Samsung syncmaster 710v

[Mr_Bodgit]

Hi all,

This is my first post, just spent ages looking around this section at faults to see if i can shed some light on my problem! i know some electronics and know my way around around a pcb lol


anyhow, heres what iv got/found/done etc

monitor powers up with display then after a minute (or seconds the longer its been on) the screen turns off, power light stays on!

now i'v found the bad power caps (2x470uf, 1x1000uf, 1x330uf) power is ok (+13v and +5v to video card and +13v to the inverter part of board,

the monitor stayed on for ages last night after changing the caps, then it went off (slight hissing, getting slightly louder before turning off),

so i set about searching around the board for any voltages dorpping off!

when the screen goes off i found that a mosfet (AO4422) that looks like it turns the inverters on (0v switching) is ending up with the inverters supply voltage showing up on the negative output side of the mosfet (0v supply on pins S, +6v to turn it on on Pin G, switched 0v output on pins D) see pic

the only componants i can find between +13v supply and the switched 0v output that could do this is two diodes SS24 (2A 40V Schottky)

not had time to remove them yet but does this sound right?

i checked the bulb life using that service menu! 46k hours its been on, it was used in a police station for the cctv lol

Regs
Richard

[retiredcaps]

Re: Samsung syncmaster 710v

now i'v found the bad power caps (2x470uf, 1x1000uf, 1x330uf) power is ok (+13v and +5v to video card and +13v to the inverter part of board,

What brand and series of capacitors did you use for replacement? In addition, did you replace all the capacitors or just the bloated ones.

i checked the bulb life using that service menu! 46k hours its been on, it was used in a police station for the cctv lol

46K is near the end of the useful life of your ccfl tubes.

Just a quick clarification question. Right now, what does the lcd monitor do when you power it on? Does the power LED stay on? Do you get the screen staying on?

edit: Forgot to ask you to post clear focused pictures of your board. If you have been reading posts here, you know the format we want it in (via manage attachments).

[Mr_Bodgit]

Re: Samsung syncmaster 710v

i took the better looking 470uf and 1000uf ones from another faulty monitor

yeah i know bad idea but the power supply outputs are ok no matter what happens, +13v and +5v on volt meter, there only smoothing caps as across + & - outputs so cant see it being them.

the supplies and power LED stay on when the screens tubes goes off, the supply to the inverter part of the board goes to +15v when screen goes off but thats due to less power being consumed i guess

it stays on for about 10 seconds the starts to hiss slightly near the to diodes i listed

only the 0v changes to +13v on the supply to 2 transistors marked
DK
QL

i dont have a good camera to post any yet sorry

Regs
Rich

[retiredcaps]

Re: Samsung syncmaster 710v

it stays on for about 10 seconds the starts to hiss slightly near the to diodes i listed

Everyone has different procedures and starting points. For hiss and given the 47K hours, I would start by looking at the ccfl tubes to see if they are bad or have poor wiring. These pictures will help you determine which is which.

http://s807.photobucket.com/albums/y...klight%20lamp/

Alternatively, you can measure the inverter transformer secondaries to see if there is a problem there. This hissing could be coming from there too? This testing requires much less work than the above.

[mockingbird]

Re: Samsung syncmaster 710v

46K is near the end of the useful life of your ccfl tubes.

Not necessarily. Fluorescent tubes are more apt to die from repeat on/off cycles than length of use. If it was used as a CCTV, chances are it wasn't turned on or off that often.

Granted, 46,000 hours is a lot.

[retiredcaps]

Re: Samsung syncmaster 710v

Not necessarily. Fluorescent tubes are more apt to die from repeat on/off cycles than length of use. If it was used as a CCTV, chances are it wasn't turned on or off that often.

Granted, 46,000 hours is a lot.

This is where I got my info from ...

http://ccflwarehouse.com/faqs.html

Q: What is the typical life of a CCFL lamp?

A: The typical rated life of a CCFL backlight is 20,000 to 40,000 hours, however when used in LCD applications such as laptops you should expect between 1.5 and 3 years of use from most manufacturers.

[alexanna]

Re: Samsung syncmaster 710v

Troubleshoot as if it was a 2 seconds to black problem.
Easiest way I know substitute known good ccfls [if you have them]
Al.

