Samsung SyncMaster 731N Screen on and off.

[sceva]

Re: Samsung SyncMaster 731N Screen on and off.

Now the issue is that monitor goes black when windows start

When turning on the computer press F8 and start up the computer in VGA mode and see if it stays on. If so then the display settings on the computer need to be changed to match what the monitor requires.

[uligli]

Re: Samsung SyncMaster 731N Screen on and off.

When turning on the computer press F8 and start up the computer in VGA mode and see if it stays on. If so then the display settings on the computer need to be changed to match what the monitor requires.

I did that already, also tried to enter the safe mode but still the same, i have to mention that it happens with linux too. Does anyone know how to reset the EEPROM?

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

Trace this back to the connector to the logic board. The inverter is being switched off, then back on. Relevant components are J505, R501, D501 C518 and R518. It appears R501 has a crack across it, but it couldn't be that simple. Probably something complex like a bad solder joint.

PlainBill

PlainBill... after checking all these components, and finding nothing wrong... I resolder them all, no change. So I went back to square one and found that the on/off signal coming from the logic board was going from the 3.3vdc to 0 when the screen went off. I'm not sure how I missed this... except maybe the meter I was using? Slow response time? ANYWAY, I missed it. So I checked everything below with a good calibrated Fluke 83 on the logic board:


(all pins not listed were 0Vdc with screen on and off)
U101 AS1117L-33
B0618
Pin 2: 3.32Vdc on/off
3: 5.18Vdc on & 5.07Vdc off
4: 3.32Vdc on/off


U102 AS1117L-18
B0552
Pin 2: 1.80Vdc on/off
3: 5.16Vdc on & 5.06Vdc off
4: 1.80Vdc on/off


U103 24C02W1
0628G
Pin 5: 4.31Vdc on/off
6: 4.31Vdc on/off
8: 3.32Vdc on/off



U108 24C02W1
0629J
Pin 5: 3.31Vdc on/off
6: 3.31Vdc on/off
8: 3.31Vdc on/off



U106 Pm25LV010
AE0634
020481C

Pin 2: Fluctuated from 1.38Vdc to 1.26Vdc when on and 1.11Vdc to 1.45Vdc when off. *NOTE* at one point while checking and rechecking these measurements... this pin was steady at 1.17Vdc... and the monitor stayed on for a long while. When I shut it down, and turned it back on... it start fluctuating again. I'm not sure what I did to get it to stay on??
Pin 3: 3.31Vdc on/off
5: Fluctuated from 2.13-2.29Vdc when on and 2.24-2.35Vdc when off.
6: 1.08Vdc on/off
7: 3.31Vdc on/off
8: 3.31Vdc on/off

Any ideas?

[PlainBill]

Re: Samsung SyncMaster 731N Screen on and off.

PlainBill... after checking all these components, and finding nothing wrong... I resolder them all, no change. So I went back to square one and found that the on/off signal coming from the logic board was going from the 3.3vdc to 0 when the screen went off. I'm not sure how I missed this... except maybe the meter I was using? Slow response time? ANYWAY, I missed it. So I checked everything below with a good calibrated Fluke 83 on the logic board:


(all pins not listed were 0Vdc with screen on and off)
U101 AS1117L-33
B0618
Pin 2: 3.32Vdc on/off
3: 5.18Vdc on & 5.07Vdc off
4: 3.32Vdc on/off


U102 AS1117L-18
B0552
Pin 2: 1.80Vdc on/off
3: 5.16Vdc on & 5.06Vdc off
4: 1.80Vdc on/off


U103 24C02W1
0628G
Pin 5: 4.31Vdc on/off
6: 4.31Vdc on/off
8: 3.32Vdc on/off



U108 24C02W1
0629J
Pin 5: 3.31Vdc on/off
6: 3.31Vdc on/off
8: 3.31Vdc on/off



U106 Pm25LV010
AE0634
020481C

Pin 2: Fluctuated from 1.38Vdc to 1.26Vdc when on and 1.11Vdc to 1.45Vdc when off. *NOTE* at one point while checking and rechecking these measurements... this pin was steady at 1.17Vdc... and the monitor stayed on for a long while. When I shut it down, and turned it back on... it start fluctuating again. I'm not sure what I did to get it to stay on??
Pin 3: 3.31Vdc on/off
5: Fluctuated from 2.13-2.29Vdc when on and 2.24-2.35Vdc when off.
6: 1.08Vdc on/off
7: 3.31Vdc on/off
8: 3.31Vdc on/off

Any ideas?

