Hanns-G HG281D, LCD Monitor no power

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

Hey Guys,

i just found this Thread via Google. I read some of the pager here and hope you can help me with my HG281D.

Today after updating and restarting my computer it just stopped recognizing any inputs.
Ive tested 2 Computers over HDMI and 1 over VGA. It seems to recognize when a connection is made, because it shows the green box "No signal....". But after that it doesnt show any picture and just goes back to sleep.
I never had any problem wit this monitor before!

Did somebody here have this problem before, or knows which parts/boards i have to check?

Thanks in advance!

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

"Did somebody here have this problem before, or knows which parts/boards i have to check?" The power supply board and the logic board. more likely they need to be recapped.

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

^ What budm said.

Usually C80 and C83 are the caps that fail most often on the logic board. They are known to cause all sorts of issues when this happens.

You can find more info and some useful links I collected from other people in the second half of my post here:
https://www.badcaps.net/forum/showpo...&postcount=604

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

The other two did turn on and +5VSB was stable, but did not get the signal (displayed "no signal" message). Replacing capacitors C61 and C69 on the main board (100 uF / 16 V next to a regulator) fixed them. Just a hint for other people looking for a quick fix and not wanting to spend more than a dollar for spare parts :-)

Thanks guys,
Ive just read through all posts here and came to the one above with exactly the same problem. I will change all of the caps and hope for the best!

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

So, i just changed all the Caps on the Mainboard (not the Powerboard) and the monitor is still giving me the "no signal" message.

Any ideas?
Should i replace the caps on the Powerboard?

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

Changed all Caps on the powerboard.
Problem persists.

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

I hope somebody is still reading this

Problem: Always get "no signal" message when connecting or disconnecting hdmi.

I already changed all the caps on both boards.

Here are some high resolution pics:
1
2
3
4

[Lumberjack777]

Re: Hanns-G HG281D, LCD Monitor no power

You could check the 2 voltage regulators on the top left (in your picture 3)
Here's a good video explaining it - https://www.youtube.com/watch?v=cNFzBJELFoU

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

Hey, thank you for your suggestion!

i just measured the two voltage regulators. But nothin seems off to me...

The bigger one has an input of 5.1V and an output of 3.3V.
The smaller one has an input of 3.3V and an output of 1.8V.

All voltages are stable when connecting something on HDMI or pressing on/off.

Edit: PS_On (the black cable between power and main) measures 0.02V when amber led and 2.84V when display on.... somewhere in this thread was said that it had to be over 3V?!

Edit 2: It seems the powerboard is working fine. For the short time the display is on, the 24V/12V and 5V are stable.

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

"PS_On (the black cable between power and main) measures 0.02V when amber led and 2.84V when display on.... somewhere in this thread was said that it had to be over 3V?!" >2.5 = ON, <1V = OFF.
At this point it seems to me that the logic board is not sensing the Video signals (you have already verified that the PC and the cable are OK), you will have to use the scope to find out if the Video and sync signals get all the way to the processor or not and to do that you will need the diagram also.

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

Yeah, i checked the cable and laptop on another monitor. There they are working fine.

Thank you very much. I think verifiyng the videosignals and processor is something i cant do with my limited electrical supply and knowledge.

I will wait another week if someone has another idea. After that its going into the trash if no one is interested.

perhaps i should mention that this problem did start after rebooting the pc.

[_BtB_]

Re: Hanns-G HG281D, LCD Monitor no power

Hello, have a question about this monitor.
When it is turned on, the blue light would come on but it would take a long time for the picture to show. I guess once it is properly heated, the picture would show and everything would be good until windows puts the monitor in sleep mode or I turn off the monitor.

Does this sound like a capacitor problem? I do not see any bulges in the caps, but the caps could be dried causing high esr correct? I will get some pictures when the sun is out later on today.

Also I remember this forum having a tutorials section where one could learn basic electronics through the links provided, is this still a thing? Maybe it was another forum or something... But if you could recommend books or video tutorials for the absolute beginner I would appreciate it, thanks

[Marauder2003]

Re: Hanns-G HG281D, LCD Monitor no power

My problem is similar to BtBs problem

Not sure which board in my HG281D needs caps. For a long time it took many presses of the on button before the screen came on. Then one day the power went out and when it came back on the monitor did to. Apparently the on-off system remembers the last state. This lead me to use a power cord with an on-off switch so I did not have to use the monitors switch.

The monitor takes over 15 seconds to come on. And the longer it is off the longer it takes to come on. But once on it is fine. All inputs work. No flickering.

Any idea which board needs caps?

[Lumberjack777]

Re: Hanns-G HG281D, LCD Monitor no power

To both of you. It sounds like the caps on the power board. If your power board is the same as this attached picture, replace the 3 circled in red. Those 3 are known to dry up. If after the power board is working, you notice any fuzziness or pixelation; replace the 2 caps on the main/logic board. (in the 2nd picture)

On this power board the manufacturer tended to bend the legs of the caps completely over on the pads. Making them a little harder to remove without lifting the pads. You'll want to remove the solder with desoldering braid, then heat the area with the tip of the iron and take a very small screwdriver and bend the pins up a little. The goal is to remove the cap without lifting the pads.

For BtB - There's some great videos on youtube on how to solder properly. I'd practice on an old spare board first. Then solder the new caps on the power board. Good luck

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

I hope somebody is still reading this

Problem: Always get "no signal" message when connecting or disconnecting hdmi.

I already changed all the caps on both boards.

Here are some high resolution pics:
1
2
3
4

Are these pictures after you changed the caps? If so, I see one potential problem: you used Teapo capacitors (or so it appears to be by their vents) - those are known to be quite unreliable. You might also have used the wrong series of Teapo (i.e. not low ESR or not low enough).

