Hanns-G HG281D 28" TFT - Multiple Problems

[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?

[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

[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!

[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.

[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.

[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

[inkragonor]

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

You should be getting 230V AC x 1.414 (rectified) roughly 325V DC across the main filter capacitor (the big one). Set your multimeter to 1000V DC. Be careful, this is very high voltage. Report what you found.

@retiredcaps: I tested the voltage on all the caps and put my notes into one image file. See attachments. Many of the caps have 0V, and only ONE has 3.5millivolts. What could that mean?
Sorry about the chopped-up pics I posted before, I thought those might be useful. This time I've got full top-down pics.

I've made some dumbass mistakes in the past with mixing up part numbers, polarities, etc. (Oh yea, always double check your polarities to!), and I didn't want this to be another case of same.

@stevekasian: Capacitors have a polarity, meaning a positive and negative terminals? How can you tell which is which? Does that line down the side indicate it? Also, thanks for the list of capacitors! I went through and found and indexed each one, accounting for the ones with upgraded voltages, which I marked with a "u" for upgrade.

...but I'm pretty sure you could get them from Íhlutir (Skipholt 7) and/or Miðbæjarradíó (Skúlagata 63).
...I'll check with Íhlutir tomorrow. They know me so I might be able to squeeze out a little discount, regardless of the decimated economy.
Are there any tools you need at this point?

@VladTI: Holy cow, are you in RVK? I guess so if you are offering to lend some tools! I wouldn't mind borrowing some tools if you have the right stuff. I only have a 100W soldering gun, which isn't precise at all; big rounded tip. I think it's more for automotive work. I've lost the soldering iron with the pointy tip in the move from Atlanta.
Thank you for checking on the capacitors here locally. I would rather get them here and pay a little more than to wait two or three weeks to get them by mail. There is a list of them on the attached image called Index.
I agree with you 100% on the helpfulness of the veterans and everyone! There is no way I would have tried to fix this without the help on this forum.

[stevekasian]

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

@nkragonor:

New question: I hope it's just the capacitors, so now I need to know what to do with them. Is it best to buy the new ones first, then switch them one by one? What do I need to know to buy the same capacitors?

I went through and wrote down the item numbers of each of the caps printed on the PCB along with their respective ratings. Then I double checked them.

Next I ordered the caps and removed each of the old caps from the board in the interim. When I did so, I checked each rating against what I'd written down AGAIN, just to be sure.

When installing the new caps, I checked the labels on the baggies that the caps came in against my list and pulled them out one by one as I installed and soldered each of them in. Sometimes in 2s if they were close together and had the same rating. And upon inserting each of the caps into the board to solder them, I checked the markings on the cap with my notes to be absolutely sure I didn't mix anything up.

I've made some dumbass mistakes in the past with mixing up part numbers, polarities, etc. (Oh yea, always double check your polarities to!), and I didn't want this to be another case of same.

Also: Definitely make note of any PCB traces that become damaged, unstuck, etc., and pay attention to those notes when installing the new caps! I forgot that I'd lifted one of the traces around a hole for one of the caps when desoldering it, and when I put the new one in I just jammed the lead through the hole and it almost got caught on the loop in the trace and peeled it completely off. BAD DEAL. I got lucky and it didn't completely detach - Don't make the same mistake!

[retiredcaps]

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

That's my logical deduction, but I don't know so I'm deferring to you :-).

Hmm, let me re-read this the thread again. I could be getting confused with another problem(s) that I'm helping on.

Multiple power supplies in one device is a head-ache.

[VladTI]

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

[...]Where does one get capacitors? Mail order?[...]

Getting them online would definitely be cheaper, especially if you order more than a few, but I'm pretty sure you could get them from Íhlutir (Skipholt 7) and/or Miðbæjarradíó (Skúlagata 63). I'm going to go over this thread again, see which capacitors have been mentioned (and, frankly, see if this all makes more sense to me the 3rd time around) and I'll check with Íhlutir tomorrow. They know me so I might be able to squeeze out a little discount, regardless of the decimated economy.

That's all I have to contribute at the moment, due to my utter ignorance on the matter, but I'm so glad I found this thread! I have two of those big boys, see, and they're both failing (one for the second time). I'll try not to bother y'all much; I'll mostly be lurking and learning.

Stevekasian: Kudos and a hearty Mazel Tov! Well done and a prime example of sticktoitiveness.

Inkragonor: Are there any tools you need at this point? If you're interested, I'd be more than happy to offer whatever help I can. Again, though, this is all Greek to me at the moment, so I don't honestly know how helpful I'd be.

Badcaps veterans: Fantastic work! I don't think I've ever seen such a helpful bunch on a messageboard... *tips hat*

[stevekasian]

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

@retiredcaps: I believe he is saying he is reading no voltage on the DC outputs. If that is the case, would that not be expected if the "standby" circuit was not coming out of standby and allowing power flow in the rest of the circuit?