Very few. I would say the most likely cause is the video processor chip on the logic board is defective. The regulators are stable; the variation in the 5V supply is due to the power supply voltage varying slightly. The only other suggestion is to see if it is possible to do an eeprom reset. This involves holding down several buttons while plugging the monitor in.

PlainBill

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

Very few. I would say the most likely cause is the video processor chip on the logic board is defective. The regulators are stable; the variation in the 5V supply is due to the power supply voltage varying slightly. The only other suggestion is to see if it is possible to do an eeprom reset. This involves holding down several buttons while plugging the monitor in.

PlainBill

You wouldn't know what buttons to hold, would you?

Also... any idea why, once, the monitor was on steady?

[PlainBill]

Re: Samsung SyncMaster 731N Screen on and off.

You wouldn't know what buttons to hold, would you?

Also... any idea why, once, the monitor was on steady?

Not a clue. Google 731N reset, Samsung monitor reset, etc.

The EEPROM reset is sort of a last ditch attempt. I'm not optimistic it will fix it, but it's a step that shouldn't be neglected.

I actually believe the video processor is fried. The story as I heard it goes like this. One of the consequences of eliminating lead from ICs is that Bad Things happen to the connections inside the package. Specifically, on a microscopic level pure tin tends to grow whiskers. These can lead to shorts between adjacent contact points on the die.

PlainBill

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

Ah... Thanks PlainBill... the resets I've found, don't work. Guess this monitor will become a spare part machine, unless I can find a Main Board cheap.

Thanks again for the help. I've learned more about monitor repair on this monitor alone than all the others I've fixed. BTW... where did you learn so much about this stuff? I'm always looking for more resources to further my knowledge? I did buy the only book on LCD repair I could find: LCD Monitor Repair by Jestine Yong. It is helpful, but...

[PlainBill]

Re: Samsung SyncMaster 731N Screen on and off.

Ah... Thanks PlainBill... the resets I've found, don't work. Guess this monitor will become a spare part machine, unless I can find a Main Board cheap.

Thanks again for the help. I've learned more about monitor repair on this monitor alone than all the others I've fixed. BTW... where did you learn so much about this stuff? I'm always looking for more resources to further my knowledge? I did buy the only book on LCD repair I could find: LCD Monitor Repair by Jestine Yong. It is helpful, but...

I've been dabbling in electronics since the days where 'rectifier' meant 5U4. As each development came along I tried to absorb at least the essentials. One of the things I learned fairly early is that if you understand at least a little of the theory, troubleshooting is much easier.

It also helps that some of the elements of an LCD panel go back more than a half-century. The 'inverter' traces it's ancestry back to the days when car radios had vacuum tubes, and a chopper (vibrator) was used to convert 6VDC to the 75 VAC which was rectified to provide the plate voltage for the audio output tube. And that concept went back to to at least the Ford Model T Spark Coil.

Another thing is the greatest resource is right at your fingertips. Take the SMPS controller as an example. Search for the datasheet on one - the SG6841SZ. It basically walks you through the design of a power supply. Many of the other elements of an LCD monitor can be researched the same way.

But the best resource is the posts here. I think it's an open secret that Dell and HP both sell monitors built by Benq - and they have the same problems. The possible reason for the failure if the ICs was from an article I came across somewhere. You can learn more about it by Googling tin whiskers rohs.

PlainBill

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

Thanks PlainBill... I'll look that stuff up.

I learned a lot of electrical theory in the Navy, but it is coming back. My hardest part is not having prints... I find myself drawing prints of the LCDs as I go.

[PlainBill]

Re: Samsung SyncMaster 731N Screen on and off.

Thanks PlainBill... I'll look that stuff up.

I learned a lot of electrical theory in the Navy, but it is coming back. My hardest part is not having prints... I find myself drawing prints of the LCDs as I go.

Agreed. I've found a few resources; I'm sure there are many more. Now that I think about it, that might make a good FAQ 'Where To Find Schematics'

http://elektrotanya.com/

http://english.electronica-pt.com/

http://www.s-manuals.com

PlainBill

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

Thanks! That will be an invaluable help.

[smason]

Re: Samsung SyncMaster 731N Screen on and off.

The possible reason for the failure if the ICs was from an article I came across somewhere. You can learn more about it by Googling tin whiskers rohs.