[Mr_Bodgit]

Re: Samsung syncmaster 710v

tested it with one tube at a time, stays on half the time, bottom tube turns screen pinkish for few second then normal.

just tried the sceen (just ccfl's) from the other monitor and no hissing or turning off for the min i left it on! CCFL's it is by looks of it, the joys of being given two matching monitors lol i'll swap the power board over and check bulb life on the other one in a min

regs
Rich


update
other one has 47332Hr
but its staying on!!!!!!!!!!

the power board for this screen had the power light coming on but then of wound make a noise and flicker off the back on in a continuous cycle, screen wouldn't light up, as no power for wake up, oh well one out of two isn't bad for nowt.

cheers guys

[retiredcaps]

Re: Samsung syncmaster 710v

tested it with one tube at a time, stays on half the time, bottom tube turns screen pinkish for few second then normal.

Pink is sign that the ccfl lamps are nearing end of life. If you want to fix both monitors, ccflwarehouse.com sells bare lamps, pre-wired, and/or pre-assembled. Or you can just be happy with the one fixed monitor and keep the other for spares?

If the police used these 24/7, then implies 5.5 years of usage.

I haven't commented on the caps yet, but after 5.5 years of 24/7, the original caps may be near end of life too. They don't have to bloat to be bad.

[Mr_Bodgit]

Re: Samsung syncmaster 710v

yeah i guess they would, will tinker with the other one over xmas and replace the caps anyway,

will look into tubes

now i'll be making sure work bring all the old ones back from sites so i can mess with them

Regs
Rich

[retiredcaps]

Re: Samsung syncmaster 710v

As ccfl lamps age, they draw more and more power. This causes the inverter pwm chip to shut down all the lamps even though only one might be bad (protection).

If you are going to order lamps, you have a decision to replace just the "bad" one or all of them. Replacing just the bad one is like replacing the baldest tire, but leaving the other 3 originals on the car (especially since these monitors have > 45K hours).

This leads to an economic decision on your part.

[Mr_Bodgit]

Re: Samsung syncmaster 710v

the monitor has been on for hours now and works fine, i'm not bothered about doing the tubes just yet cos we get these all the time so i can just keep tinkering lol

but this has got me thinking now becos i have two touchscreen computers that that i got from a steel works and these were on 24/7,

the inverters have EMAX PLCD2817418 but IEI / 7F700-PLCD2817418-RS / INVERTER(D->A);4CCFL 7.5MA FOR MEDICAL comes up on net

it has a simple 4 wire connection to pc, supply voltage +/- is fine and stays on, not checked the power on/brightness voltage yet but will do later today

the screens light up for a few seconds in POST! then go off, turn it off and back on the same happens so i stuck a graffix card in and windows works fine, as does the touch screen

just looked at the card and two hermei 150uf 25v caps are swolen and there linked to the mosfets that turn the ccfl's on so i'll start there

the 2 ccfl's are 4 wire with two little plugs (my samsung monitors are 3 wire 2 pink, one smaller white so cant use them to test) whats best way and cheapest to test the inverter once the caps are done if it still goes off?

[alexanna]

Re: Samsung syncmaster 710v

the 2 ccfl's are 4 wire with two little plugs (my samsung monitors are 3 wire 2 pink, one smaller white so cant use them to test) whats best way and cheapest to test the inverter once the caps are done if it still goes off?

The style of the connector should not be a problem.
Note the orientation of the wires in the connector.
It a little extra work but the connectors can be changed, I use a capacitor leg inserted into the small hole of the connector to remove the wiring pigtail from the connector. Then install the pigtail in whatever style connector you need.
Al.

[Mr_Bodgit]

Re: Samsung syncmaster 710v

The style of the connector should not be a problem.
Note the orientation of the wires in the connector.
It a little extra work but the connectors can be changed, I use a capacitor leg inserted into the small hole of the connector to remove the wiring pigtail from the connector. Then install the pigtail in whatever style connector you need.
Al.

what i ment was its a 4 tube inverter, 4x2pin (only pink wires), the sreen i have is only 2 tube, 2x3pin (two pink, one white) whats the white wire for? and can you still test only using the pinks?

regs
Rich

[alexanna]

Re: Samsung syncmaster 710v

Well a pitcure would be hepful,from what i have noted the pink wires are the hot wires the white wire is the return wire.They are most likly sharing the common white wire with more than one ccfl
Al.

[alexanna]

Re: Samsung syncmaster 710v

This is probably not like yours, but it shows how two hot wires share one common white wire
Al.

[Mr_Bodgit]

Re: Samsung syncmaster 710v

thats exactly like my samsung one