electronics (capacitors) question - samsung monitor

Sorry I've been busy :/

I desoldered the old caps, ordered replacements for all but the one stonkin huge cap in the middle of the power board. The replacements arrived. I soldered on the first 3... then noticed one little 47uF guy lurking next to a heatsink that somehow I hadn't noticed before. I thought to myself, what are the odds that it was that one there that I missed? It'll probably be fine.

Soldered on the rest of the caps. Turned it on. Far less whine, and the test signal message came on. I thought I had it made. Then I plugged in my cable (from 3 different sources in turn just to be sure) - 1 to 3 seconds of video then black screen.

So yeah. It might not have been the caps. Or it might have been that sneaky little 47uF one. I couldnt do anything except order one. Already spent about £11 on caps, so what's another £1.30 and a little more time? :/ Time will tell.
 
That sneaky cap is to do with the green mode power switch which from what I understand is important for the SMPS efficiency and handles the startup current. Could be an issue with the IC if this is the case but could also be an inverter issue if this is a CCFL monitor.

What is the X5A by the way? I have a few high voltage SMPS caps I've salvaged from new (but faulty for other reasons) power supplies which may be similar.
 
Last edited:
Tealc said:
Could be an issue with the IC if this is the case but could also be an inverter issue if this is a CCFL monitor.
Click to expand...
Yes, its a CCFL monitor.

Tealc said:
What is the X5A by the way?
Click to expand...

It's really well glued in is what it is! :) I was going to leave it and hope replacing Mr. Sneaky would work a miracle, though my hopes are fading fast that this is repairable-by-me or even at all. If it's the CCFL, it might be time to give up. :( I'll keep doing a little bit at a time. "X5A" is definitely a large Samyoung capacitor in the same series as the others NHX or whatever it was. Except bigger. The uF and any other useful info is on the glued down side.
 
Replaced the last small capacitor and it hasnt worked a miracle. Screen now outputs for 1 seconds then its like the light goes out and there is a constant (though much quieter than before) buzzing, like the CCFL is struggling to power up.

https://www.dropbox.com/s/nxce5tcvnf7vn45/monitor.mp4?v=0mcns

listen for the change in buzz when the screen goes off. I know there is another background buzz right the way through - ignore that, it's not from the monitor. Its the high pitched constant buzz from the moment the screen goes off.
 
Last edited:
Try this in a darkened room.
Power up the monitor and wait for the screen to go black and shine a torch to the screen and check if you can see just even a faint image on the screen.
If you can see a faint image on the screen then it is probably a faulty backlight or the driver.
Ideally the light source should be at the back for you to see the image but you will probably find it hard to do this as most of the back is encased in a metal cover and needs lots of work to disassemble.
 
Indeed it is a problem with the backlight, as I thought had been implied. ^^ Yes, there is a picture faintly which is unlit. The issue was whether it was with bad capacitors, the inverter or the CCFL lamps. I dont know how to resolve inverter or CCFL issues and it would require more research and time to fix. I was hoping for wise sage Tealc to come back on with another suggestion. :P
 
I have closely following this thread as I have the exact same problem as you, its even Samsung (different model although). I really had no idea what it was, as all of my capacitors were fine. Yet the it would still boot for 1-3 seconds then the screen would turn black but the audio could be heard. Turns out its the back light as well.
 
Last edited:
If you can see a faint image then there is only 2 remaining possibility a faulty CCFL or the driver/inverter.
I believe the inverter parts are the smd components soldered on the underside of the board.
Can you post a pic of the smd parts on the underside of the board.
Also I recommend you solder back the original small sneaky cap that you replaced (Is it 47uf 50v?).

Replacing the CCFL and actually sourcing one is the hard part cause it is usually uneconomical unless you can actually find an exact cheap replacement.
 
AtaRo said:
ic of the smd parts on the underside of the board.
Also I recommend you solder back the original small sneaky cap that you replaced (Is it 47uf 50v?).
Click to expand...

There are pictures posted above. The "sneaky" one has been replaced by a better capacitor of the same rating - panasonic FC series, so there would be no point desoldering and resoldering the original samyoung capacitor.
 
