Hanns-G HG281D 28" TFT - Multiple Problems

[retiredcaps]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Many of the caps have 0V, and only ONE has 3.5millivolts.

320V DC is good for the main cap.

On CN1, is the 4.95V DC on the pin where it is marked 5V SB?

@stevekasian: Capacitors have a polarity, meaning a positive and negative terminals? How can you tell which is which?

This forum has an excellent recapping tutorial. See

https://www.badcaps.net/forum/showthread.php?t=485

[stevekasian]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

YES, they do! :-) As retiredcaps said above. Just didn't want you to think disregarded your question.

As for your 100W soldering gun, you definitely DO NOT want to tackle this job with that type of equipment. You will most assuredly ruin your PCB by overheating the traces, thereby lifting them off the board itself... not to mention a whole host of other not-so-good possibilities.

Get a 25-35 watt soldering iron with a pointy tip and some ROSIN CORE SOLDER (I've always used 60/40 (tin/lead) type for any PCB work I've ever done.) Those 2 items will fit the job perfectly.

[Mikeley]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Inkragpnor, same time zone as Ireland! Bet it gets dark earlier than 4:30pm!

Your PCB may be discoloured, but it looks ok.... looks like a diode, perhaps a schottky and this might run warm during normal operation. Often these are mounted well above the board to help dissipation. I would not fret about it for the moment.

We need to check if the standby voltage is available at the connector.
I assume you are checking with all boards fitted, screwed into the chassis, all connected up?

In this case the logic PCB will return a voltage (likely to be 5Volts) to the PSU to tell it to fire up. We need to establish if this is happening.

[Kaii]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

@stevekasian

Hey I am new to the board. I have crawled the net and this is the only forum that seems to mention the problem I am having, and you quoted it briefly before - I get those "shimmering vertical pixel lines" you spoke of on my HG281D.

As a description: They only appear to be caused by the green pixels, so appear more pronounced in greener colours. The vertical strips are about 3 pixels wide, and span the entire screen at exactly regular intervals of about 1 inch. They are not dead pixels; its just all the pixels in each of the vertical lines "shimmer". Groups of ~3 horizontally aligned pixels all along the vertical line randomly go white very briefly, giving an overall effect of one vertical line of sparkling dots. Well, about 20 of them across the screen.

I hope I have described that well enough. I don't have a good enough camcorder to record the problem. The problem is annoying but I can deal with it. I would like to fix it though (especially because I want to sell the monitor soon) and it sounds like you managed to fix it.

It would take me all night to read this whole thread and through the adventure of isolating what the problem was, but could you save me the time and tell me exactly what you did to fix this problem (you do not need to go through the detailed how you fixed it, just what you did and I can do the research on how - I don't want to take up too much of your time), if it is indeed one of the problems you were suffering?

If not I will start my own thread, but thanks as a heads up!

[stevekasian]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Hi Kaii,

That sounds pretty similar to one of the issues I was having. I couldn't really narrow it down to a particular color, but it's visibility was definitely affected by whatever was on the screen wherever I was noticing it.

I changed all of the capacitors on the logic board and it fixed the issue. If you look through this thread you can figure out which is the logic board (or "main board').

You will also find a complete order list of the caps I used and their prices. :-)

Good luck!
Steve

[smason]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

The local electronics store wants $30CDN for a solder pump.

Ouch, you're shopping at the wrong store. Let me take a wild guess...
Active?

[retiredcaps]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Let me take a wild guess...
Active?

Went there once, saw the prices, and then went home and placed an order on ebay.

I'm more than happy to support local merchants and businesses, but not at 10x the price.

[Freak Al Franken]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Hello stevekasian,
My unit is powering up and down OK and I can see images on the screen but no back lighting. Getting 24 volts to inverter board but no light.
Some have said it is a logic board problem and I know you replaced caps on it. Did you replace all those little devils????

[retiredcaps]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

My unit is powering up and down OK and I can see images on the screen but no back lighting. Getting 24 volts to inverter board but no light.
Some have said it is a logic board problem and I know you replaced caps on it.

1) If you can see the image on the screen without a backlight, your problem is not on the logic card, it is on the inverter board.

It is likely a blown fuse, shorted mosfet, or shorted transistor.

2) Please post clear focused pictures using the manage attachment button. Please do not post inline.

3) And NO, your board is NOT identical to the OP. Manufacturers make changes all the time and even the slightest change is significant so we want to see pictures of your board.

