Acer H243H Bbmid - replacing caps not enough

[mcflash]

Hello,

I am from Germany, so I am sorry for my bad english.

I have here a Acer H243H Bbmid.

2 seconds to black. you can see the picture with a flashlight.
I replaced the caps on the supply board. It still doesn't work.
I left it for a few weeks. on a new test it worked with a whisteling tone.
I opened it again and then there was the 2 seconds to black again with that whistling tone. I got near with my ear and could locate the tone on the "red marked" piece.
before the monitor shuts off it is flickering as the whisteling tone is.
what can I do next to find out what is wrong?
Is it possible that the whisteling piece is broken or can it be another part which causes in the marked piece the failure?

[Rtech]

Re: Acer H243H Bbmid - replacing caps not enough

It could be the bottom set of backlights that is causing the problem.You need to measure the resistance of the two transformer secondaries, and compare them !!

[mcflash]

Re: Acer H243H Bbmid - replacing caps not enough

I have red the tutorial, but I 'm not sure.

Shall i measure like I marked in the photo?
put GND on one pin (black) and measure the others (red)?
how do i set my multi meter 200 ohm or 2k ohm.

thank you

[budm]

Re: Acer H243H Bbmid - replacing caps not enough

@mc, the high voltage winding is on the two pins on the opposite side of your marking, your marking is for the primary side winding of the transformer.

[mcflash]

Re: Acer H243H Bbmid - replacing caps not enough

okay,
but how can I measure the transformer.
Where put the GND? on the side with my marking? so I can measure from primary to secondary winding. or only secondary winding?
this is what I did not understand properly.

[budm]

Re: Acer H243H Bbmid - replacing caps not enough

See picture. Just measure at the two pins of HV Winding which is on the secondary side as shown.

[mcflash]

Re: Acer H243H Bbmid - replacing caps not enough

Thanks for the help.

I measured the HV winding on secondary side.

transformer 1: 647 ohm

transformer 2: 658 ohm

transformer 1 is the one which made the noise.

so they should be in the 3% tolerance if I understood it right in the guide thread.

[Rtech]

Re: Acer H243H Bbmid - replacing caps not enough

That looks good, suspect the backlight and/or its wiring

[mcflash]

Re: Acer H243H Bbmid - replacing caps not enough

hello
I disassembled the panel.

and the bottom pair looks like this. I think it is not good.

I have another samsung 19" monitor.

can I try the backlight from this one or must it be another 24" backlight? have the manufactures different voltages or are they all the same and the just get more current?

[Rtech]

Re: Acer H243H Bbmid - replacing caps not enough

You can try the 19" one for Test ONLY,as if you try and fit it to use permanently, you will get a large shadow on the Screen.So its either buy new,or an old 24" from somewhere with a set of good lamps.

[On-3]

Re: Acer H243H Bbmid - replacing caps not enough

hello
I disassembled the panel.

and the bottom pair looks like this. I think it is not good.

I have another samsung 19" monitor.

can I try the backlight from this one or must it be another 24" backlight? have the manufactures different voltages or are they all the same and the just get more current?

how difficult was it to remove the back light and did you find anywhere selling them? I'm having the exact same problem as you.

[OBTA13]

Re: Acer H243H Bbmid - replacing caps not enough

Here's a link to my youtube showing the symptoms
I already opened up the power board and visually inspected the caps and none were bulging. Should I just replace the caps first or can this be a backlight issue itself?


https://youtu.be/wF0w2yKxIsc

[hitec]

Re: Acer H243H Bbmid - replacing caps not enough

check fluorescent lamp