NEC LCD1970NX vertical 2" line on screen

[mikejtt]

I have an old NEC Multisync LCD1970NX that has screen problems and not quite sure the cause.. Has anyone experienced these issues and attemped a repair on this one ?

- Monitor runs fine at 1st then after 20-30 mins there will be a small black vertical line that appears on screen (3-5 pixels wide). This line may seem fuzzy with multicolors in it.
- After an additional 5 mins (25-35 mins total) the vertial line widens up and ends up as 1"-2" wide band on screen. It is colored black at first then alternates to black / white band over time.

If I leave the monotor on the vertical line may disappear occasionally and leave fuzzy text on screen in that 2" region & then revert back to the black or white 2" vertical bar on screen.

I have not tried to open up monitor and troubleshoot this one yet but thought I would ask if anyone else has had similar experiences.

Thanks for any help
-Mike

[retiredcaps]

Re: NEC LCD1970NX vertical 2" line on screen

I have not tried to open up monitor and troubleshoot this one yet but thought I would ask if anyone else has had similar experiences.

I suggest opening it up and looking for bad caps and/or poor solder joints. Look for discoloration on the PCB where something may be very hot while running.

[senndogg]

Re: NEC LCD1970NX vertical 2" line on screen

hello. i am reviving this old thread because i have the same problem here.
it is an "old" Nec Multisync lcd1970NX with Lg panel. googled around (because yesterday Badcaps.net wouldnt work for me) and saw other people with the exact problem. i have lot of pics, but you can also see a video on tube posted by a nec victim : http://www.youtube.com/watch?v=666WwTYU8xU

a strange fact (maybe not important) is that when connected to the D-Sub the picture is offset (first and second pic). meanwhile in DVI connection it's centered (third pic).

the boards are full of nichicons and panasonics, and all seem ok. measured some voltages in the t-con. any other idea?

[Jasgriff]

Re: NEC LCD1970NX vertical 2" line on screen

Does look like a t-con issue. Have you disconnected the ribbons cleaned and re attached?

[senndogg]

Re: NEC LCD1970NX vertical 2" line on screen

yes, even checked every pin from the main board to the t-con. but now sth weird happened. the display is all black, doesnt show anything. measured again, there is 12V and 3.3V in the t-con but no 15 and 20V anymore. i did nothing except reseating the lvds.

[Jasgriff]

Re: NEC LCD1970NX vertical 2" line on screen

Very Strange....

You need to trace where the 15v and 20v comes from and see if it is still supplying the T-con or if its failed before it gets there.

There are no fuses on the board that I can see is there?

[senndogg]

Re: NEC LCD1970NX vertical 2" line on screen

ok, lets go further. new voltages:

[selldoor]

Re: NEC LCD1970NX vertical 2" line on screen

Reseat the lvds again - upside down? - it has been known.

[senndogg]

Re: NEC LCD1970NX vertical 2" line on screen

i am sorry selldoor but i didnt understand your question. what do you mean, if i mistakely put it upside down? i double-checked and the connection is ok. in beep mode i checked with my dmm every single connection between the t-con and main board and there is no fault, even when pressing and depressing the lvds. i think the problem is in the little circuit which i have measured the voltages.

[selldoor]

Re: NEC LCD1970NX vertical 2" line on screen

Sorry - badly worded - Yes I did mean had you got it upside down. I know it
sounds unlikely but it has been known to happen.

What did you use for ground when doing the test. Possibly try checking voltage
regulators and get the part numbers and data sheets to see if they are working
correctly.

[senndogg]

Re: NEC LCD1970NX vertical 2" line on screen

thank you selldoor.
a quick résumé of the situation:

the NEC which came to my computer service store yesterday had vertical lines all over the left half.
this problem was very common among this party of NEC monitors, feedback all over the web. but no-one had ever succeeded in repairing it. next day saw this thread and thought about troubleshooting this case.
after playing with the lvds with my dmm, the monitor failed to show the erratic display any more. after re-measuring, the voltages werent all right.
i am very confident with myself that i havent shorted anything in the t-con during testing. lets call this mini-circuit a tcon-psu.
did i really screw it?
or, it was in its last hours and just died in my hands?
are the voltages 20V and 15V correct for a t-con?
if not, could they be responsible for the vertical lines, the original problem?
if yes, i really should repair this mini-psu inside this t-con.
if not, i should give up and the NEC vertical lines issue will remain a mystery.
thank you for your patience.

[senndogg]

Re: NEC LCD1970NX vertical 2" line on screen

i used the ground in the t-con. anyway it was the same as the ground in the main board.

[mikejtt]

Re: NEC LCD1970NX vertical 2" line on screen

I have recently got another LCD1970NX that appears to be operating correctly. I then swapped the power supply from the good monitor to the one that had the lines..
PSU details..
PART NUMBER : 4H.B0170.001 VERSION : 1A ( 1 DC cable op version)
OTHER NUMBER : Other # : BK0001700105, J81000392, LCD1970NX-USB
The monitor would show a black line for 2 sec then disappear and the monitor operated correctly for hours. If I put the flakey psu into the other 'good' monitor with control panel in 5-10 mins this monitor shows a 2" wide vertical yellow bar on the screen.

There is something wrong with the PSU it appears and not the IO board in these units.