[fixologist1]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Hey guys... I'm back!

I just got my Logic board caps in yesterday and replaced them, albeit with one hell of a struggle; Those things did NOT want to come off! They used some really crappy looking solder on this board. It was all dark gray and oxidized looking, and kept a very coagulated consistency when liquified. Very difficult to remove with a solder sucker. The best way I found to deal with it was to heat both legs of a cap up at once and just slather a bog ol' ball of 60/40 rosin core solder over both pins, then suck it all up.

This is a tricky board to work with though, because it's double sided - etched on both sides. With each cap, one pin was connected to a trace on the back of the board and the other to a trace on the front side of the board. This means that when using a solder sucker on the pin connected to the back, the solder comes right up. But when you attempt the same with other pin, only the surface solder comes up... because the rest is all stuck down inside the lining of the hole in the PCB. The trace from the front side goes through the hole to the back side, then terminates in a very small surface "ring" to which the component is to be soldered. So the main contact point is INSIDE the hole.

I had to destroy quite a few of the old caps by pulling them off their pins and then just pulling the pins out individually while melting the solder from the back side. This left many instances where the hole was left clogged with solder. In those cases, I stuck the iron tip (very pointy) into the hole on the front side of the board and used the solder sucker on the opposide side to suck it through. (This worked well, but a couple of PCB traces came up in the process... SO BE CAREFUL!) After a while, I realized another method worked even better: Slip one pin of the new cap all the way through the hole that's open and just lodge the other pin into the clogged hole. Then, pushing down on the cap from the front, heat the clogged hole from the back side and it will slide right through.

Also, something to be careful with is the installation of the 4 largest caps along the IC... the 2 470uf and the 2 "taller" 100uf caps next to them (taller then the OTHER 100uf caps found elsewhere on the board). The replacement caps will likely be a bit shorter and fatter, so you'll want to stage 2 or 3 of them at a time BEFORE YOU SOLDER THEM to make sure they're positioned properly for a fit. I had to kind of tweak a couple off to the side, etc., to provide a little more clearance.

Conclusion:

The logic board caps were definitely my problem. The power board caps were causing the thing to run extremely hot, but replacing all of them had absolutely no effect on the video problems I was having. This was absolutely necessary, however, as, if nothing else, they were causing my electricity bill to go thru the ceiling with this thing, and causing some kind of scary-high temperatures inside the case to boot. It runs so cool now there's hardly any heat coming off of it at all after hours of use.

The only issue I have now is that there seems to be a bit of discoloration along the sides and two parallel areas of discoloration along the center, side by side. What it actually APPEARS to be is possibly some darkness on the flourescents - like they're getting old and burned a little bit. But that's just a guess. It's definitely that "yellowish" color that is often times related to bad fl. lighting. But there are a couple of issues that preclude me from being able to get to the bottom of it without more work:

#1. I accidentally counted the caps wrong and was one 10uf 16v cap short... so I looked at all of them with a magnifying lense and chose to keep the one cap that appeared to have no corosion visible around the top crown of it.

#2. Upon installing one of the 470uf 16v caps (the largest ones), I may have pulled on it a little too hard trying to adjust the legs after installation (they were too wide, so I had to bend them to get them to go in with proper clearance). I *may* have damaged the cap in the process, but I'm not sure at all.

So either of these 2 points could be the problem... OR, it could just be that the entire logic circuit has changed enough with the new caps to bring to light some another issue - namely, old fl bulbs that need replacing.

I'm not worrying about it too much though, because the only time it's visible is when I have a giant, maximized empty IE window with a bright white background emblazened across the entirety of the screen. And I try to avoid that annoying sight as much as possible anyway.

It is also worth mentioning that I always used to have barely visible vertical lines of shimmering pixels that would rapidly "sparkle". They were only visible when inspecting the screen very closely, and seemed to be background dependent. They appeared to me to be related to the other screen issues that would appear whenever the monitor was not wanting to cooperate and would keep shutting down, coming back on, etc.

Also, when it would shut down, sometimes it would come back on with a distorted screen. It would be like there were 2 screens superimposed upon one another, with one slightly shifted off the right side of the screen and wrapped around back over on the left side. It would have to shut down again to get corrected.

All of these issues are now Solved. Other than the very minor backlight issue, the screen is absolutely PERFECT and I couldn't be happier!

