Fixing my computer monitor

Thread Starter

Koluson

Joined Feb 12, 2023
56
Hi everyone

I have a Samsung monitor that is just over four years old.

Last month when I turned on my monitor, I noticed a crackle from the back of the monitor for a split second, two weeks later I heard it again.

A few weeks ago the split second crackle increased to occurring every few days.

Last night I heard a long crackle and the screen turned off briefly and then back on again. A few hours later there was another long crackle and the screen turned off but this time stayed off. There was no response from the power button and its light would not illuminate.

After a couple of minutes the monitor tried to turn on again and made a crackle but then a few seconds later it turned off again. This continued until I turned the monitor off at the wall.

I read into the crackling noise last month and the consensus is a blown capacitor that is causing this problem. Samsung are notorious for it.

I just pulled apart my monitor and inspected the capacitors on the power PCB but all the capacitors seem fine. I'm wondering if perhaps a capacitor has gone bad without deformity?

I also had a look at the LCD panel PCB. It doesn't have any capacitors.

I have always wanted a go at electronics so I was planning on getting a 20 watt soldering iron kit and some capacitors today but now I am holding off for opinions, advice and guidance.

What do others think?

Power PCB

IMG_20230212_160356677.jpg


LCD panel PCB

IMG_20230212_160137.jpg
 

sarahMCML

Joined May 11, 2019
416
Hi everyone

I have a Samsung monitor that is just over four years old.

Last month when I turned on my monitor, I noticed a crackle from the back of the monitor for a split second, two weeks later I heard it again.

A few weeks ago the split second crackle increased to occurring every few days.

Last night I heard a long crackle and the screen turned off briefly and then back on again. A few hours later there was another long crackle and the screen turned off but this time stayed off. There was no response from the power button and its light would not illuminate.

After a couple of minutes the monitor tried to turn on again and made a crackle but then a few seconds later it turned off again. This continued until I turned the monitor off at the wall.

I read into the crackling noise last month and the consensus is a blown capacitor that is causing this problem. Samsung are notorious for it.

I just pulled apart my monitor and inspected the capacitors on the power PCB but all the capacitors seem fine. I'm wondering if perhaps a capacitor has gone bad without deformity?

I also had a look at the LCD panel PCB. It doesn't have any capacitors.

I have always wanted a go at electronics so I was planning on getting a 20 watt soldering iron kit and some capacitors today but now I am holding off for opinions, advice and guidance.

What do others think?

Power PCB

View attachment 287421


LCD panel PCB

View attachment 287422
It may just be the way it's molded, but is part TH801S, the small black thermistor between the choke and the 220nF capacitor cracked? It's difficult to tell in the photo.
 

MrAl

Joined Jun 17, 2014
11,688
Hi everyone

I have a Samsung monitor that is just over four years old.

Last month when I turned on my monitor, I noticed a crackle from the back of the monitor for a split second, two weeks later I heard it again.

A few weeks ago the split second crackle increased to occurring every few days.

Last night I heard a long crackle and the screen turned off briefly and then back on again. A few hours later there was another long crackle and the screen turned off but this time stayed off. There was no response from the power button and its light would not illuminate.

After a couple of minutes the monitor tried to turn on again and made a crackle but then a few seconds later it turned off again. This continued until I turned the monitor off at the wall.

I read into the crackling noise last month and the consensus is a blown capacitor that is causing this problem. Samsung are notorious for it.

I just pulled apart my monitor and inspected the capacitors on the power PCB but all the capacitors seem fine. I'm wondering if perhaps a capacitor has gone bad without deformity?

I also had a look at the LCD panel PCB. It doesn't have any capacitors.

I have always wanted a go at electronics so I was planning on getting a 20 watt soldering iron kit and some capacitors today but now I am holding off for opinions, advice and guidance.

What do others think?

