LG 37LG10-UM has grey screen color and ghosting

[axlmastr]

I have a friend's LG3710-UM Prod date Dec 2008 to look at.

When turned on the screen is light grey with a sort of ghosting effect when the "no signal" icon dances around the screen. All four corners of the panel have pulled in a bit showing radiused corners. Close look at the middle area shows markings in the grey color that look like "bicycle treads" running at angles.

When signal to fed through it looks as though it is in black and white though more greyscale and weak at that.

Cursory look at boards reveals Taicon on power supply and all look good. There is a notable buzz from the inverter board.

Just wondering where to look for issues. I did have a spare power board which I recapped with Panasonic FC and/or FM with no change.

[sordids999]

Re: LG 37LG10-UM has grey screen color and ghosting

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[axlmastr]

Re: LG 37LG10-UM has grey screen color and ghosting

Thanks. It's not my first rodeo here. I've been busy with other projects to take the pictures. They'll be up later today. Didn't really expect a response.

[axlmastr]

Re: LG 37LG10-UM has grey screen color and ghosting

Pics posted

[Andrew F. Ali]

Re: LG 37LG10-UM has grey screen color and ghosting

I would think backlight issue...one or two of the CCFL may be weak....or the Inverter circuitry has a fault transformer/coil...or component.

[axlmastr]

Re: LG 37LG10-UM has grey screen color and ghosting

Thanks for the reply, but if it were backlight then the screen would be dark and the image would need to be seen with a flashlight. The image is quite bright so backlight is not an issue. Though I mentioned some buzzing from the inverter board is is working since it is firing the bulbs.

The issue is lack of color from the panel (very monochrome) and the ghosting effect is an additional issue. That I would say is more of a logic/main board or bad LVDS cable or connection. I have two other logic/main boards to sub in.

Attached are some pics of a recapped logic/main board I have and the reverse side of that board as well as what the display looks like with a signal through it.

[diif]

Re: LG 37LG10-UM has grey screen color and ghosting

I'd suspect the AS15 chip on the tcon, measuring the gamma voltages would confirm this.

[budm]

Re: LG 37LG10-UM has grey screen color and ghosting

+1 check the GAMMA ref. dc Voltages to start with.

[axlmastr]

Re: LG 37LG10-UM has grey screen color and ghosting

Okay I'm game. How would I measure the gamma voltages?

[diif]

Re: LG 37LG10-UM has grey screen color and ghosting

It looks to be the two rows of copper pads at the top just to the right of the sticker.

[axlmastr]

Re: LG 37LG10-UM has grey screen color and ghosting

These two rows are marked XPOL_1 & XSTB_1. The top row has a "B" before it.

Here's the voltages:

Top Row L-R: 15.56; 15.51; 15.49; 14.08; 15.39; 15.13; 1.05; 0.18
Bottom Row L-R: 15.50; 15.42; 15.50; 15.47; 13.65; 15.29; 0.34; 1.63

Over to the right of the rows is a triangle of pads marked YDIOU_1; YOE_1; YCLK1. I can't tell which mlabels apply to which pads but the readins are: 0.0 for the upper left, 2.08 for the upper right, 0.28 for the bottom center.

According to the legend on the PCB the top row L-R is VGamma 21, 16, 13, 11, 8, 6, 1. Bottom row L-R is VGamma 22, 17, 15, 12, 10, 7, 2. Odd that there are 8 pads per row and only markings for 7 per row.

If it turns out to be the A15-U IC then I can change it.

[Alastair E]

Re: LG 37LG10-UM has grey screen color and ghosting

Run set for 5 mins.

Bung finger on AS-15.

If it burns--Change it! (AS-15, Not finger....)

[axlmastr]

Re: LG 37LG10-UM has grey screen color and ghosting

Ran it for 5 min

Touched top of IC with the tip of my finger to a count of 2 sec and.... OWWW! Hot like you said it might be.

Used one of those handheld laser thermometers to get as close to an accurate reading as possible.... approx 109 F or 41-42 C temp.

Not that I have any but would freeze spray or using compressed air from my air compressor pointed directly at the top of the IC show any difference to performance? Still going to change the IC if that is what you advise, but wondering if a targeted cooling would change behavior.

[diif]

Re: LG 37LG10-UM has grey screen color and ghosting

Yes i'd change it.
Sometimes there are thermal pads on top of some of the ICs on the tcon which then touch the metal shield that covers them. If these aren't replaced the tcon fails again quite quickly.

[ReeceyBurger123]

Re: LG 37LG10-UM has grey screen color and ghosting

Run set for 5 mins.

Bung finger on AS-15.

If it burns--Change it! (AS-15, Not finger....)

+1 how much is a new finger though

[kc8adu]

Re: LG 37LG10-UM has grey screen color and ghosting

as15 definitely.

[steviewonder]

Re: LG 37LG10-UM has grey screen color and ghosting

Aye,those chips are crap,and heat destroys them.Be quick fitting the new one,doing just a few pins at a time,to avoid destroying the new one.A far superior pin-4-pin replacement is the RM5101

[Alastair E]

Re: LG 37LG10-UM has grey screen color and ghosting

I dunno, IME the AS-15 aint bad, easily getting to 20-30,000 hours...
--What more do you want!

Keep heat to a minimum when replacing. I hold 'em down with Mk-2 finger while soldering, it gets warm, I stop let it cool a while before going on.

(Mk-1 finger is too burned from bloody AS-15's!)

[ReeceyBurger123]

Re: LG 37LG10-UM has grey screen color and ghosting

AS15's are odd, Ive seen some fail after 5000 hours and our main living room Samsung has over 20000 hours use plus 3000 more after I fixed it and reset and the As15 is chugging along nicely still same panel as well but the inverter failed I recapped the psu fully as well. Hit or miss with them.

[Alastair E]

Re: LG 37LG10-UM has grey screen color and ghosting

Strange chips--They Really Hate heat when fitting. Ive only ever damaged one that I know got a bit hot when I fitted it.

Dunno what the failure mode is during soldering, as it certainly wasn't too hot, but since I now keep them less than warm when fitting, Ive never had any problems, and went through a phase of doing 3 or 4 a day a little while ago...