Westinghouse L2610NW 26" 16:10 LCD backlite problems

[rogerk]

I know it needs some caps. Wanted to ask if anyone repaired one before I open and start cutting them free.
Last year (july2011) backlite would go off after 5mins. or so when over 75°. Found all the caps glued down so as not to see their values.
None puffed, all colored Lt.Brown (like old bad panny's)
I made some holes, mounted a CPU fan over the main cap. Worked til today.
Now has the 2 sec. to black and speaker pop. Can read the text w/flashlite.

Westinghouse L2610NW 26" 16:10 LCD Monitor UPC No: 882777052402
Made by
CHIMEI INNOLUX CORP STSP BRANCH
3 SEC 1 HUANSHI RD
SOUTHERN TAIWAN SCIENCE PARK
TAINAN HSIEN, 741 TAIWAN

Main pcb; APD logo = Asian Power devices inc. model FM-140A12

There are 26" TV tuner versions; 26H730, VR2680 ect. but are Aspect Ratio: 16:9 Might use same PCB.
Thanks in advance. I will document repairs.
Roger
A side note; Son's old Viewsonic VX1962WM only needed 2- 220mf @35v. caps. C101 and C302 so I have a working monitor.

[momaka]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

I know it needs some caps. Wanted to ask if anyone repaired one before I open and start cutting them free.
Last year (july2011) backlite would go off after 5mins. or so when over 75°. Found all the caps glued down so as not to see their values.
None puffed, all colored Lt.Brown (like old bad panny's)

It's interesting to this thread pop up this week. Last week I got the same monitor (Westinghouse L2610NW) on Craigslist for $10. It was advertised as not working, but when I got it home it worked fine. I should note, however, that there was quite a bit of buzzing coming from the inverter. It went away only after I turned the brightness up to and above 90%.
Therefore, I tore it open regardless just to see if there is anything obvious.

Mine had brown caps as well - they were all United Chemicon KY series. Those are extremely reliable. If your caps are the same, then I don't think new caps will help it. (Or maybe they will? I don't know for sure since I didn't replace mine either.)

Personally, I think it's the inverter design that's causing this. For those interested, the inverter uses 6 HV inverter transformers and there are 12 CCFL tubes. The CCFL tubes are grouped in sets of 2 and each set is wired in series to the HV output of each inverter transformer (i.e. 2 CCFL tubes per HV transformer). The circuit that drives these transformers is a single circuit comprising of 4 MOSFETs arranged in full-bridge (the inverter transformers primaries are wired in parallel to the output of the 4 MOSFETs). Now this is a very good design in terms of reliability, but it's too simple and (at least from what I understand) if any of the CCFL tubes or HV transformers becomes bad or degraded due to age, it can throw off the whole inverter. And with that many CCFL tubes and transformers, I think some of them are bound to degrade faster than the others. I don't know for sure if this would be the reason for these inverters to go 2-seconds-to-black, but I think it's a plausible theory.

So before replacing the caps, I would say try playing around with the backlight brightness to see if that will bring it operational. Since my monitor was working, I wrote down the menu sequence to turn the brightness up/down. There are 6 buttons on the side of the monitor, with button #1 on top and button #6 (the ON/OFF switch) on the bottom.

To turn the brightness all the way UP:
1) Press button #5 and wait for about 1 to 2 seconds
2) Press button #4
3) Press and hold down button #4 for about 3 to 4 seconds, then release it and wait for another 5 seconds
4) Turn the monitor OFF (press button #6), and then turn it ON.

To turn the brightness all the way DOWN:
1) Press button #5 and wait for about 1 to 2 seconds
2) Press button #4
3) Press and hold down button #3 for about 3 to 4 seconds, then release it and wait for another 5 seconds
4) Turn the monitor OFF (press button #6), and then turn it ON.

Note: the number of seconds above is just approximate and you don't have to be very exact.

Let me know if this works for you.

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Awesome Idea. I will try.
The fan I added really dinna help above 70° room temp.
Thanks
Roger

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

was off sence june.
Now no backlite at all.
I want to fix..

