Samsung 930b LCD cold start problem (inverter?)

[EGuevarae]

Re: Tech details on green fuse?

Can we get clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

And why only the bulged caps? Caps can go bad even when not bulged (low capacitance or high ESR...).
Replace them all as a rule and you'll save time .....

[alexanna]

Re: Tech details on green fuse?

Can we get clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

Just another sugestion.Samsung boards are very good about identifying voltages on the connector from the power supply to the logic board.
It would be a good idea to verify these, including the backlight on signal.

[retiredcaps]

Re: Samsung 930b LCD cold start problem (inverter?)

I replaced the three bulged caps.. no change.

BTW, most members here including PlainBill would suggest changing all the capacitors except the largest one which rarely, but not never, fails.

Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300.

[retiredcaps]

Re: Samsung 930b LCD cold start problem (inverter?)

The image is viewable with a flash light.. so something is working..

Some inverter board sections have a fuse and it could be open. Or it could be a shorted mosfet or transistor in the inverter section. These components could be on the backside as well and you will need a multimeter to test them.

[Logicsays]

Re: Tech details on green fuse?

Can we clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

Sure.. I'll get a snapshot asap. I have a great camera so I'll post a nice big highly detailed pic. Thanks for your help.

[retiredcaps]

Re: Tech details on green fuse?

My board looks identical to the images in post #60

Can we get clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

1) Post clear focused pictures of your boards using the manage attachments function. Please do not post inline.

2) What brand and series did you use for replacements?

3) If the power LED is on, hookup a working computer displaying your favourite wallpaper. If you shine a flashlight on the screen, do you see the wallpaper?

The image is viewable with a flash light.. so something is working..

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

1) Post clear focused pictures of your boards using the manage attachments function. Please do not post inline.

2) What brand and series did you use for replacements?

3) If the power LED is on, hookup a working computer displaying your favourite wallpaper. If you shine a flashlight on the screen, do you see the wallpaper?

I replaced the caps with the mentioned digikeys replacements. I'll try to the flash light trick again before the caps being replaced I had nothing. I'll update

[Logicsays]

Re: Tech details on green fuse?

In case somebody cares, i just wanted to point out the procedure described earlier in the first posts also works with a faulty Samsung 930BF. Apparantly the PCB-Layout isnt much different and the problems are the same.

But has somebody managed to identify exactly the little green fuse? or at least has more technical specs about it? I just shortend it with a wire instead and it works, hope that wont affect the other circuits in a bad way...

Where is this fuse? My board looks identical to the images in post #60 Is it right next to the 3 caps in the white rubber goo?

[retiredcaps]

Re: Samsung 930b LCD cold start problem (inverter?)

1) Post clear focused pictures of your boards using the manage attachments function. Please do not post inline.

2) What brand and series did you use for replacements?

3) If the power LED is on, hookup a working computer displaying your favourite wallpaper. If you shine a flashlight on the screen, do you see the wallpaper?

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

I replaced the three bulged caps.. no change. Solid green light nothing else.

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

Forget the fuse. Replace the caps!!!!

PlainBill

Thanks.. I ordered them yesterday. I'll let ya know how it turns out.

[PlainBill]

Re: Samsung 930b LCD cold start problem (inverter?)

also having a hard time locating the fuse. I viewed images of board posted and mine seems to be a bit different.. would this fuse be next to my caps? I noticed the tops of 3 caps are humped up compared to the rest of the caps.

Forget the fuse. Replace the caps!!!!

PlainBill

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

also having a hard time locating the fuse. I viewed images of board posted and mine seems to be a bit different.. would this fuse be next to my caps? I noticed the tops of 3 caps are humped up compared to the rest of the caps.

[Logicsays]

Re: Samsung 930b LCD cold start problem (inverter?)

I have the same monitor as mentioned in this thread. My symptoms are the green light comes on.. never blinks..just remains solid green. however if you push one of the other buttons.. menu etc.. you can see a faint flicker of light thru out the panel.. hard to see unless its dark... I guess I should start with the fuse?

[tts2271]

definately check fuse F301!

Yes, especially check the fuse F301!

It was the same with my 930BF, changing the 820uF capacitors only brought back the picture with no backlight. After wiring the fuse the backlight came on and the whole display came back to life. Great thing!

[momaka]

Re: Samsung 930b LCD cold start problem (inverter?)

But has somebody managed to identify exactly the little green fuse? or at least has more technical specs about it?

I think it's a 3A fuse. See post #26 and the post after on page 2 of this thread.

I just shortend it with a wire instead and it works, hope that wont affect the other circuits in a bad way...

It won't affect the circuit in a bad way if everything continues to work properly. However, if one of the transistors in the inverter shorts, the whole power supply could get damaged. So with that said, better replace that wire with a proper fuse.

I have this same monitor and had atleast 3 of the 820uf 25v CapXon the visually looked bad so I replaced with 1000uf 25v velleman caps, there was also a 1000uf 10v that looked bad so I replaced it also with the same 1000uf 25v velleman and still can see the check signal cable moving around on the screen when I shine a flashlight at it but even after letting it set plugged in for more than 20 min the screen never gets any brighter any suggestions?

You need to use low ESR caps. The velleman caps you used most likely aren't.
Stick to the good brands like Rubycon, United Chemicon, Panasonic, Nichicon, and Sanyo. As for what series to use from these brands:
From Rubycon, you can use YXG, ZL, and even MBZ
United Chemicon - KY, KZE, LXY, and LXZ
Panasonic - FC, FR, FK, and FM
Nichicon - PM, PW, HE, and HD
Sanyo - WX
Also check fuse F301.

[tts2271]

Tech details on green fuse?

In case somebody cares, i just wanted to point out the procedure described earlier in the first posts also works with a faulty Samsung 930BF. Apparantly the PCB-Layout isnt much different and the problems are the same.

But has somebody managed to identify exactly the little green fuse? or at least has more technical specs about it? I just shortend it with a wire instead and it works, hope that wont affect the other circuits in a bad way...

[RussTime]

Re: Samsung 930b LCD cold start problem (inverter?)

I have this same monitor and had atleast 3 of the 820uf 25v CapXon the visually looked bad so I replaced with 1000uf 25v velleman caps, there was also a 1000uf 10v that looked bad so I replaced it also with the same 1000uf 25v velleman and still can see the check signal cable moving around on the screen when I shine a flashlight at it but even after letting it set plugged in for more than 20 min the screen never gets any brighter any suggestions?

[retiredcaps]

Re: Samsung 930b LCD cold start problem (inverter?)

Eventually, it will not display any image at all, the power led just blinks rapidly, none of the buttons on the monitor respond, and no OSD is displayed.

1) Do you see the display if you shine a flashlight at it?

2) Well, the caps look visually okay, but they could still be bad. Let's assume, for now, they are good and start with measuring voltages.

3) If you have a multimeter, take voltages readings on the connector between power board and the logic board. You should get 5V DC on least one of the pins and possibly 12V or 19V DC as well.

4) If you don't see the voltages above, then carefully measure the DC voltage across the large main capacitor. Careful, it is mains * 1.4 voltage.

5) Also, you may have to desolder that green board that is upside down to get a picture. One person had a problem with a Samsung monitor about 5 weeks ago and it was a component on that board that was the problem.

6) There is also a red fuse right next to the green board. Check to make sure the fuse reads less than 1.0 ohms.