Re: Samsung 305T bad picture
The transformer in the picture make a buzzing noise. Any ideas? (Check SMPS diagram)....
andrew1
Member
Last Activity: 07-30-2013, 06:56 AM
Joined: 03-30-2013
Location: NY
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Last edited by andrew1; 06-28-2013, 08:19 AM. -
Re: Samsung 305T bad picture
FFC/FPC connectors - OK
T-con voltage - OK
Now I have to check the DVI cable...and last the T-con board....Leave a comment:
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Re: Samsung 305T bad picture
Thanks lexwalker. i'm going to do that.
I have a dell 24+1 DVI dual-link cable. There is no continuity on 24,25 pins. Not sure if that's ok and I don't have a spare cable
. I'm starting to hate this monitor....
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Re: Samsung 305T bad picture
I did that but no change. This is how black background looks. If you look closer you see something like vertical lines. In windows alot of colors are missing in the center of color wheel from color correction section (all are replaced with this color I see on black background)....Leave a comment:
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Re: Samsung 305T bad picture
This monitor has one DVI port. VGA cable is not compatible....Leave a comment:
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Samsung 305T bad picture
Hi,
Sometimes it works flawless. Could be a bad DVI cable or something else? Thank you.... -
Re: Samsung 305T Plus black screen
I'm back with another question if somebody want to help me. I did everything that was told and seams that i'm moving in the right direction.
From mainboard:
BL_EN = 2.7V
Status = 3.3V
all 24V lines are ok.
Problem I found: The inverter IC (BD9886FV) has no input voltage (pin 28).
Look at this pictures for an obvious bad capacitor or maybe you have a clue from where should I start tracking the problem. Thank you.
[ATTACH]63343[/ATTACH]
[ATTACH]63347[/ATTACH]Re: Samsung 305T Plus...Leave a comment:
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Re: Samsung 305T Plus black screen
OK. You can close this thread. Seams that people are not as friendly as I thought. I find it hard to believe that nobody has a clue about step-by-step troubleshooting....Leave a comment:
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Re: Samsung 305T Plus black screen
Back to the drawing board. After two weeks I managed to take all the components back
. The short is gone, the fuses are good...but we have no backlit. Waiting for the next step 
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Re: Samsung 305T Plus black screen
Can somebody tell me from where is sent the "on command" to inverter.
He thinks that this could be the problem.
Reminder: backlit is missing, two blown fuses, at least one mosfet...and now a possible "on command" problem. Need advice fast...make sense what he said? Should I find another service before is to late?
...
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Re: Samsung 305T Plus black screen
Nothing is changed and I can't do anything about it. I have to belive that we have good caps. From what I read there are alot of posible problems. A transformer or bad CCFL lamp can activate the protection on the inverter board and the backlight will stay off untill you remove them from circuit. I will let him try to fix the problem a few more days. If I have a bad CCFL lamp he can't do anything 
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Re: Samsung 305T Plus black screen
UPDATE: Seams that SMPS and MAIN are good. The inverter has good MOSFETS. Might be something else we didn't think about.
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Re: Samsung 305T Plus black screen
Yesterday I took with me only the inverter. But after I saw the same problem I went back with the other two boards (SMPS and MAIN). They can't do a full test...I called an hour ago and they have no clue about the problem. BTW is not a certified service or anything. Maybe you still can help me find the problem. I'm thinking if both fuses are blown...the problem should be with the inverter or maybe CCFL lamp? Thanks....Leave a comment:
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Re: Samsung 305T Plus black screen
I realised that I can't do it by myself...mosfets have 8 pins and I need a heat gun to change them. Everything was done in a service. I told the guy from there to change caps and mosfets but he said one mosfet is bad...and the rest are good. When I went home I saw the same problem...so I decided to let him take a look at SMPS, MAIN & INVERTER. Maybe the problem is not so simple...or he did a mistake by not changing all four mosfets and caps...not sure. Anyway I don't have any experience and is to complicated for me. Maybe there...Leave a comment:
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Re: Samsung 305T Plus black screen
Still doesn't work. Was tested a few seconds. Fuses are ok but I don't want to try again.
Maybe I should find a service....
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Re: Samsung 305T Plus black screen
I bought everything I need but I have to wait two weeks. I'll keep you posted
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Re: Samsung 305T Plus black screen
Thank you all for your support.
Last question. How many MOSFETs should I buy. 2, 3 ,5?...Leave a comment:
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Re: Samsung 305T Plus black screen
Hi budm. Thank you for corections. I forgot how to read pin order but multimeter was used the right way.
Now that you're mention there is something strange with those two MOSFETs on the right side (S1/D1 only). If you see the last picture I got a few random readings . In 200ohm mode everything is fine "1" but if I switch to diode mode and I measure them a few times at some point I get "0". and if I go back to 200 ohm mode fast there is "0" also for a few seconds....Leave a comment:
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Re: Samsung 305T Plus black screen
So we have two fuses / one MOSFET but the main problem is not yet found. I will replace that mosfet later...for now let's move on to the next step.
I want to ask you a question. How we found out that we have a short circuit in the inverter? Is because I got a short between ground and one end of the fuses? or is just because these bad fuses show an increase in current after...not before them. I wonder what would happen if I connect the mainboard to the inverter and measure the ohms between mainboard ground and the...Last edited by andrew1; 04-02-2013, 11:15 PM.Leave a comment:
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Re: Samsung 305T Plus black screen
budm. I think so, alot of them, all in the first row have the same code.
Tried your method with 200 Ohms scale.
Now it show "1" everywhere with one exception - 2nd MOSFET. The one I was sure it was bad.
Can you verify if these are the right pins?
1-5 / 1-6
3-7 / 3-8
Thanks....Leave a comment:
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