Problems with Samsung 740N monitors

[c_hegge]

Re: Problems with Samsung 740N monitors

In this case, the menus do NOT have the red tinge, so it looks like its the same problem pedro was having. As a workaround, I adjusted the color settings in the menu, and its better now. I had it on all afternoon yesterday playing Flight Sim X and no problems, so it looks like its going to be OK.

[vlayza]

Re: Problems with Samsung 740N monitors

I want to thank you all you guys for this thread. I've replaced 3 capacitors, but never saw pico fuse and didn't know why my monitor is still not working. You helped me to find pico fuse, thank you all!

[EGuevarae]

Re: Problems with Samsung 740N monitors

In this case, the menus do NOT have the red tinge, so it looks like its the same problem pedro was having. As a workaround, I adjusted the color settings in the menu, and its better now. I had it on all afternoon yesterday playing Flight Sim X and no problems, so it looks like its going to be OK.

Holy mother of God...... Please. Can't you distinguish between an uncalibrated screen color and a Pink, uniform, all-over-the-place-and-anywhere-you-see red/pink titn on a failing screen?

[sequille]

Re: Problems with Samsung 740N monitors

do u mean that we can transform every monitor into a nice LED display ?
u will use something like this ?
http://www.dealextreme.com/details.dx/sku.5312
Please make a post when u finish ... i think it will be great And will solve many problems with that inverters and lamps ...

Well, there are some reports on the internet of people already doing that. There was a page that was even selling a conversion kit, but it was for laptop screens, thus priced accordingly ($100+).
Yes, that is the type of led strip that i'm planning to use, however i'm waiting for them to release a higher density one. The highest density i saw was 240 Led/metre (which i think is enough) but it was only on chinese wholesale sites, so i'm waiting for importers to put them on their sites. 'Till then, my monitor is waiting in the box

[tj_style]

Re: Problems with Samsung 740N monitors

After several months I can use my LCD,
but now dead again..
I have to replace three 820uF with 470uF and no problems until yesterday when the problem came back.
My LCD Totaly dead, only the blinking blue lights on power button, no picture and light on display
does anyone know the problem? Thanks and sorry for my bad english..

[EGuevarae]

Re: Problems with Samsung 740N monitors

After several months I can use my LCD,
but now dead again..
I have to replace three 820uF with 470uF and no problems until yesterday when the problem came back.
My LCD Totaly dead, only the blinking blue lights on power button, no picture and light on display
does anyone know the problem? Thanks and sorry for my bad english..

1.- Pics of the board.
2.- What replacements did you use last time?

[ropey]

Re: Problems with Samsung 740N monitors

Hi,
I'm new to this thread but I have 2 x 740N monitors that needs fixing, the symptoms seem to be bad caps. Can some helpful person please show me an easy way to remove the back cover without breaking fingernails etc. The Disassemply intructions are professionals with tools and jigs as shown in the official docos

Thanks

[ropey]

Re: Problems with Samsung 740N monitors

Hi,

I have worked it out.
Tools required:-
1 x Oyster shucker
1 x small blade screwdriver
Gently prize from one corner, twist and fit small screwdriver into prized open slot. Work systematically around using shucker twisting and levering it open, then placing screwdriver into prized open slot (same as shucking an oyster only you don't need a screwdriver)

Thanks

[bsweasel]

Re: Problems with Samsung 740N monitors

Ok, here goes. Great forum!!! I'm new. Electronic Newbie attempting fix.

Samsung 730b same PS as everyone is posting here. Symptoms: Power LED on, picture can be seen. No back-light what-so-ever.

Read this thread 2 times.

Replaced bulged SAMXON 820uf 25v X 3 w/ digikey part # P11221-ND Panasonic 820uf 25v X 3

Pico fuse F301 was open, replaced w/ digikey Part # F2315-ND

Tested, still same issue, picture with no backlight.

CN2 is showing 5.1v and 13v.

Inverters are 1325 and 1318 ohms cold.

R104 resistor near pico fuse tests to 10ohm as rated, other resistor next to fuse in glue tested to 176 ohm within tolerance of 180ohm +-5%.

Replaced SAMXON 1000uf 10v X2 for fun with some used ones...no change in symptoms. Any ideas I can try??

Pic 3 Key. Red = Replaced Green = checked while I was there in the area.

Pic 1 - Top side
Pic 2 - Bottome side. (no making fun of my soldering! )

[PlainBill]

Re: Problems with Samsung 740N monitors

Ok, here goes. Great forum!!! I'm new. Electronic Newbie attempting fix.

Samsung 730b same PS as everyone is posting here. Symptoms: Power LED on, picture can be seen. No back-light what-so-ever.

Read this thread 2 times.

Replaced bulged SAMXON 820uf 25v X 3 w/ digikey part # P11221-ND Panasonic 820uf 25v X 3

Pico fuse F301 was open, replaced w/ digikey Part # F2315-ND

Tested, still same issue, picture with no backlight.

CN2 is showing 5.1v and 13v.

Inverters are 1325 and 1318 ohms cold.

R104 resistor near pico fuse tests to 10ohm as rated, other resistor next to fuse in glue tested to 176 ohm within tolerance of 180ohm +-5%.

Replaced SAMXON 1000uf 10v X2 for fun with some used ones...no change in symptoms. Any ideas I can try??