Power PCB

View attachment 287421


LCD panel PCB

View attachment 287422




If it is a capacitor then it would usually be one of the electrolytic capacitors. The three in that group on the right in that first pic most likely.
It's the electrolytic capacitors in the power supply section that go bad. When they go bad they stop filtering and the under/over voltage detection circuit will shut down the power supply. I've seen this on several devices including a TV, computer power supply, etc.
Once you change the caps the device works like new again with absolutely no shut downs.
If you feel up to it you can just change the low voltage section electrolytic caps out for new ones and test it. They are not extremely expensive.
 

KeithWalker

Joined Jul 10, 2017
3,178
If you don't manage to fix it, there is a very inexpensive way of replacing it. I am using 30" LCD TV sets from pre-HDTV days for three of my computers. I got them from thrift stores for ridiculously low prices and the quality is excellent. Just check that the video inputs are compatible with your computer.
 

bassbindevil

Joined Jan 23, 2014
838
My 27" LCD monitor was free, from the side of the road. I guess an overseas student went home and left their junk behind. Unless there are obvious bad caps (and in my experience they're always obvious), or a known issue like the backlighting inverter, it's easier and cheaper to just replace it with another free/cheap monitor. Try Facebook marketplace, local ad sites, thrift stores, recycling yards, Freecycle. Some monitors have VGA/DVI combined on one connector; they'll work with standard DVI cables, but to get VGA you need a sort of splitter cable. You can buy those cables from places like Monoprice, but I stumbled across one at a thrift store.
 

MrAl

Joined Jun 17, 2014
11,688
My 27" LCD monitor was free, from the side of the road. I guess an overseas student went home and left their junk behind. Unless there are obvious bad caps (and in my experience they're always obvious), or a known issue like the backlighting inverter, it's easier and cheaper to just replace it with another free/cheap monitor. Try Facebook marketplace, local ad sites, thrift stores, recycling yards, Freecycle.
I had a 27 inch Samsung that developed very sever screen burn in persistence. Got so bad i had to replace it. Got a different brand i didnt like the way the Samsung monitor limited the way you could adjust the screen settings.
 

Thread Starter

Koluson

Joined Feb 12, 2023
56
Thanks for everyones replies. I read each and every single one of them.

I ended up getting new caps. Most are Rubycon and Panasonic with running hours of 8K-10K @ 105 degrees. There was however one type of cap I had to get which only runs for 2K hours which I am not happy about, and its not going to be made in Japan. :( The brand is Cornwell Dubilier. I had to go with the best available.

Now I just have to wait until they arrive. :)
 

MrSalts

Joined Apr 2, 2020
2,767
Thanks for everyones replies. I read each and every single one of them.

I ended up getting new caps. Most are Rubycon and Panasonic with running hours of 8K-10K @ 105 degrees. There was however one type of cap I had to get which only runs for 2K hours which I am not happy about, and its not going to be made in Japan. :( The brand is Cornwell Dubilier. I had to go with the best available.

Now I just have to wait until they arrive. :)
The time (hours) is at rated temperature. Hopefully, your monitor doesn't run anywhere close to the rated temp and you'll get 5-10x the rated hours.
 

Thread Starter

Koluson

Joined Feb 12, 2023
56
Its not that I fear that they won't live up to the datasheet. I just wish they would last as long as the others so I won't have to repair my monitor so soon because of that one type of capacitor. But they are the best available so it is what it is. :) The Rubycon's with 8K-10K hours are on backorder and won't be available for 6-8 months.
 

MrAl

Joined Jun 17, 2014
11,688
Its not that I fear that they won't live up to the datasheet. I just wish they would last as long as the others so I won't have to repair my monitor so soon because of that one type of capacitor. But they are the best available so it is what it is. :) The Rubycon's with 8K-10K hours are on backorder and won't be available for 6-8 months.
Hi,

Once you fix it, if this really is the problem, the caps will outlive the device.
Electrolytic caps are the worst but you should get at least 10 years out of them depending on how long the device is turned on for each day.
 

