Another Samsung Syncmaster 245B - How to get started?

[ipanini]

Hi everyone,

First off, congrats with your terrific forum!
Let me first introduce a little: I'm from Belgium, have fair electrical skills, but only 'some basic' electronic skills.

My situation:
I have just recently acquired a 2nd Syncmaster 245B from ebay with the purpose to use 2 of these 90° rotated in dual view.
Unfortunately the new arrived monitor displays no image at all.
- no image at all
- blue led shows when powered on
- blue led starts to blink when PC goes to sleep
- PC recognizes monitor (both Win 7 and Ubuntu)
- tested on multiple PC's

I've already managed to open up the monitor, and took some photo's.
I'm putting them up on Flickr. I guess that's ok for the forum rules?
http://www.flickr.com/photos/ipanini...7627200465477/

At first sight I see no bulging caps. I've checked 4 fuses, 2 glass type and 2 others following pictures and advice here on the forum.

Now I'd like to start measuring some tensions.

Question:
Is it ok to power the monitor with the backlight and the LCD connector disconnected?

Thanks for your support!

Erwin

[jsog]

Re: Another Samsung Syncmaster 245B - How to get started?

Your pictures are good, but not high enough resolution to read PC board labels. Locals prefer them as forum attachments, hi-res (up to 2000x2000), no flash, straight-on. There are no pictures of the top side of the inverter.

The LED suggests a backlight problem. If you can see an image with a flashlight or bright sunlight, that would verify it.

Caps don't always fail visibly, which is why ESR meters are useful. Check the caps and fuse on the inverter board, left side of picture #5, DSC_0071.

[ipanini]

Re: Another Samsung Syncmaster 245B - How to get started?

Hi,

Thanks for your quick reaction and suggestion.
For information: the photo's on Flickr are available in 3872 x 2592 by clicking on the photo, then in the right hand upper corner - show all sizes, there you can pick the size to your liking. I agree it's not obvious..

I've checked the fuse on the inverter board, it's OK. Also the caps don't show any odities, at least not to my untrained eye. Compared to other pictures I found here on the forum, they look fairly similar. I guess the white stuff at the top of the caps is glue..

I've tried the flashlight before opening up, I could not distinguish anything on the LCD.

Trying to upload some more pictures here, but I seem to get a 'security token' error? Or perhaps I should downsize.. Yes that does it!
I'll resize the others and upload them tomorrow.

Here's a link just in case DSC_0002.jpg and this should be 3872 x 2592

For proper measuring:
Should resistances be unsoldered from one side?
Can voltages be measured with the backlight and the LCD connectors disconnected? Or should all be connected.. ?

Erwin

[jsog]

Re: Another Samsung Syncmaster 245B - How to get started?

While the inverter is out and handy, check the resistance of all of those transformer secondaries, the two pins on each closest to the CCFL connectors. They should all be very close to the same value.

After that, go back to the existing 245BW threads, and check the most likely stuff. Those power resistors are a common problem, and the cap near them looks a little bulged.

[tom66]

Re: Another Samsung Syncmaster 245B - How to get started?

Check the resistance of the three brown coloured power resistors next to the capacitor. All three should read the same; if I remember correctly, about 68 ohms.

[ipanini]

Re: Another Samsung Syncmaster 245B - How to get started?

Here are the other photo's resized to 2000.
Thanks for helping out!

Erwin

[ipanini]

Re: Another Samsung Syncmaster 245B - How to get started?

While the inverter is out and handy, check the resistance of all of those transformer secondaries, the two pins on each closest to the CCFL connectors. They should all be very close to the same value.

Those power resistors are a common problem, and the cap near them looks a little bulged.

I've checked the transformer secondaries, measured directly at the 6 connecors, they all read approx. 580 / 590 Mohms.

Could you be a bit more specific about the 'cap being a little bulged'?

From what I can see, there's a component (don't even know what it is), very small, sitting between the (main) connector and a 16 legged IC, it has white stuff all over - Is this normal?
On the picture from the other thread I linked to previously, I can also see some white stuff... Hence I thought it to be ok...

Thx,

Erwin

[jetadm123]

Re: Another Samsung Syncmaster 245B - How to get started?

A common failure on your model power board are resistors RB805, RB806 and RB807 located in the middle at the top of your board in your photo. They each should read 68 ohms.

[jsog]

Re: Another Samsung Syncmaster 245B - How to get started?

I've checked the transformer secondaries, measured directly at the 6 connecors, they all read approx. 580 / 590 Mohms.

Mohms? This would be resistance between the two pins on the bottom side of each transformer. Should be a lot lower than that, I think, like a few Kohms. Maybe 580 ohms?

Could you be a bit more specific about the 'cap being a little bulged'?

This is the cap under the three reddish power resistors, top center of the power board picture. Rather than the top being flat, it looks like it has bulged up a little.

Failed capacitors look fine at first. Then internal pressure causes them to swell, usually at the stamped vent on the top. Then they leak, from the vent if you're lucky, from the bottom if you're not. Leakage is black or rust color, possibly others. It's corrosive, and should be cleaned off the board.

From what I can see, there's a component (don't even know what it is), very small, sitting between the (main) connector and a 16 legged IC, it has white stuff all over - Is this normal?

Can't find what you're talking about. The white goo is glue to hold components in place. It's normal.

[ipanini]

Re: Another Samsung Syncmaster 245B - Solved!

Hi Folks,

Thanks for your terrific help! And thanks for your wonderfull forum too!!
I inspected RB805, RB806 and RB807. It appeared TB805 was open / dead.
Picked one up at the local store, soldered it back in place, and the 245B is back in business again!!

Many, many thanks!

Erwin