HansG HH251 - What's this thing?

[howlerleeches]

My monitor will work for about 10 minutes, then flicker and the backlight will go out. Sometimes, this particular component will make a very high pitched buzzing sound. I'm not really familiar with these kinds of things. What is this, exactly? Sorry for the atrocious image quality.

[t.j.]

can ya get a clearer pic? has copper coil wrap?

[jetadm123]

It appears to be a inverter transformer. And yes, a clearer photo would help. Also, please provide overhead photos, top and bottom, of the entire power board.

[Th3_uN1Qu3]

It definitely looks like an inverter transformer. And yes, if it is bad, the backlights will go out.

[howlerleeches]

Sorry for being so short in my first post, but I was in a rush to get it on here before I had to leave for work.

The only thing I've got to take pictures with is my phone, but I've taken a few more. Hopefully they help. Third picture shows the power board with the bad part in the upper left corner. Fourth is the back side, with the inverter transformer removed, and the solder points in the upper right.

Also, there are two lines of numbers printed on the inverter transformer:
784403
61 0912 80 4 H

Is this something I can pick up at the local electronics store?

Thanks for the replies, guys.

[howlerleeches]

I feel I should add that the monitor (backlight - I can see the image if I shine a light through the back of the actual LCD panel) will only turn back on for about 2-3 seconds after it quits the first time. If I let the monitor sit unplugged for a while, it's good for another 10-15 minutes.

[Rtech]

Can you obtain,a used pair of Backlights, from a friend, another Monitor, a recycle centre, where a monitor may have been ditched, with a broken screen etc ???And also you need to measure the resistance of both transformers for comparison purposes.I suggest that keeping the same orientation on both you mark each pin with a number and then measure as follows...1-2,1-3,1-4 etc,,the 2-3,2-4 etc, then 3-4 etc etc then advise what readings you get.

[Rtech]

Have just returned after a morning run,trying to get fitter, after having a Hip replacement last Xmas, I was giving your problem some thought,and there is an easier way to confirm if the Transformer is faulty.
Swap over the transformers,and see if the Buzzing etc comes from the same transformer as before,OR the same position,ie the changed transformer.I suspect that it is more than possible that the noise is actually coming from the top set of Backlights,due,probably to bad wiring or poor solder joints or the Lamps themselves.

[selldoor]

Hi
A couple of things.

"Is this something I can pick up at the local electronics store?"

No - lcdparts.net, ebay and taobao (Chinese ebay) are the usual sources.

My monitor will work for about 10 minutes, then flicker and the backlight will go out.
If I let the monitor sit unplugged for a while, it's good for another 10-15 minutes.


These are not a usual signs of a faulty transformer, it would not normally come on -sounds more like faulty ccfl or the wiring.

It could also be a cold solder joint or a bad cap - one in the top right
in your picture has an odd shading - one segment of the top of it is reflecting the light ( but it may just be the picture)

May as well do the resistance checks on the transformers as it is easy
Set your meter on 2000 ohms and check as Rtech says.

Looks like its a standard layout so the secondaries are likely to be S1>S2
and S3>S4 in the attached.

Not sure if Rtech means swap the actual transformers over - sometimes just swapping the leads to the lamps produces a different result.

[howlerleeches]

Originally Posted by selldoor

It could also be a cold solder joint or a bad cap - one in the top right
in your picture has an odd shading - one segment of the top of it is reflecting the light ( but it may just be the picture)

I believe you're just seeing a blue marker mark that's on the top of all the caps on this board. As far as I can tell with my limited knowledge and experience, the caps LOOK fine, in that I see none that are obviously bloated.

I'll try my multimeter once I find it.

[selldoor]

I'll try my multimeter once I find it.

Perhaps get a new battery for it if not used for a while?

[Rtech]

Not sure if Rtech means swap the actual transformers over - sometimes just swapping the leads to the lamps produces a different result.

Unfortunately the leads are usually not long enough to swap over,thats why I advised Swap the transformers over...this is the simplest and easiest way to determine if the fault is the transformer or Backlight, and to do any other tests etc would seem to be a waste of time, until he does this.

[howlerleeches]

I got no readings on any other combinations. I'm probably not doing this right.

[selldoor]

That is ok its an oddball type - what do you get measuring the same pins on the other
transformer.

[howlerleeches]

Do I need to remove it to test it, or can it be done while in the board? I had already pulled the other before starting this thread, thinking I'd be replacing it.

I did put the first transformer back in and swap the wires around, as suggested, and the display stays on! For nearly a half hour, now, anyway. The display is quite dim, though, and the brightness will not adjust.

[selldoor]

You can do the resistance test on the transformers with them soldered in.

[howlerleeches]

The second transformer read the same, but I think I killed the monitor. I wasn't very careful on the last test and shorted it. Not sure what's burnt out now.

[selldoor]

It should not be switched on to do resistance tests!.
If it was its probably your meter that has gone - try testing a few low voltage things
with it and on ohms touching the probes together. Hopefully it has a fuse that has just blown.

[selldoor]

If your meter is ok - with the power off test the fuse on the power board. Black one just behind the mains socket. Should test 1 ohm or less same as touching the probes together

[howlerleeches]

Maybe it's the fuse on the power board that blew, then. I will check it out. Definitely had the monitor unplugged when testing with the multimeter. I didn't have the power board secured when I was doing a test run with the backlight wires switched, and it moved and shorted against the body as I was turning it off. Just really dumb on my part.