Thread Starter

Koluson

Joined Feb 12, 2023
56
I like your optimism and I hope you are right. The quality of Samsung LCD panels are the best through my eyes and I am very happy with my panel.

It's that 2000 hour @ 105 degree cap that worries me. But we'll see.

My monitor is on 10 hours a day. I am a computer nerd. :)
 

MrAl

Joined Jun 17, 2014
11,688
I like your optimism and I hope you are right. The quality of Samsung LCD panels are the best through my eyes and I am very happy with my panel.

It's that 2000 hour @ 105 degree cap that worries me. But we'll see.

My monitor is on 10 hours a day. I am a computer nerd. :)
Hi,

Yes i have a feeling i got a used model when it was supposed to be new. There was always something strange about it. It was big though allowed a lot of stuff to show up on screen at the same time.

Just buy two caps that way you can get 4000 hours at 105 degrees (haha). Will require one more changeout though.
Seriously though i think you will make out ok since the new cap will be brand new and probably much better quality.

The other thing you can do, if you have room, is use two lower values in parallel. For example, if you need 1000uf you can use two 500uf in parallel of the same basic type with same ESR if you can find them. That will not only allow possibly a longer rated life time but also reduce the ripple current to each cap thus increasing the life again. Two 500uf caps work the same as one 1000uf cap except that the ripple current in each cap is halved which helps with the life span. The ESR can be lower or you can try to match that too by getting the two 500uf caps with twice the ESR as the 1000uf cap, and that will be approximately the same.
So just to be clear, if your cap is 2000uf then you need two 1000uf caps, and if 500uf then you need two 250uf or 220uf caps in parallel.
You do have to have room but sometimes you can get away with a little extra lead length to fit the cap or caps. Not too much though.
What you could do is try the single cap the way you intended too, then if that fixes the problem then you can buy two lower values and replace that one with them. That should ensure you get very long life.

10 hours a day isnt too bad really some computers have to stay on 24 hours a day 7 days a week.

Hey i hope you can get back here once you have the fix(s) in place. Would be nice to hear how this all worked out.
 

Thread Starter

Koluson

Joined Feb 12, 2023
56
Thanks for letting me know about the two cap trick. That makes sense to me. Hehe but I just want my monitor working. I promise you this repair is no hobby. :)
 

wayneh

Joined Sep 9, 2010
17,499
Here's another trick that's a real time saver. On some monitors I've repaired, the power supply delivers a single voltage to the rest of the monitor, often 12V. In that case you can skip the repair and just buy another 12V DC supply (with a suitable current rating). They're very inexpensive, probably less than what the caps alone will cost you.

Some power supplies are far more complicated, delivering multiple voltages and maybe under some kind of feedback control. There's no easy way out in that case.
 

MrAl

Joined Jun 17, 2014
11,688
Thanks for letting me know about the two cap trick. That makes sense to me. Hehe but I just want my monitor working. I promise you this repair is no hobby. :)
You're welcome. Back in the day when i worked in the industry, we often had to parallel many caps to get the required filtering and not let any get hot due to ripple currents. It would be common to use 1/2 inch pure copper buss bar to parallel eight 10000uf, 300v capacitors. These were used in high power converter circuits some up to 30 kilowatts.
 

Thread Starter

Koluson

Joined Feb 12, 2023
56
So most of my caps came today except for one, because Element14 screwed up my order.

I used a soldering iron for the first time. The first cap came off easy, the second a bit harder, and I couldn't even melt the solder on the third.

I read the cause of my problem is not tinning the solder bit. Well, i saw online you can just use solder to tin it, but when I tried to use my solder the solder either dripped off into a ball or vaporised.

Tomorrow I am going to buy one of those hair gel type tins of proper solder tinner.

I teared the circuits on the board a bit, but I didn't break them. I think they will be fine once cleaned up and the new caps are soldered in.

I took a photo of the board for those wishing to admire my A grade soldering skills.

IMG_20230223_224154.jpg
 
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