NEC AccuSync LCD 52VM (model L154F0)

[redmike5]

Hi there,

I have recently picked up two NEC AccuSync LCD 52VM (model L154F0) monitors. Both of them have the same problem. When switched on, only a couple of pixel lines on top of the screen show picture. The rest of the screen stays black. This is exactly same for both of these monitors.

I suspect problem with the logic board or the LCD panel itself. I have opened the monitors and checked for obvious faults i.e. bad caps or burned elements, but visually all seems perfectly ok. In case this helps the panels are LG. Philips LM150X08.

So I wonder whether anybody came across this problem before. Is there any simple solution or test I could do to determine the culprit?

I will appreciate any help or suggestions.
I can post pictures of the boards later on if this is going to help.

Cheers,
Redmike

[retiredcaps]

Re: NEC AccuSync LCD 52VM (model L154F0)

I can post pictures of the boards later on if this is going to help.

Clear focused pictures of your boards (using manage attachments and not posted inline) always help.

Check your voltage regulators on the logic board.

[redmike5]

Re: NEC AccuSync LCD 52VM (model L154F0)

Thanks for your reply retiredcaps.
I tried to take some pics of the boards, but the quality is questionable.
Please let me know whether these will do, or do I have to try harder.

I am going to check the regulators, but since I am a rookie, I thought I clarify the methodology first.

So I assume the voltage regulators are the three 8 pinned smcs? I am going to assemble the boards back and power the monitor up. Then I am going to measure the voltages on each pin respective to ground? Does this sound correct? Please let me know.

Thanks,
redmike

[retiredcaps]

Re: NEC AccuSync LCD 52VM (model L154F0)

So I assume the voltage regulators are the three 8 pinned smcs? I am going to assemble the boards back and power the monitor up. Then I am going to measure the voltages on each pin respective to ground? Does this sound correct?

U601 and U602 are your voltage regulators. Yes, measure each pin with respect to ground (I typically use a ground screw closest to what I'm measuring).

The voltage regulators might have part numbers like AS1117-33 where the suffix represents the output voltage (3.3DC V).

Report all voltages.

[redmike5]

Re: NEC AccuSync LCD 52VM (model L154F0)

The voltage regulators might have part numbers like AS1117-33 where the suffix represents the output voltage (3.3DC V).

Report all voltages.

Thanks retiredcaps. The voltage regulators were indeed 3.3V and 1.8V.
However, I managed to get a get a loan of another monitor with similar LCD panel (LM150X06). I have swapped the panels and.....the NEC works perfect with the swapped panel. To the contrary, the other monitor with the NEC panel behaves oddly. I say oddly as there is picture on the screen, but it looks like every second pixel is black and dead and the picture does not refresh, i.e. whatever the scereen shows just after the monitor powers up stays on it forever. I wonder if this was due to the fact that NEC uses 14connector wire from the logic board going to the 20connector plug at the panel, but the other monitor uses 20connector wire?

Anyway, it looks to me that it is the pannel that had it. Surprasingly enough I have two of them with the same fault.

Is there any point trying to look at the elctronics in the bad panel? Are these fixable? Does anyone have any experince with this?
Thanks,
Redmike

[retiredcaps]

Re: NEC AccuSync LCD 52VM (model L154F0)

Is there any point trying to look at the elctronics in the bad panel? Are these fixable?

If you haven't already tried, try cleaning and reseating the connector to the panel.

For the components on the panel, you can see if there are any shorted SMD capacitors by using your multimeter. Any reading less than 30 ohms suggests a short.

Some panels will also have a fuse. A good fuse should read less than 1.0 ohms.