Problems with Samsung 740N monitors

[qbicdesign]

Re: Problems with Samsung 740N monitors

To everyone posting here, this thread is gold dust!
I have one 740n with the 3 blown caps (which i already replaced) and the blown 3A picofuse, which I'm waiting on.

I also have 3 of the 740n monitors with the circuit board from pic 1 referenced here on the very first page in this thread:
https://www.badcaps.net/forum/showpo...18&postcount=4

I'd like to know if (beyond replacing the bulging caps), is there any fuse replacement on this board?

[Behemot]

Re: Problems with Samsung 740N monitors

Can't see anything, the picture is terrible. It may very well be under the second board, just have a look yourself, fuse is F.

[qbicdesign]

Re: Problems with Samsung 740N monitors

seems I have answered my own question.

I replaced the bulging 1000uf 10v with a 16v which I had salvaged from an old mobo.
There's a single 470uf 25v which lays horizontally next to the mosfet board. I didn't have a same replacement, but figuring that the board printing states 13v, i put a 470uf 16v there (also salvaged from an old mobo).

The 3 monitors are now working!

There are some other still bulging CapXom capacitors rated at 470uf 25v, which I'll replace as soon as I can get to the store. But as proof of concept, I know that my monitors are OK.

The cool thing is that I have about 40 740n monitors, which seem to be dying on a fairly regular basis with all the same symptoms (flashing blue light, no image on screen), and now I know how to fix them all

All of those monitors shared the same symptoms, same swollen caps, in all the same locations. It should be enough to switch out (per monitor) 3x 470uf 25v, 1x 1000uf 10v.

Again, thanks to all posters in this forum for your contributions!

[Behemot]

Re: Problems with Samsung 740N monitors

I can supply you with quality caps, maximum capacity in each dimension and too extremely low ESR. PM me for more information…

[skydec]

Re: Problems with Samsung 740N monitors

Just repaired 2 samsung 740N LCDs.
On the first one I just replaced the 3 capacitors on 13V rail and that was it, worked after that.
Second one was a bit tough. It was completely dead, LED also dead. Fuse, thermistor and varistors were OK. ZD102 was found dead, replaced it but it didn't help. After I powered the LCD still nothing, replaced zener didn't burn. Comparing ohm readings form first LCDs psu I saw lower ohm readings across several components in primary side of the second LCDs psu (Zener diodes were not reading as (600,infinity) but (200,200). So I decided to swap the DM0565R and now the second psu is also working. The faulty DM0565R was not in short circuit but still is not working properly.

[tvl_svl06]

Re: Problems with Samsung 740N monitors

Problems with Samsung 740N monitors

samsung 740n monitor display in 2 sec.. go to screen block mode

display time inverter input voltage 14.0v
inverter power input 18.5v this voltage is normal?
change 470mf25v cap.3no,1000mf25cap no1
send more information

[Behemot]

Re: Problems with Samsung 740N monitors

Seems like open-circuit voltage is high, should be OK under load. Replace all caps, usually all of them go bad even though it may not be visible. Check inverter transistors and transformer(s), everything is coverd many times in this thread.

[tvl_svl06]

Re: Problems with Samsung 740N monitors

change all cap,cheeking inverter transformer normal

[selldoor]

Re: Problems with Samsung 740N monitors

change all cap,cheeking inverter transformer normal

No use saying transformer is normal - what are the secondary
winding resistances.

[tdr]

Re: Problems with Samsung 740N monitors

I changed the bad caps and now I got the screen running but with some vertical colored stripes on the right side of the screen. Is that because of loose connection somewhere and can it be fixed? Thank you.

[Behemot]

Re: Problems with Samsung 740N monitors

Try reseating the LVDS but it may bad panel too.

[tvl_svl06]

Re: Problems with Samsung 740N monitors

af4502c mosfet equlant

[Behemot]

Re: Problems with Samsung 740N monitors

You can buy 10 of them from eBay for 2 bucks free shipping http://www.ebay.com/itm/10PCS-MOSFET...item3f2a9b8e7d

[tvl_svl06]

Re: Problems with Samsung 740N monitors

Samsung 740n white screen

[Behemot]

Re: Problems with Samsung 740N monitors

Reseat LVDS cable, than bad display.

[tvl_svl06]

Re: Problems with Samsung 740N monitors

reset cable no display

[tvl_svl06]

Re: Problems with Samsung 740N monitors

Samsung 740n some line vertically,no display

[tvl_svl06]

Re: Problems with Samsung 740N monitors

monitor screen shot

[ghost52+]

Re: Problems with Samsung 740N monitors

Hi.I am new member and i have a problem with this monitor.It doesn t turn on and it hasn t the stby light on.I take the ps board to look at it but i didn t see something blown up or the capacitos in a bad condition.Any idea what to do?

[tvl_svl06]

Re: Problems with Samsung 740N monitors

how to solve this problem