Samsung Syncmaster 940BF

[xylopagus]

This has been my daily monitor for over 3 years. Now, when I turn the monitor on it makes a buzzing sound. Sometimes if I turn it off and then back on again, I get an image for a second or two. There are no obviously blown caps, but that doesn't really mean much.

Thanks!

[retiredcaps]

Re: Samsung Syncmaster 940BF

Now, when I turn the monitor on it makes a buzzing sound. Sometimes if I turn it off and then back on again, I get an image for a second or two.

We need a picture of the entire board. Your pics are chopped off. Use this guide as a start and then post your questions here. Start with post #13 and #14.

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

[xylopagus]

Re: Samsung Syncmaster 940BF

So, I've looked through the walk through/guide and all I've come up with is that I am, indeed, a "2 seconds to black" case. I can't seem to get any normal readings from my multimeter (it's old? I'm not sure how I could be so completely wrong that nothing comes out correctly).

Replaced the four similar caps with caps from a local parts store and the situation is the same (although my soldering job is absolutely terrible). I power it on and I hear sporadic buzzing for a bit and it looks like the screen is flickering at the same frequency as the buzzing. When the buzzing stops, I lose the image, but if I shine a flashlight directly at the screen I can still see it.

Here are some updated pictures.

[retiredcaps]

Re: Samsung Syncmaster 940BF

I can't seem to get any normal readings from my multimeter (it's old? I'm not sure how I could be so completely wrong that nothing comes out correctly).

Replaced the four similar caps with caps from a local parts store and the situation is the same (although my soldering job is absolutely terrible).

1) Put your multimeter on 200 ohms (if manual ranging). Touch the 2 probes together. What reading do you get?

2) Please list all the multimeter readings from the inverter transformers (using 2000 ohms setting this time) and we will intrepret them.

3) What caps did you get from the local store? What brand and "series"?

4) BTW, a poor soldering job can also cause 2 seconds to black. Wiggle the caps and see if they are loose or not.

edit: 5) PS. Try to get a 2000x2000 resolution for photos. This will give us better detail.

[jetadm123]

Re: Samsung Syncmaster 940BF

The flickering sounds like a cap problem. Once you have verified retiredcaps request for the cap brand/series, one question: why did you replace only 4 caps? And did you use the exact same capacitance value? There are at least 2 (possibly 3) other caps you should have replaced. One is to the left of the inverter transformers. The other 1 or 2 are small startup caps and are probably hidden underneath the white glue (can't tell from your photo). The large one can generally be left alone unless it's showing some signs of leakage.

[sabre504]

Re: Samsung Syncmaster 940BF

All the large caps that i have found to be faulty in the past (not many)

Have had leaks from the legs rather than bulging tops worth a look

[iro]

Re: Samsung Syncmaster 940BF

Hello i have same monitor with leaking caps. Problem is that i cannot get 820uF 25v ones.
Can i use any oter?

[retiredcaps]

Re: Samsung Syncmaster 940BF

Problem is that i cannot get 820uF 25v ones.
Can i use any oter?

1000uF 25V low ESR caps will work as long as it fits height and diameter wise.

[iro]

Re: Samsung Syncmaster 940BF

Thx.

[bmajda]

Re: Samsung Syncmaster 940BF

Hello,

I have new qustions regarding this subject.
Monitor loses light after five seconds.
On this power supply all electrolytic capacitors are OK, but I have doubts about SMD capacitor that is placed downside on board position C230.
I measured it and it is 0,8 uF, but I don`t know what the value should be.
Did anyone encounter this problem.