Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

[alien_]

Hi there,

My Samsung LE37B550A5W suddenly started showing a distorted picture yesterday, I would really appreciate your thoughts on the problem.

Fault description: The picture went very dark and high contrast. The image seems slightly noisy and everything has a glowing white outline (see comparison) and there's an apparent horizontal ghosting (the horizontal lines follow the movement of program windows, the cursor, etc). The refresh rate seems to be down as well The fault is apparent across the menus and all input I could test (there's no cable attached, so I couldn't check that).
When I turn on the TV after leaving it standing for a while it starts up showing the issue, but gradually it gets even darker within less than a minute.

The display was used as my primary display for my desktop PC from 2009, so it has a lot of mileage.

Do you think it's a dried out capacitor, something on the T Con board or something different?

Thanks in advance!

Pictures attached below:

[tom66]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

Can't see your pictures at work, but from your description I'd say AS15-F gamma IC fault. Can you supply a picture of your T-con (if you have not already)?

[alien_]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

Can't see your pictures at work, but from your description I'd say AS15-F gamma IC fault. Can you supply a picture of your T-con (if you have not already)?

Hi Tom,

Thanks for the super quick reply! I've attached a picture of my T-con below.
The gamma IC version is AS15-HF on mine.


This is the only UK seller I found (would rather not order from China this time as I need it up and running as soon as possible, it's essential for me to have 2 displays for 3D modelling), does it seem to be the right part?
http://www.ebay.co.uk/itm/AS15-HF-E-...item2ecb993a34

[tom66]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

I can't imagine using two 37" displays as monitors for a PC... 2 x 24" is too big for my desk! Do you wall mount them?

You can try testing the VGAMMA voltage points.

You will need a digital multimeter.

Set the meter to the 20 DCV range (20 DC volts range) or auto ranging DC volts (if available)

With the board installed in the chassis and the TV powered on, with an image on the screen (does not matter what image):
- Put black probe of meter onto exposed metal on chassis. The wall mount fixings are a good option. You may need an assistant to hold.
- Touch red probe to the points marked VG1 through VG22. (Not all may be available.) VG1 and VG2 are near the top left ribbon connector (bottom right in your photo.)
- Report voltage measured on each VG point. We can tell you if they are good or bad.
- A general rule of thumb for VG voltages (gamma curve/VGAMMA voltages): they should rise OR fall, but only one way. e.g. 1,2,4,7,9V is OK. 9,7,4,2,1V is OK, but 1,3,2,7,4V is a FAIL. (Sequence should be MONOTONIC.)

If it FAILs then you can replace AS15-F IC but it is an moderately advanced level soldering project. It took me a few attempts to get right, but it fixed a Sony TV of mine.

You can use any AS15 to replace any AS15. These should work:
http://www.ebay.co.uk/sch/i.html?_fr...c&LH_PrefLoc=1

[alien_]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

I'm running an odd setup with a 37" display for generic use and a 22" Wacom for digital painting and sculpting. I'd love to screw the telly on the wall behind the drawing tablet but unfortunately, the landlord would not have anything on the wall.

I'll check the measurements tomorrow and get back with the results!

I haven't done any board repair since I left my previous job, but I'll try to borrow a heat gun, hopefully I didn't forget how to use it

[alien_]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

The measurements are as follows:
---------------
VG1=6.97*
VG2=7.68
VG4=7.65
VG6=7.6
VG8=7.6
VG10=7.57
VG11=7.57
VG12=6.64
VG13=6.87*
VG15=4.87
VG17=4.15
VG19=2.85
VG21=0.52
VG22=0.29
---------------
It's fairly consequent apart from two deviations: VG1 and VG13, the numbers are confirmed by two multimeters. It seems faulty, but could you confirm my conclusion?

[alien_]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

I can't imagine using two 37" displays as monitors for a PC... 2 x 24" is too big for my desk! Do you wall mount them?

You can try testing the VGAMMA voltage points.

You will need a digital multimeter.

Set the meter to the 20 DCV range (20 DC volts range) or auto ranging DC volts (if available)

With the board installed in the chassis and the TV powered on, with an image on the screen (does not matter what image):
- Put black probe of meter onto exposed metal on chassis. The wall mount fixings are a good option. You may need an assistant to hold.
- Touch red probe to the points marked VG1 through VG22. (Not all may be available.) VG1 and VG2 are near the top left ribbon connector (bottom right in your photo.)
- Report voltage measured on each VG point. We can tell you if they are good or bad.
- A general rule of thumb for VG voltages (gamma curve/VGAMMA voltages): they should rise OR fall, but only one way. e.g. 1,2,4,7,9V is OK. 9,7,4,2,1V is OK, but 1,3,2,7,4V is a FAIL. (Sequence should be MONOTONIC.)

If it FAILs then you can replace AS15-F IC but it is an moderately advanced level soldering project. It took me a few attempts to get right, but it fixed a Sony TV of mine.

You can use any AS15 to replace any AS15. These should work:
http://www.ebay.co.uk/sch/i.html?_fr...c&LH_PrefLoc=1

Replacing the AS15-F has fixed the problem, my TV is up and running again Thank you so much Tom, you are ace!

[tom66]

Re: Samsung LE37B550A5W - Dark, high contrast, horizontally ghosting image

Great to hear!
Missed your post, but yes, your voltages are bad. That one is a tricky one: it only loosly breaks the rule. A typical gamma curve should go from approx 0.5V to 14.5V, so it is definitely bad.