That's my logical deduction, but I don't know so I'm deferring to you :-).

@inkragonor: As for those caps at Digi-Key, I can tell you that any of the FM & FC caps will fit perfectly. I am attaching a copy of my order so you can enter the part numbers into the "Part #" field at their website if you like. Mouser Electronics was actually cheaper by a dollar or so for the whole order, but I saved on 1st Class Mail shipping with Digi-Key so I went with them.

Under "Customer Reference", I added voltages in parentheses which refers to items where I was able to increase the voltage rating from the original without increasing the size of the cap.

Also added Logic Board caps as well :-)

[retiredcaps]

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

New pics attached.

BTW, we would prefer one overall topdown picture of the power board versus 5 chopped up sections.

[retiredcaps]

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

I tried again with the ground at the hole next to the outputs, but still get zero at the 24, 12, 5 and 5SB(?). What could cause that? Can capacitors do it?

Normally, I put all the screws back in so I know I have a good ground point.

If you are still getting 0V DC, then you have another problem.

You should be getting 230V AC x 1.414 (rectified) roughly 325V DC across the main filter capacitor (the big one). Set your multimeter to 1000V DC.

Be careful, this is very high voltage. Report what you found.

Can I still do the hair dryer test?

Not until you get power.

Is it best to buy the new ones first, then switch them one by one? What do I need to know to buy the same capacitors?

You need to know the uF, voltage, height, and diameter.

Where does one get capacitors? Mail order?

Once it gets to that stage, most here like digikey.com. You can get good quality caps like Panasonic FM there. Caps cost less than $1 USD each.

[inkragonor]

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

Yes, that is a fuse in your picture.

Thanks. It seems to be working fine.

Yes, you want to measure DC voltage on the secondary side. Your ground, though, should be a ground screw closest to your measurement point. That is, put your black probe on a ground screw.

I tried again with the ground at the hole next to the outputs, but still get zero at the 24, 12, 5 and 5SB(?). What could cause that? Can capacitors do it?

Yes, you will eventually have to remove it because there are at least 2 smaller caps underneath that heat sink.

Done. New pics attached.

For the hair dryer test, try heating up the 8 caps on the right hand side of the power board.

Can I still do the hair dryer test? I've got the monitor all taken apart. I guess I only need the ON light to ignite to know if it works or not... I'll try tomorrow.

New question: I hope it's just the capacitors, so now I need to know what to do with them. Is it best to buy the new ones first, then switch them one by one? What do I need to know to buy the same capacitors?

I've only been living here since April, and I don't know any stores that have electronic components. Where does one get capacitors? Mail order? Of course then I have to pay tarriffs (~15%) and taxes(~25%). Yeah, importing to Iceland sucks! How much do capacitors cost? Sorry to be such a newbie!

[retiredcaps]

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

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.

It runs so cool now there's hardly any heat coming off of it at all after hours of use.

Normally, caps on the logic board are not subject to the same abuse/heat as the power board.

But if your monitor ran that hot, it could have dried out all the caps on the logic board.

Glad to see you got it resolved. Good patience.

[stevekasian]

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

[retiredcaps]

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

Checked on the other side of what I believe is a fuse (marked F1 on board, see picture), and it measured 230V also.

Yes, that is a fuse in your picture.

Am I right to measure the output voltage in volts DC? Also, I connected the meter to the main negative coming in from the wall.

Yes, you want to measure DC voltage on the secondary side. Your ground, though, should be a ground screw closest to your measurement point. That is, put your black probe on a ground screw.

Am I going to have to remove that heat sink? It's soldered down.

Yes, you will eventually have to remove it because there are at least 2 smaller caps underneath that heat sink.

For the hair dryer test, try heating up the 8 caps on the right hand side of the power board.

[retiredcaps]

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

I just picked up two of the Hannspree monitors (HF289H)

Good job on the repair and thanks for sharing.

PS. Please, we prefer that you do not post inline and use the manage attachment feature so that the picture is posted here and not offsite. Offsite has the potential for unwanted popups and other nasty URL redirection.

[Ritalin]

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

I just picked up two of the Hannspree monitors (HF289H) that has the same power board and I replaced the capacitors shown below with slighty higher voltages for the bigger ones, and the small ones I did the same values. I got one to work just fine, but ran out of capacitors for the 2nd one, so hopefully it's the same fix.

[inkragonor]

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

Took monitor apart. Checked to see if voltage was reaching the power board, it measured 230V. Checked on the other side of what I believe is a fuse (marked F1 on board, see picture), and it measured 230V also.

I'm not sure I'm doing this right, but I also checked the outputs that are marked 24V, 12V and 5V, but they all measured 0V. Am I right to measure the output voltage in volts DC? Also, I connected the meter to the main negative coming in from the wall.

I hope the pics are okay. I can take more. Also, I see one big capacitor under the heat sink marked 420V, 150uF. Am I going to have to remove that heat sink? It's soldered down.

Also put a picture of the meter I have. Hope it'll do.