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Tried again tonight.
Can just see video as usual.
Backlite not lite.
Powering on/off via button 6.
Did get some internal speaker pops.
Roger

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

PCB pics added.

[selldoor]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Pictures are poor too much flash. You need to work out what are the secondary windings on the 6 inverter transformers. I cannot find your transformer -They could be as in this
http://www.lcdparts.net/TransformerD...ProductID=4175

or as in this
http://www.lcdparts.net/TransformerD...ProductID=2796

Power off meter on 2000 ohms you need to measure S1>S2 S3 >S4 for each
transformer. and post the results

[budm]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

This form factor transformer may have pin out like this:
http://s807.photobucket.com/albums/y...t=DSC00191.jpg

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

selldoor your links are inop.
Any of my TMS92859CT's ?

Going by budm's pic
pin1 1350 ohm
pin2 .8
pin3 .8
pin4 1340
Xfomers OK ?

[budm]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

All of them read like that?

[momaka]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

This form factor transformer may have pin out like this:
http://s807.photobucket.com/albums/y...t=DSC00191.jpg

And it does.

I uploaded some pictures of when I took mine apart. Just used that monitor last week for an hour or so and it still works, though it was quite loud (lots of buzzing from the inverter).

As I mentioned before, I suspect that the design of this inverter is not the best when the CCFLs and inverter transformers become unevenly worn. I think the only 2 possible solutions are to either replace the CCFLs/inverter transformers or tweak/fiddle with the feedback circuit (and maybe disable some of the CCFLs after doing this).

**EDIT**
Just found a note from when I measured the secondary sides on my inverter transformers. Starting with the transformer on the right and continuing left (on that first topside picture):
5.14 KOhm, 5.21 KOhm, 5.13 KOhm, 5.22 KOhm, 5.14 KOhm, 5.13 KOhm

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Thanks for the Pics. Way better than what I took.
Still to repair
Roger

[budm]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

"5.14 KOhm, 5.21 KOhm, 5.13 KOhm, 5.22 KOhm, 5.14 KOhm, 5.13 KOhm" That is big different from rogerk readings.

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Yes, but not sure of pin outs.
I went to like, pin 1 to last acrost top for 1st. Like a IC.
And so on for the other 3.

[budm]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

You did it correctly, I never seen that high (>5K) resistance for 26" TV.
But since all your transformers reading are within 3% from each other, then we need to look somewhere else for the problem, I just hope it is not the lamp problem, but you will need to verify them.

[selldoor]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Can you do a close up of the caps on the inverter board.
With it all connected up can you unplug all but the first lamp lead switch on and see if it flashes. its difficult but try and remember how bright and if it has any colour. Switch off
Unplug that lead and plug in lead 2 Switch on and see if it flashes etc. Switch off.
Repeat for all six and report result. High voltage 1200v so remember to switch off.

[momaka]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

That is big different from rogerk readings.

Yes, I'm surprised too.
To be honest, though, I don't remember how I tested these transformers. I *think* I tested between the 2 HV output pins, but I really do no remember any more. Will need to tear it down to test it again, but that's not exactly something I want to do unless I really have to (I get highly impatient with prying LCD monitors open).

Can you do a close up of the caps on the inverter board.

They are all Chemicon KY on my board. His seem the same too. Overall, this PSU board is built quite well IMO.

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

momaka's ohm reading for any xformer I think is posted wrong.
I was using my old Fluke 23 multimeter.
Which Caps that be? looking for bottom seal expanding?
I will try your lamp idea.
Just so you know, at power up is no CFL backlite.
Thanks

[rogerk]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Just got 6 trade in retired 17" LCD's. With no use for.
Thinking why not use one to test the CCFL's one at a time.
To comfirm if prob is in display or the FM-140A12 PCB.
Any thoughts before begin ?
Thanks

[selldoor]

Re: Westinghouse L2610NW 26" 16:10 LCD backlite problems

Just so you know, at power up is no CFL backlite.
Thanks

You said originally that it was 2 seconds to black are you saying now that it
just doesnt come on at all.