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Old 09-22-2013, 02:57 PM   #1
ITguy
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Default Samsung LN46A630M1F too bright/white

Hi, and thanks in advance for any help/troubleshooting advice you can offer.

My Samsung LN46A630M1F LCD TV is displaying all input sources and the menu in a global white haze (see attachments). It looks as though someone turned the brightness all the way up, but that's not the case. I've performed both a "reset picture settings" from the regular menu and a factory reset from the service menu. The brightness persists throughout both the PATT_AfterDDR and PATT_BeforeDDR patterns in the service menu's FRCM_Option submenu. I looked at budm's Basic_LCD_TV_trouble_shooting_guide, but I'm not sure if my TV's T-CON board is dead because the picture in his guide shows the screen as all white with no visible input source, while my screen is mostly white with the input source still visible.

I verified that the LVDS cables are all securely connected. I found this video and tried alternately disconnecting the T-CON ribbon cables to see what would be displayed onscreen. Based on the results (see attachments), it seems like the LCD panel is physically capable of displaying input without the excessive whiteness/brightness, although the picture still displayed too brightly towards the left and right edges of the screen. I also disconnected the LVDS cable between the main board and the FRCM - at least I think that's what it's called - and the screen displayed all black with no apparently excessive brightness.

I'm thinking there's a problem with the T-CON board, but I don't know if I really should be arriving at that conclusion based on the evidence collected so far. Even if I'm right, I don't know if I should try to replace the entire T-CON or repair whatever is malfunctioning on it. So I'm VERY interested in hearing opinions from all you experts who have diagnosed more LCD TV problems than me! Please let me know if you have any suggestions or troubleshooting/fact-finding procedures you think I need to perform.

EDIT: An additional piece of information I originally failed to include.... I got this TV used from a friend. When I removed the rear cover for the 1st time, I noticed the metal housing that I think is supposed to be covering the T-CON was simply not there. I'm assuming its purpose would be to protect/shield the T-CON, so maybe its absence contributed to T-CON failure?
Attached Images
File Type: jpg white input.jpg (425.9 KB, 33 views)
File Type: jpg white menu.jpg (472.1 KB, 37 views)
File Type: jpg left (from rear) T-CON ribbon cable disconnected.jpg (171.3 KB, 29 views)
File Type: jpg right (from rear) T-CON ribbon cable disconnected.jpg (296.3 KB, 34 views)
File Type: jpg T-CON (flash).jpg (788.7 KB, 38 views)
File Type: jpg T-CON (no flash).jpg (550.4 KB, 41 views)

Last edited by ITguy; 09-22-2013 at 03:02 PM.. Reason: additional information
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Old 09-22-2013, 03:29 PM   #2
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Default Re: Samsung LN46A630M1F too bright/white

Defective gamma IC in my opinion - found on t-con.

You will need a multimeter to test.

To test: Multimeter on DC 20V or DC Volts autorange.

Each point marked VGMA1 thru VGMA12 to be measured.

Red probe on test point, black probe on chassis.

Readings should be monotonic, they should either increase or decrease but not both.

Also test VCOM point, should be around 7 to 8V.
Attached Images
File Type: jpg vgma2.jpg (611.9 KB, 35 views)
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Old 09-22-2013, 03:51 PM   #3
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Default Re: Samsung LN46A630M1F too bright/white

Ok - will do and report findings. Maybe stupid question: should TV be powered on while testing?
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Old 09-22-2013, 04:03 PM   #4
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Default Re: Samsung LN46A630M1F too bright/white

Yes it should, I forgot to say so. Powered and showing fault on both halves.
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Old 09-22-2013, 05:37 PM   #5
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Default Re: Samsung LN46A630M1F too bright/white

that sure looks like a tcon problem to me I ran into the same problem same tv replaced tcon all was good
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Old 09-22-2013, 07:50 PM   #6
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Default Re: Samsung LN46A630M1F too bright/white

Tom, here are the voltage readings I got on my multimeter....
VGAMA1: 14.84
VGAMA2: 15.78
VGAMA3: 15.86
VGAMA4: 15.19
VGAMA5: 14.80
VGAMA6: 15.37
VGAMA7: 7.11
VGAMA8: 4.99
VGAMA9: 4.51
VGAMA10: 3.59
VGAMA11: 2.04
VGAMA12: 391 (mV)
VCOM: 6.08

