Just make sure the size/package is correct. They are "jellybean" parts and made by a lot of different manufacturers.

[PlainBill]

Re: Samsung SyncMaster Model 731N Distorted Display

I'm going to throw a warning out here. At this point the best option is to replace the regulator. However, there is a significant chance the regulator is fine, something is loading down the output.

PlainBill

[jayoung]

Re: Samsung SyncMaster Model 731N Distorted Display

The ten capacitors and the replacement regulator are on order with digikey.com and should arrive in a day or two. Is is worth replacing the regulator and checking the outcome or should I go ahead and replace the capacitors along with the regulator?

[PlainBill]

Re: Samsung SyncMaster Model 731N Distorted Display

The ten capacitors and the replacement regulator are on order with digikey.com and should arrive in a day or two. Is is worth replacing the regulator and checking the outcome or should I go ahead and replace the capacitors along with the regulator?

Regulator first. I don't think a bad cap (or caps) would explain that unusual voltage.

PlainBill

[sabre504]

Re: Samsung SyncMaster Model 731N Distorted Display

Did you check the input voltage to the regulator ?

Scratch that i see you were getting 5+ volts on input was it steady ?

[jayoung]

Re: Samsung SyncMaster Model 731N Distorted Display

Did you check the input voltage to the regulator ?

Scratch that i see you were getting 5+ volts on input was it steady ?

Yes, the input voltage on both regulators was steady.

[jayoung]

Re: Samsung SyncMaster Model 731N Distorted Display

Success!

Ordered arrived from digikey.com today and I replaced the 1.8V regulator. Plugged everything in and the voltage was steady at 1.80VDC and the picture is crystal clear with no distortion. Thanks everyone.

[trains58554]

Re: Samsung SyncMaster Model 731N Distorted Display

Hi All,

I have the exact same problem. I was wondering if I could use an ez1117 as the replacement for the as1117-18

Thanks

[jetadm123]

Re: Samsung SyncMaster Model 731N Distorted Display

Hi All,

I have the exact same problem. I was wondering if I could use an ez1117 as the replacement for the as1117-18

Thanks

For the as1117-18, the "-18" indicates a fixed output of 1.8 volts. Since there is nothing after the ez1117, then I'm assuming the output voltage has to be set using external resistors.

[trains58554]

Re: Samsung SyncMaster Model 731N Distorted Display

Hi jetadm123,

Thanks for your reply there where no other numbers at the end and I did a little more reading and I think you are right about it needing external resistors.

Thanks

[trains58554]

Re: Samsung SyncMaster Model 731N Distorted Display

Does anyone by any chance know of any devices that have this chip in them?

Is the 1117m3 compatible?

Thanks

[retiredcaps]

Re: Samsung SyncMaster Model 731N Distorted Display

Why not just use the part number provided in post #7 at digikey?

[trains58554]

Re: Samsung SyncMaster Model 731N Distorted Display

I will probably just end up ordering it from digikey but I figured that it does not hurt to look at the parts I have laying around.