Westinghouse LCM-20v5

[vehf277]

I have LCD monitor Westinghouse LCM-20v5, inverter/power supply DAC-12M030B Rev1F. If it starts to work from cold condition it waits about 1 sec to show normal image. Then it works fine about half an hour, then it becomes blank. Turn off/turn on – goes to "2 seconds to black" condition. I think that it's a backlight issue because when I use flashlight, there is badly visible image on screen. First of all I resoldered all joints excluding on-surface components. Then I changed 6 capacitors for new ones (I found it by googling “Westinghouse LCM-20v5”). No changes.
Then I tried to cool DAC by small fan. In this case monitor worked without "2 seconds to black", as long as I needed.
Does anybody know a link to DAC-12M030B schematic or circuit or wire diagram and any suggestions, please?

[PlainBill]

Re: Westinghouse LCM-20v5

the compsotion of the pictures is excellent. It shows the relationship of the various boards and connectors, and gives some interesting information. This appears to be a slightly unusual design. Usually we see output and return lines for each CCFL coming to the same connector. This design appears to use two sets of connectors. Not a big deal.

The size of the pictures leaves a little to be desired. This board can support up to 2000 x 2000 pixel resolution, and we will need every bit of it for the next picture. I need a picture of the back of the power supply / inverter. The hint that this might be temperature related is significant.

Also, you have indicated you have replaced the capacitors. What caps (brand and series) did you use?

PlainBill

[kbrletic]

Re: Westinghouse LCM-20v5

If you have hot air station, you could warm element by element until you come to a bad one.

[jetadm123]

Re: Westinghouse LCM-20v5

Welcome to the forum! My initial reaction is that you have an overheating problem. Good troubleshooting with the fan. If the caps that PlainBill asked about are of good quality, then you may have a component that's starting to fail because of the heat. Or, you may have a bad solder joint. As the the board heats up, thermal expansion may cause the solder to separate from the pad or the device lead. The devices that generate the most heat are the heatsinked devices, bridge rectifier, inverter transformers and the 4 8-pin driver chips next to the inverter transformers. Try resoldering the pins/leads of the devices mentioned. Of course, some of the surrounding devices could also be affected by the heat. And there's always the possible lousy soldering job that was done at the factory and it's just starting to show up now.

[alexanna]

Re: Westinghouse LCM-20v5

Yes the power and return connectors are on different sides of the board.
In the third picture there is a resistor by the ADJ pin on the connector that goes to the logic board, look at it closely for any sign of overheating or poor solder joints.
Al.

[vehf277]

Re: Westinghouse LCM-20v5

I have LCD monitor Westinghouse LCM-20v5, inverter/power supply DAC-12M030B Rev. 1F. If it starts to work from cold condition it waits about 1 sec to show normal image. Then it works fine about half an hour, then it becomes blank. Turn off/turn on – goes to "2 seconds to black" condition. I think that it’s a backlight issue because when I use flashlight, there is badly visible image on screen. First of all I resoldered all joints excluding on-surface components. Then I changed 6 capacitors for new ones (I found it by googling “Westinghouse LCM-20v5”). No changes.
Then I tried to cool DAC by small fan. In this case monitor worked without "2 seconds to black", as long as I needed.
Does anybody know a link to DAC-12M030B schematic or circuit or wire diagram and any suggestions, please?

Resending picts 2000x1500 plus back side of inverter plus capacitors (similar, not same ). EVERY JOINT EXCLUDING ON-SURFACE COMPONENTS WERE RESOLDERED carefully, I have a small experience in soldering

Please to everybody: this DAC is used by a lot of brands in particular by Acer AL1916Wc-1 LCD monitor, I have the service manual for it and can upload it for everybody (don't now how to, give me an advice how, I'm newbie )
This manual has a circuit diagram but in my opinion not a diagram of said DAC, but of a second PCB so, please, I need a circuit diagram of DAC-12M030B Rev. 1F. In addition, as you can see, this DAC uses chip OZ964GN which is well known by experienced people but not by me, I'm really newbie in particular LCD monitor repairing issues

[jetadm123]

Re: Westinghouse LCM-20v5

Resending picts 2000x1500 plus back side of inverter plus capacitors (similar, not same ). EVERY JOINT EXCLUDING ON-SURFACE COMPONENTS WERE RESOLDERED carefully, I have a small experience in soldering

Please to everybody: this DAC is used by a lot of brands in particular by Acer AL1916Wc-1 LCD monitor, I have the service manual for it and can upload it for everybody (don't now how to, give me an advice how, I'm newbie )
This manual has a circuit diagram but in my opinion not a diagram of said DAC, but of a second PCB so, please, I need a circuit diagram of DAC-12M030B Rev. 1F. In addition, as you can see, this DAC uses chip OZ964GN which is well known by experienced people but not by me, I'm really newbie in particular LCD monitor repairing issues

PlainBill supplied a link in post #2 on how to post documents. It's very well written with photos. Since you're able to upload photos, there's really no difference. Here it is again:

https://www.badcaps.net/forum/showthread.php?t=1868


Power supply schematics for the Delta "DAC" series are some of the most difficult to find.

[jetadm123]

Re: Westinghouse LCM-20v5

Since you're getting up to half an hour of operation before "2 sec to black", try accelerating the shutdown process by using a blowdryer set to the high heat setting and heat the various components to see if you can trigger the shutdown process.

[alexanna]

Re: Westinghouse LCM-20v5

Your problem sounds like it could be a very time consuming process.
Any time you apply cooling to the board it is affecting everything on the board even if it's not directed to it, Air flow could make a difference.
Sometimes when you diagnose something, you have to know what's good before you can find what's wrong.
I have found it easiest to try to verify what voltages are good.
If I understand you correctly you are losing back lights but you still have an image visible?
If it were me I would start by verifying the inverter voltage is good, And also checking to see if the back light on voltage stays the same as the back lights go off.
In the past I have soldered a small wires to the BL on pin of the back light controller , and to a point that has voltage for the inverter,[ this allows the DMM to be outside the covered area] , and then covered everything up with the plastic back case and let it warm up,and see if the voltages stay fairly constant when the problem occurs.
This may not tell you what's wrong, but it could direct you to an area that needs further testing
Al.

[vehf277]

Re: Westinghouse LCM-20v5

Thank you VERY MUCH, all of you for your attention and patience! I will use all of your advices and if I will find something interesting I of course will post it. I uploaded manual for said Acer AL1916Wc-1 LCD monitor. It's my small gift for all of you

[vehf277]

Re: Westinghouse LCM-20v5

I found a Chinese site where is a lot of DELTA schematics, http://www.wjel.net, it is a Chinese forum so I MUST be registered there but I don't know Chinese Maybe somebody knows how to get registered there as English-speaking person. Also possibly there is a SIMILAR schematic(s) in this forum or anywhere else: two groups of lamps, two transformers, four mosfet chips, OZ964GN chip?

[Eric_R]

Re: Westinghouse LCM-20v5

I have two westinghouse 20v5's which had the 2second to black problem initially after 14-16 months of use. In that case I upgraded all the switching filter capacitors on the power supply board with oversize hi-rel ones if I could get them to fit standing up or lying down. I did this a year ago and they both still work. The only one I didn't replace was the 150uf 400volt one. Looking at the small size of caps your using to replace the old ones, you might still have a problem if the replacement cap is marginal and starts heating up where the ripple voltage causes the power good signal on the power supply board to fall outside the normal limits and shut the supply down again. I have a list of cap parts I ordered from digi-key that I used to replace all the caps on my PS board if you think you cant find another reason the unit fails during heat-up.