Pic 3 Key. Red = Replaced Green = checked while I was there in the area.

Pic 1 - Top side
Pic 2 - Bottome side. (no making fun of my soldering! )

So close and yet so far...

There is one question you have not asked, so I will do it for you. Why was the pico fuse blown? Hint: Assuming it was not a typo, F301 would be in the inverter area....

PlainBill

[bsweasel]

Re: Problems with Samsung 740N monitors

So close and yet so far...

There is one question you have not asked, so I will do it for you. Why was the pico fuse blown? Hint: Assuming it was not a typo, F301 would be in the inverter area....

PlainBill

I'm not so great at this stuff, so could you answer that great question? I figured it was from the blown caps, but that was just a shot in the dark guess. The new pico has not blown yet....not that it won't as soon as get the lamps to turn on????

[PlainBill]

Re: Problems with Samsung 740N monitors

I'm not so great at this stuff, so could you answer that great question? I figured it was from the blown caps, but that was just a shot in the dark guess. The new pico has not blown yet....not that it won't as soon as get the lamps to turn on????

The usual reason a fuse blows is it was trying to carry too much current. The usual cause is the inverter drivers have shorted. You HAVE answered one question - the fuse hasn't blown again. The question is are the drivers OK?

PlainBill

[bsweasel]

Re: Problems with Samsung 740N monitors

The usual reason a fuse blows is it was trying to carry too much current. The usual cause is the inverter drivers have shorted. You HAVE answered one question - the fuse hasn't blown again. The question is are the drivers OK?

PlainBill

PlainBill, I appreciate the help, but could I ask you to tell me how to test and where to locate the inverter drivers? I can talk the talk, but I can't walk the walk....I have no clue how to identify or test the inverter drivers.

Thanks

[bsweasel]

Re: Problems with Samsung 740N monitors

Attached picture I circled this little 8 pin chip. My eyes aren't the greatest, but the one next to it appears to say

----------
| 45020 |
| AA5RW |
----------

The one circle appears to be a bit burnt on the one side....google didn't turn up anything on those numbers.....anyone tell me what this little chip does? Is this the inverter driver plainbill refered too?

[bsweasel]

Re: Problems with Samsung 740N monitors

Attached picture I circled this little 8 pin chip. My eyes aren't the greatest, but the one next to it appears to say

----------
| 45020 |
| AA5RW |
----------

The one circle appears to be a bit burnt on the one side....google didn't turn up anything on those numbers.....anyone tell me what this little chip does? Is this the inverter driver plainbill refered too?

Ok, now I'm answering my own questions!!

those tiny chips appear to be a 4502C mosfets. But when setting my DMM to diode test and checking per another post I found, both the good looking one and the burnt looking one are getting pretty much the same readings accross the various pins. Which makes me think they are not shorted?? Anyone who is a master care to comment on my findings and maybe point me further. Thanks.

[PlainBill]

Re: Problems with Samsung 740N monitors

Ok, now I'm answering my own questions!!

those tiny chips appear to be a 4502C mosfets. But when setting my DMM to diode test and checking per another post I found, both the good looking one and the burnt looking one are getting pretty much the same readings accross the various pins. Which makes me think they are not shorted?? Anyone who is a master care to comment on my findings and maybe point me further. Thanks.

Well, my eyes aren't anything to brag about either. Those are the inverter drivers, but from this distance I can't tell if that one is burnt or not. A bigger picture would be a big help. And if one is damaged, it's not impossible that both are bad. The usual practice is to replace both if either is bad.

PlainBill

[bsweasel]

Re: Problems with Samsung 740N monitors

Well, my eyes aren't anything to brag about either. Those are the inverter drivers, but from this distance I can't tell if that one is burnt or not. A bigger picture would be a big help. And if one is damaged, it's not impossible that both are bad. The usual practice is to replace both if either is bad.

PlainBill

MY wife took the camera today, so no pictures until tonight.....I think the one is burnt...but I thought it would show shorted on my meter in comparison to the other.
So I guess I could replace both and see what happens? Now to see if I can find the mosfets and wait another couple days for shipping...grrrr.

[bsweasel]

Re: Problems with Samsung 740N monitors

$16.09 worth of parts (shipping included) and a couple hours of a newbie's time and its fixed. My monitor is a Samsung 730B. Replace 3 bad caps, 1 pico fuse and 2 inverter drivers. Replaced the 4502C mosfets with MMDF2C03HDR2G from Mouser.com and bingo, backlights are lit. Monitor fixed. Thank you especially to PlainBill, as well as the rest of the forum contributors this is a great resource!!

[PlainBill]

Re: Problems with Samsung 740N monitors

$16.09 worth of parts (shipping included) and a couple hours of a newbie's time and its fixed. My monitor is a Samsung 730B. Replace 3 bad caps, 1 pico fuse and 2 inverter drivers. Replaced the 4502C mosfets with MMDF2C03HDR2G from Mouser.com and bingo, backlights are lit. Monitor fixed. Thank you especially to PlainBill, as well as the rest of the forum contributors this is a great resource!!

It works!!! All hail bsweasel!!!

PlainBill

[bsweasel]

Re: Problems with Samsung 740N monitors

It works!!! All hail bsweasel!!!

PlainBill

Likewise.....All hail PlainBill!!