Samsung LCD - Weird Failure - Trying to Repair - Page 1
Forum section: electronics / repair

author: katzohki
author_rank: Frequent Contributor
timestamp: June 23, 2014, 07:48:20 pm
content: I have a weird failure with this Samsung 215TW. Let me start off by stating what I've done:I replaced the bad caps (bloated CapXon) on the power supply board and checked voltages at the local regulators. Everything looks good with voltage, but no fix yet. I also checked over the main board for bad solder joints and other physical maladies.Here's a picture of the strange glitch:As you can see, it looks pretty scrambled. Thisshouldbe something like a message stating "no source found" or something like that. It floats around the screen. And when I try to change inputs, it pops up into the upper-left corner where the input message box would normally be. Besides that, I haven't got video when testing the inputs. To be fair, and you can beat me up over this if you want, I have only tested the VGA input. But I really don't think that's going to be the issue because something looks wrong besides input. I'm thinking it's a communications issue somewhere on the main board. There is a service manual available online that details the schematics of the monitor.Any ideas?

author: AndyC_772
author_rank: Super Contributor
timestamp: June 23, 2014, 07:51:55 pm
content: Looks like there's some dual port RAM that's not getting written.

author: katzohki
author_rank: Frequent Contributor
timestamp: June 23, 2014, 08:07:01 pm
content: Hm, there's a 128M SDRAM chip, but it looks like the only thing writing to it is the main ADC / Prescaler / LVDS. I'll see if I can give it a probe.

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: June 23, 2014, 09:24:24 pm
content: It looks like the eeprom is corrupt to me .

author: tautech
author_rank: Super Contributor
timestamp: June 23, 2014, 09:32:45 pm
content: In VGA source mode are you supplying a PC video signal?Maybe your card won't recognize it?What was the original fault?

author: katzohki
author_rank: Frequent Contributor
timestamp: June 24, 2014, 07:07:34 pm
content: Yeah, I'm afraid it might be a corrupt EEPROM or firmware.To answer tautech's questions:Yes, supplied VGA from PCIt does this even unplugged, so don't think source is the issue.Original fault was this, I inherited it. It's really a nice monitor that I'd love to fix, but eh if it's beyond economical repair I've only spent a few bucks on caps so far.

author: onlooker
author_rank: Frequent Contributor
timestamp: June 26, 2014, 11:53:43 am
content: I think the easist fix is to get a universal lcd tv logic board. On ebay an hdmi one with remote ctrl is about $12 (search for hdmi universal lcd board). The VGA only ones are about $6 each. The rest will be mostly mechanically fiting it to you monitor and rerouting the power supply.

author: urbis
author_rank: Unknown
timestamp: June 27, 2014, 10:34:44 am
content: On Samsung TVs, when the caps fail, it's notorious for corrupting the EEPROM.There may be a reset by shorting a couple of pins, but not entirely sure.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: June 27, 2014, 06:52:30 pm
content: Jackson Pollock eat your heart out.On a more serious note - does the pattern vary? I don't mean the location on the screen, or its overall size. From what I can see there is a repetitive block pattern.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 27, 2014, 07:32:47 pm
content: Quote from: urbis on June 27, 2014, 10:34:44 amLike this?http://www.badcaps.net/forum/showpost.php?p=305868&postcount=8

author: katzohki
author_rank: Frequent Contributor
timestamp: June 27, 2014, 07:40:11 pm
content: Quote from: Dave Turner on June 27, 2014, 06:52:30 pmYes, beside the fact that it tracks around the screen in "screensaver mode" the squares change a tad and pixels switch on and off. It doesn't seem like COMPLETELY random data, which is why I'm leaning towards the EEPROM as well...Quote from: retiredcaps on June 27, 2014, 07:32:47 pmI've seen that, but when I press menu it is scrambled too. I want to try it, but I can't confirm the OSD menu! I guess maybe I can try to sort of guess my way through it...

author: Dave Turner
author_rank: Frequent Contributor
timestamp: June 27, 2014, 11:57:52 pm
content: I couldn't do it now, 'cos I don't know the system but back in the day of 8 bit micros you could sort of read the pattern in hex. Whilst more complex the same holds true now.In this instance the question is whether a stable pattern helps point to the solution or is it irrelevant?

author: Rasz
author_rank: Super Contributor
timestamp: June 30, 2014, 08:07:18 am
content: My main monitor is a Belinea 21' that does similar thing on VGA, but works perfectly on DVI. When on DVI and with 1:1 mapping video is bypassing scaler completely. Try dvi before going further, even with corrupted flash or bad memory there is a chance it will work.http://www.d43d.ru/forums/index.php?/gallery/image/1357-samsung-215tw/http://img03.taobaocdn.com/bao/uploaded/i3/T1M9Y0XoNkXXaoqCvb_094912.jpghttp://remont-aud.net/_fr/86/4958775.jpgas for the fault I dont think its flash, even solid background is corrupted on your picture. Check lvds cables, freeze/heat/tap ram chip.

author: tautech
author_rank: Super Contributor
timestamp: June 30, 2014, 08:41:50 am
content: I got given a nice little widescreen 24" TV that had a similar complaint, saved from a skip on a hunch.Problem was found when data cable to LCD was removed and re-seated.Still going strong 2 years later.