Have ya tried that well known auction site? I had a faulty Samsung monitor the caps had gone, i replaced them but somthing else on the power pcb had also gone, i searched that site and found a guy in china selling the whole boards for mine and many other monitors for about a ten maybe twenty quid cant remember exactly, maybe you can get the other parts also.
 
Right. Here's where I am with this at the moment.

You can see the TM-09176 is the CCFL transformer which converts mains voltage to 850v AC, according to the PCB. Now this'll be 850v at 50Hz as there are no switchers (transistors) kicking about in the area. You have two connectors CN301 and CN303 but I think as there are a number of parts missing the CN303 connector is probably not in use in this model.

I reckon you'll find the inverter module at the end of whatever connects into CN301 and there's probably something amiss with the power supply or something there. Maybe a photo of that if you can find it. Expect this to be a lot denser packed and more complicated.

At least we know the main power seems ok.

The huge X5A cap is probably just the reservoir cap and is unlikely to have much of an effect on the CCFL as it may be just for DC stuff.

Please do bear in mind I am not fully clued up on CCFL and how they actually work but I think I understand the basics.
 
The connectors you are talking about from the component side:
https://www.dropbox.com/s/rlac5yewyrumy0d/connectors_top.jpg?v=0mcns

The same from underneath:
https://www.dropbox.com/s/icnc5r3v98q2c7q/con2_under.jpg?v=0mcns
https://www.dropbox.com/s/uuj7jpndoh6wdsk/con1_under.jpg?v=0mcns
https://www.dropbox.com/s/opdvprs9d8h3en7/con_mid.jpg?v=0mcns

These connect to two wires which presumably go to two inverter boards which must be in the panel housing?
https://www.dropbox.com/s/6qc35bqau5vwrwz/wires.jpg?v=0mcns

Taking a cover off the back of the panel reveals possibly an inverter board? No obvious damage. https://www.dropbox.com/s/fg69knhaffcioka/on_board.jpg?v=0mcns
 
I seriously doubt that the board shown in the last image is a 850v AC board.

I think that would be the display board actually. Notice the 8 flatflex connections to the LCD itself. Each of those will carry information for a single vertical line. If you look closely you may be able to see the connection lines, 150 I reckon on each flat flex? Fancy counting them?

The inverter will be a sealed box or at least sealed off from the panel with metal tape to make sure none of that 850v magic leaks out into the world and more importantly nowhere near that low voltage display board you have there.

A quick google image search shows this sort of thing.

http://www.honeybee-online.com/usd/...525d08d6e5fb8d27136e95/4/1/411687220001_1.jpg *No hotlinking*

This model has the transformer on board but apart from that you can see two devices which I'm guessing are some sort of transistor that does the switching to high frequency and then a single IC to control the process, this board would normally be isolated by a sheet of plastic which would have to be removed. Hmm maybe this board works the other way around too. Low voltage in on the bottom and HV at the top. Maybe the inverter is not near the panel but off that main PCB somewhere.

Not sure exactly what could have gone wrong with it but the fact it comes on for a second suggests it's not completely blown and may be fixeable.
 
Last edited:
quick update: I was fiddling with it, decided to put it back together for ease of putting it out of the way, set it up again, and tried to use the menus to try lowering brightness and some other tricks you can use when capacitors are on the way out (although we now know that isnt the issue, with the power board at least). I used the OSD menu button to cycle through the display options turning it on and off as I went, and when I got to Dynamic Contrast, it stayed on for a bit longer. So I put it back to that and its still on now after 5 minutes. It doesnt seem as bright as it used to - Dynamic Contrast was the brightest eyeball melting setting the monitor had so I never used it on that. Changing the OSD to any other option results in it behaving the same way - off after 1 second. Does this give any further clues?

EDIT: I reset the menu to factory settings, but still only getting a (quite dim) stable picture on dynamic contrast. The picture is sharp, and if I was to guess I would say that the two lamps at the bottom of the panel arent on since it seems brighter at the top and darker at the bottom.
 
Last edited:
Can you take a pic of the solder side of the board under this high voltage transformer.

If some side of the monitor is dark or not well lit it probably means that either the CCFL on that side is not working or one of high voltage going to that CCFL is not working.

connectorstop.jpg
 
You must log in or register to reply here.
Back
Top Bottom