Based on what you said about how the readings should be monotonic and how the VCOM reading is expected to be 7-8V, my results support your hypothesis of the T-CON having a defective gamma IC, right? Can this specific IC be replaced independent of the entire T-CON?
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Old 09-22-2013, 07:57 PM   #7
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Default Re: Samsung LN46A630M1F too bright/white

Just have to start looking up the spec sheet of the ICs to find out which one is used for generating the GAMMA ref voltages. A lot of T-CON board uses AS15xx, not sure what your board is using.
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Old 09-22-2013, 09:12 PM   #8
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Default Re: Samsung LN46A630M1F too bright/white

Thanks. I follow the logic of what you're saying, but I have no practical experience doing this so I'm kind of lost trying to find the correct resources. I tried searching for a spec sheet on my T-CON to figure out which ICs are on it....but I failed. Any suggestions? Or should I just start removing the thermal pads on the T-CON to see what's underneath them? I didn't see anything AS15xx elsewhere on the board.
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Old 09-22-2013, 09:19 PM   #9
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Default Re: Samsung LN46A630M1F too bright/white

Yes, you need to read what are printed on the top of the ICs, then Google those numbers to see what you will come up with. Did you look around to see how much the repalcement T-CON board will be? By the time you invest money on proper tools for SMD repair, you may be better off changing the board.
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Old 09-22-2013, 09:19 PM   #10
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Default Re: Samsung LN46A630M1F too bright/white

@freakaftr8: Thanks for sharing your experience! I'm putting off shelling out $75 for pulled T-CON from eBay as long as possible....at least until feasibility of fixing current T-CON approaches zero.
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Old 09-23-2013, 02:15 AM   #11
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Default Re: Samsung LN46A630M1F too bright/white

Quote:
Originally Posted by ITguy View Post
@freakaftr8: Thanks for sharing your experience! I'm putting off shelling out $75 for pulled T-CON from eBay as long as possible....at least until feasibility of fixing current T-CON approaches zero.
well my hats off to you! I've never successfuly repaired a t-con board before but I wish you luck.
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Old 09-23-2013, 02:20 AM   #12
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Default Re: Samsung LN46A630M1F too bright/white

That gamma IC is definitely defective.

Here is some info on LCD gamma curves, you can see VG1 thru VG16 as an example on page 175.
http://cdn.intechopen.com/pdfs/11273..._ic_design.pdf

You may be able to replace it depending on if the gamma IC is readily available.
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Old 09-23-2013, 07:04 PM   #13
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Default Re: Samsung LN46A630M1F too bright/white

Thanks for the info. Since I have little soldering experience and no hot air rework equipment as recommended here, I've decided to just replace the T-CON board. (Thanks for putting me onto that, budm.) There's a local guy on craigslist who's said he'll get back to me about whether or not he has the board I'm looking for. Otherwise, I'm thinking of picking up this one on eBay.
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Old 09-23-2013, 07:09 PM   #14
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Default Re: Samsung LN46A630M1F too bright/white

There's a guy on eBay repairing similar T-con boards with the same fault for less -- perhaps consider asking him?
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Old 09-23-2013, 07:45 PM   #15
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Default Re: Samsung LN46A630M1F too bright/white

Oh, that's a good idea! I saw a listing for someone offering to repair my specific board for $75, but I didn't think to look for someone offering to repair T-CON boards in general. I like the thought of paying less....
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Old 10-07-2013, 09:31 PM   #16
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Default Re: Samsung LN46A630M1F too bright/white

Just want to update you all....
I shipped my T-Con to a guy on eBay after confirming he was willing to replace the gamma IC. Received the repaired board in the mail today, popped it back into my TV, and the picture's back to normal!! I'm very happy about that (and only a little disappointed I wasn't able to do the repair myself). Also, I'm grateful to you guys for helping me to diagnose the problem and figure out how to resolve it!
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Old 10-08-2013, 02:15 AM   #17
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Default Re: Samsung LN46A630M1F too bright/white

Thanks for repair feedback, out of interest, how much did that service cost?
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Old 10-08-2013, 10:14 AM   #18
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Default Re: Samsung LN46A630M1F too bright/white

$50.
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