Westinghouse lcm-19v1 sl 2 Seconds to Black

[gregory121295]

So, I have a monitor that I've had for a couple months. I used it for about a week a month ago. It started out with the back-light working but the monitor needing to be hard reset until the back-light would stay on. After the back-light was on for a couple minutes, sometimes it would turn off later, sometimes it wouldn't.

I didn't think anything of it until one day, after about a week, it finally just turned off. I know it's the backlight, as the panel works just fine.

What the odd thing is, though, is that the only non surface mount capacitors on this board are on the control board, not the inverter board, and they're aluminum caps, not electrolytic.

Here's a picture of the top of the inverter board.

[retiredcaps]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Here's a picture of the top of the inverter board.

Is this a picture of your actual board or a stock photo?

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Right now, I don't have access to a camera, so It's a stock photo. I'll add actual pics sometime soon.

[jetadm123]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Where are the connectors for the ccfl's? Underneath the board?

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

yes. Underneath the board, there are two black plugs, spaced about 2 inches apart. Each plug has two slightly separate sections of four holes.

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

You need to measure the resistance of the secondary winding on the inverter tfmrs,From the photo there is probably 2 pins at the top end(nearest the edge of the Board) of each tfmr.Measure each and advise.

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Ok. Here's a diagram of the transformers, with measurements of the secondary windings. I can also measure the primary windings if need be.

Xfmr 1:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.4 ohms

Xfmr 2:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.4 ohms

Xfmr 3:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.4 ohms

Xfmr 4:
x + y = 0.4 ohms
x + z = 0.4 ohms
y + z = 0.5 ohms

EDIT:
I should add that the back-light flickers on for about a second when I turn on the monitor, although only half of the bulbs turn on, and they don't look like they're on at full power.

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

0.4 ohms is not a secondary measurement,you are looking for something between 550-1200 ohms.A photo of the bottom of the Board would probably help.

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Here's a pic of both the top and bottom of the actual board. Sorry for the quality, I'll upload better photos soon.

[jetadm123]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

I believe the 8-pin devices,U1-U4?, are mosfets used to drive the inverter transformers. Check them for shorts. Look up the datasheet for these devices. With your meter set to 200 ohms, measure:

G--->D
G--->S
D--->S

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Yes, it turns out they are mosfets. U2, however, is 20 pins, and I can't find the datasheet for it. Should I test both channels, and how so? I can't seem to get a reading at all with my multimeter set to 200 ohms and my negative lead in com. The meter just says 1, as if nothing is connected.

Here's a schematic of the mosfet, TPC8401.


EDIT:
Rtech, did I test the right pins? Which pins are the secondary windings? Should my negative lead be in com or 10adc? I figured com, but I get a much higher reading when the lead is in 10adc.

[retiredcaps]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

1) This tutorial will help you understand some of the readings.

http://www.sparkfun.com/tutorials/202

2) My fellow Canadian has a 5 minute multimeter tutorial

http://www.youtube.com/watch?v=bF3OyQ3HwfU

3) Plus I have multimeter section starting with post #19

https://www.badcaps.net/forum/showthread.php?t=10419

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Its not possible to identify the secondarys from the photos unfortunately,ALSO where do your lamps plug into ??there seems to be no connection for them on the board.Measuring resistance the Black(negative lead) goes to common on the meter.I assume you are taking measurements with the board disconnected and no power on ??

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Now that I have a cup of coffee,you are going to have to measure,the resistance as follows;-
Black lead to 'x',measure to every other pin.
Black lead to 'y', measure to every other pin.
Black lead to 'z', measure to every other pin.
Note down all the results and compare them, they should be very very close for every transformer,if not then you will have to investigate from there.

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Rtech, the lamps plug into the black plugs on the bottom of the board, as shown in this photo.

yes, I have neg in com and am taking measurements with the circuit off.

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Well you learn constantly the Black plugs, I never even considered as plugs, what does the bit on the end of the Lamp cable look like ??first time I have seen these !!! Lets know what the tfmrs read.

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Here's pics of how the lights plug in. Working on readings from the xfmrs now.

Edit:
Here are the Xfmr readings. I'm getting a lot of no readings though. Any idea why?

Xfmr 1:
x+a= 610 ohms
x+b= no reading? (stays on "1" even if I go up to 2000k)
x+c= no reading?
x+d= no reading?
X+e= no reading?
x+f= no reading?
x+g= no reading?

y+a= 610 ohms
y+b= no reading?
y+c= no reading?
y+d= no reading?
y+e= no reading?
y+f= no reading?
y+g= no reading?

z+a= 610 ohms
z+b= no reading?
z+c= no reading?
z+d= no reading?
z+e= no reading?
z+f= no reading?
z+g= no reading?

__________________________________________________ ______

Xfmr 2:
x+a= 607 ohms
z+b= no reading?
z+c= no reading?
z+d= no reading?
z+e= no reading?
z+f= no reading?
x+g= no reading?

y+a= 607 ohms
y+b= no reading?
y+c= no reading?
y+d= no reading?
y+e= no reading?
y+f= no reading?
y+g= no reading?

z+a= 607 ohms
z+b= no reading?
z+c= no reading?
z+d= no reading?
z+e= no reading?
z+f= no reading?
z+g= no reading?

__________________________________________________ ______

Xfmr 3:
x+a= 629 ohms
x+b= no reading?
x+c= no reading?
x+d= no reading?
X+e= no reading?
x+f= no reading?
x+g= no reading?

y+a= 629 ohms
y+b= no reading?
y+c= no reading?
y+d= no reading?
y+e= no reading?
y+f= no reading?
y+g= no reading?

z+a= 629 ohms
z+b= no reading?
z+c= no reading?
z+d= no reading?
z+e= no reading?
z+f= no reading?
z+g= no reading?

__________________________________________________ ______

Xfmr 4:
x+a= 606 ohms
x+b= no reading?
x+c= no reading?
x+d= no reading?
X+e= no reading?
x+f= no reading?
x+g= no reading?

y+a= 606 ohms
y+b= no reading?
y+c= no reading?
y+d= no reading?
y+e= no reading?
y+f= no reading?
y+g= no reading?

z+a= 606 ohms
z+b= no reading?
z+c= no reading?
z+d= no reading?
z+e= no reading?
z+f= no reading?
z+g= no reading?

[Rtech]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

All we were trying to do was identify the secondarys, and you have done that,worry not about the rest.Transformer 3 looks a little high !! Normally members work to the 3% rule,ie if there is more than a 3% difference in the secondary resistance, then its likely that the transformer may well be faulty, so 3 would look marginal ,and MAYBE the problem.I see Qty 6 'U' shaped lamps, have no idea how they connect together,or even if they do,as I have never seen this set up, so hopefully someone has who will leap in and advise us both,a quick glance would assume that only 2 actually light ,do you see anything from the lamps when you try to start the Monitor and associated PC Signal ??
Also there is a 4 0r 8 pin connector on the edge of the Board ,is there anything written on the board,OR the one it plugs into to indicate what voltage/Function etc each of the pins have??

[budm]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

Can I see closed up pictures of the left side of the lamp assembly? I want to see how the end of the lamps are connected.
And by the way, none of the lamps flash for a second?

[gregory121295]

Re: Westinghouse lcm-19v1 sl 2 Seconds to Black

When I start the monitor, only RIGHT after i plug in the power to the wall the lamps kind of flicker on for a second or two. Rather than explain it, here's a video of it.
http://youtu.be/Bnc4FkGyy2w

EDIT: I managed to remove the light assembly. here's a picture of both sides of the circuit board.