Thanks again to all you wonderful people who helped on this thread. You gave be the confidence to tackle something I never dreamed I could handle... which saved me about $200!

All the best,
Steve

Stevekasian:

Hi, I have a similar problem as you have described, ( shimmering lines of pixels) but the picture is also shimmering. I am not sure if this is caused by the problem pixels, or if both problems can be resolved by replacing the PSU and Logic Board caps? My monitor does not shut down itself or have any power problems that i can see.

Hope you have some suggestions,

Thanks.

[stevekasian]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Hi fixologist1,

Sorry it's taken so long to respond; I haven't checked this thread in a while!

I would guess that it's probably the logic board caps, as that's what mine was doing even when it wasn't shutting off. I replaced ALL of them. Well, almost. I counted wrong and ordered 1 short, so I left the best looking one on the board. :-/ Count carefully!

SK

[fixologist1]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Thanks Stevekasian!

Ordered the same caps you listed from Digikey +1 extra
Monitor works perfectly now,

Great forum!

[teddyv]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Hi, I found this forum via google because I have problems with this exact monitor..

i have the one Made in Aug 2007 and I been having problems with my monitor making a popping sound when I turn it on Alt tab playing WoW and other apps.

I also starts up when I turn it on and takes a while for the image to show up, Although the image shows up well it starts to flicker from the bottom part of the monitor and then vertical lines appear to shimmer and dissapear.. ive taken the monitor appart and checked to see for any damage and I looked around the board and capacitors to see if anything is burned or damaged.. I took some pics of the boards and I wanted to show the forum to see if i can get any imput on how to fix it..

Any help is greatly appreciated..

Odd I cant add any pics because of this "vBulletin Message
Your submission could not be processed because a security token was missing.

If this occurred unexpectedly, please inform the administrator and describe the action you performed before you received this error."

Anyhow I just put the monitor back together and now the screen is White???

Did I put it back together wrong?

[retiredcaps]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

I took some pics of the boards and I wanted to show the forum to see if i can get any imput on how to fix it..

Pictures should be uploaded using the manage attachments function and please do not post inline.

The maximum pic size resolution is 2000x2000 and I believe 2MB. Resize your pic accordingly.

Anyhow I just put the monitor back together and now the screen is White???

Did I put it back together wrong?

You most likely have a cable that is not seated properly inside the lcd. Reseat all your cables.

[teddyv]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Ty for the Info. I shall reseat the cables and take pics in smaller sizes.

[teddyv]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Hi Again. I uploaded the pics of the monitor boards to flickr and made them public.

http://www.flickr.com/photos/61176240@N08/?saved=1

I hope its easy to fix. ty for taking the time to look at them and giving me a opinion.

[ehren]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

I read through this thread to fix a broken HG281D I bought. I have fixed many others before but have invested much more time into this one. I finally consented to order the caps for the logic board as stevekasian did. Thanks btw. It fixed it. Mine would power on for about 30 seconds then shut off with only the power led 'on'. It also had shimmering in the white of the image. All of that is gone now. Before that, I checked the entire PWB for a problem. I did find 3 bad caps on the power board. C111, C603, C707. Not sure if those affected it in the ways I noticed.

I have a feeling that the problem with the logic board is not bad caps, but bad solder joints. I didn't try it, but if someone wants to try to resolder all of the caps on the logic board to see if it works, I would like the feedback. Of course if that doesn't work, replacing them would verify if the problem lies in this board.

I hope my input can help someone else.

[teddyv]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Oh sweet. thanks for the tidbit there.. I just hope anyone has seen the pics so they can tell me where to soder!

[ehren]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

I replaced all of the caps on the logic board. So... re-solder all of the lytic caps on the logic board and see what happens. Be sure to remove as much of the old solder and replace it with fresh solder.

I might be wrong so don't be too disappointed when it doesn't work.

[teddyv]

Re: Hanns-G HG281D 28" TFT - Multiple Problems

Pictures should be uploaded using the manage attachments function and please do not post inline.

The maximum pic size resolution is 2000x2000 and I believe 2MB. Resize your pic accordingly.



You most likely have a cable that is not seated properly inside the lcd. Reseat all your cables.

I wanted to give an update on my monitor.. Ive pulled out the cables and put them back in again and I still get a white screen. But this time it stays on for a bit and then goes black.. I guessit goes into stand by..

Am i doing something right/wrong?