PlainBill

Wow, some fascinating reading, I hadn't heard about tin whiskers before.

[PlainBill]

Re: Samsung SyncMaster 731N Screen on and off.

Wow, some fascinating reading, I hadn't heard about tin whiskers before.

This is one of my peeves. I fully appreciate how hazardous lead can be in the food chain. Decades ago I had an object lesson on just how much was dumped into the environment from leaded gasoline. There are very good reasons it should not be used in paint, or in any item which can conceivably come into contact with food.

But to ban it from the inside of an IC that's encapsulated in plastic is asinine. It's bad enough we have to put up with bad solder joint, the fact that the IC is slowly destroying itself is mind blowing.

PlainBill

[newbie1]

Re: Samsung SyncMaster 731N Screen on and off.

This is one of my peeves. I fully appreciate how hazardous lead can be in the food chain. Decades ago I had an object lesson on just how much was dumped into the environment from leaded gasoline. There are very good reasons it should not be used in paint, or in any item which can conceivably come into contact with food.

But to ban it from the inside of an IC that's encapsulated in plastic is asinine. It's bad enough we have to put up with bad solder joint, the fact that the IC is slowly destroying itself is mind blowing.

PlainBill

Ahhhh!! Tin whiskers...

just to share.
In my short (12-13 years and counting.. lol) span of earning a living as a failure analyst (read 'post mortem' fella to dead ICs), tin whiskers failure is definitely in the Top Billboard Chart for the Most PITA failures to analyze. I still recalled having to spend weekends in the lab, lapping/grinding away the shorted IC, layer-by-layer in MICRONS, just to expose the damned whisker shorting the leads INTERNALLY. AFAIK and correct me if i am wrong, tin whisker will grow faster with moisture. A colleague and i did one experiment where we biased an adjacent lead-free pins with a drop of water in between them. We watched in awe, under the microscope, as the tin whisker grow just like a tree with all the leaf & branches. lol.

Other than tin whiskers, ICs will possibly also fail due to Electrical Over Stress (EOS), Electrical Static Discharge (ESD), environmental factors, etc. ICs with 'hard' parametric (read open/shorted) failures are easier to analyze than those having 'intermittent' or functional failures where reliability risks are high. And ICs failure are irreparable, which is somewhat depressing. So, that's one reason why i indulge my new past time, in reviving 'dead' LCD (which i believe the success rate is definitely higher) instead.
LOL!.

[uligli]

Re: Samsung SyncMaster 731N Screen on and off.

I did that already, also tried to enter the safe mode but still the same, i have to mention that it happens with linux too. Does anyone know how to reset the EEPROM?

I fix the problem by removing the resistor and make a bridge at pin 5 to 6, now the monitor works flawless.

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

uligli... which resistor did you remove? And pin 5 & 6 of what?

[uligli]

Re: Samsung SyncMaster 731N Screen on and off.

uligli... which resistor did you remove? And pin 5 & 6 of what?

Please see post #18, pic #3. I soldered a 47 ohm resistor at the ic chip, to fix my problem i had to put more voltage so i removed the resistor and made a bridge.

Your monitor is different than mine, so i can only recommend you:
1) resolder all the boards
2) check logic to lcd panel's cable
3) recap all except the big one on the inverter/psu board (including the small caps, today i fix my vp930b that had display issue by recaping a 10 uF 50v cap)

Don't give up

[billy66]

Re: Samsung SyncMaster 731N Screen on and off.

Please see post #18, pic #3. I soldered a 47 ohm resistor at the ic chip, to fix my problem i had to put more voltage so i removed the resistor and made a bridge.

Your monitor is different than mine, so i can only recommend you:
1) resolder all the boards
2) check logic to lcd panel's cable
3) recap all except the big one on the inverter/psu board (including the small caps, today i fix my vp930b that had display issue by recaping a 10 uF 50v cap)

Don't give up

Thanks uligli. I believe my power board is good... getting correct voltages and steady. My logic is what is giving a bad signal. The main IC chip is telling the system to shut down... this chip is most likely bad on my board. I may try to recap this board anyway (practice) and see what happens. The IC pin 84 (or 85, I forget) is suppose to send 3 volts out to turn on a transitor... which then send the 3.3 volts to the power board telling it to turn on the lamps... this pin is giving the correct voltage, but after a few seconds or more, it then goes to zero.

But, I'll try anything