The voltage on the regulators you measured appears to be fine, but bad power/excessive ripple due to faulty caps (or caps not adequate for the job) could still cause issues. I had one LCD monitor where all voltages came up properly and appeared "normal". However, the image on the display would not always display properly - sometimes, I would just get a bloack screen, other times random pixels. I replaced just a few of the output caps on the power supply with proper caps and that got the monitor working perfectly afterwards. So it is important to use good caps.

What qualifies as good caps? - The major Japanese brands: Panasonic, Nichicon, Rubycon, and United Chemicon. And you also have to get the right low ESR series. So...
Panasonic: FC, FM, and FR
Nichicon: PW, PS, PM, HE, HD, HW
Rubycon: ZL, ZLH, ZLJ, ZLG
United Chemicon: KY, KZE, KZN, LXV, LXY, LXZ\

Do NOT use eBay if you are new to buying capacitors - there are way too many counterfeit capacitors on there, especially from China/Hong Kong. Local shops likely won't have what you need either. The best place to get capacitors is online through some of the better-known part suppliers, such as Digikey, Mouser, RS Online, and Farnell/element14.

[TVRepairNoobie]

Re: Hanns-G HG281D, LCD Monitor no power

Does anyone think the low solder on this chip might be a problem?

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

Are these pictures after you changed the caps? If so, I see one potential problem: you used Teapo capacitors (or so it appears to be by their vents) - those are known to be quite unreliable. You might also have used the wrong series of Teapo (i.e. not low ESR or not low enough).

The voltage on the regulators you measured appears to be fine, but bad power/excessive ripple due to faulty caps (or caps not adequate for the job) could still cause issues. I had one LCD monitor where all voltages came up properly and appeared "normal". However, the image on the display would not always display properly - sometimes, I would just get a bloack screen, other times random pixels. I replaced just a few of the output caps on the power supply with proper caps and that got the monitor working perfectly afterwards. So it is important to use good caps.

What qualifies as good caps? - The major Japanese brands: Panasonic, Nichicon, Rubycon, and United Chemicon. And you also have to get the right low ESR series. So...
Panasonic: FC, FM, and FR
Nichicon: PW, PS, PM, HE, HD, HW
Rubycon: ZL, ZLH, ZLJ, ZLG
United Chemicon: KY, KZE, KZN, LXV, LXY, LXZ\

Do NOT use eBay if you are new to buying capacitors - there are way too many counterfeit capacitors on there, especially from China/Hong Kong. Local shops likely won't have what you need either. The best place to get capacitors is online through some of the better-known part suppliers, such as Digikey, Mouser, RS Online, and Farnell/element14.

I just saw your answer, thanks!
i got all the capacitors from Conrad here in Germany. Sadly they only provide one cap for a special rating (V and F). So there wasnt really a choice.
But shouldnt there have been at least a slightly change in symptoms after changing the caps?

Most of the people with bad caps in this thread first did have only little problems and with time they got bigger up to total failure of the monitor.
But my monitor just stayed black after reboot, it was perfectly fine before!
So my guess is that it isnt a problem with slowly drying caps rather than something that broke because of short hight voltage burst or something similiar. (Probably the monitor-cpu?)

If i find the caps mentioned by you, I probably will try them out!

[fightforlife]

Re: Hanns-G HG281D, LCD Monitor no power

Does anyone think the low solder on this chip might be a problem?

What is the best way to make sure these soldering points make a correct connection?

Ive read that some guys put their graphicscard into the oven for a short time. Can i use this method with the mainboard or will the caps get damaged from the heat?

My problem is that i only have a rather large soldering iron. So I cant really solder on this small pins. i would only try to heat them i little without fully melting to give them a better connection...

[_BtB_]

Re: Hanns-G HG281D, LCD Monitor no power

hey thanks for the help
the pics posted of the power board are not the same as mine, I managed to snap a few pics but they are not of the best quality. Its the best I could do without buying a camera.

So I will just recap the entire 2 boards and see how that goes. here is the cap list

logic board:
3 x 470uf 16v
12x 10uf 25v
5x 100uf 16v

power board:
2x 1000uf 35v
2x 680uf 25v
4x 10uf 50v
1x 33uf 35v
2x 1000uf 16v
1x 100uf 16v
1x 220uf 10v
1x 220uf 25v

and here is the digikey cart sharing (i think this will work)
http://www.digikey.com/short/7rb0vr

Is everything in the digikey cart accurate?

thanks

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

Does anyone think the low solder on this chip might be a problem?

Interesting find. The solder does look quite ugly indeed. However, if the chip doesn't run too hot (under 60C), then the chances of the solder cracking due to temperature changes is fairly small. But if you tried everything on your monitor and it still doesn't work, then this might be worth a try. I will say, though, that manually soldering those pins with an iron is quite tricky. Hot air should be somewhat easier... but if you don't have a hot air tool, it's not worth getting one just for the monitor.

But shouldnt there have been at least a slightly change in symptoms after changing the caps?

Not necessarily.
The performance of the new caps, if they have the wrong ESR, could still render the same problem.

Think of this as an expriment. You need to eliminate all sources of "uncertainty" before going to the next step.

But my monitor just stayed black after reboot, it was perfectly fine before!
So my guess is that it isnt a problem with slowly drying caps rather than something that broke because of short hight voltage burst or something similiar. (Probably the monitor-cpu?)

Well, the caps going dry overtime could have caused something else to fail too.

Try this: get either a laptop or a second working monitor to hook up to your desktop (and hopefully, your desktop video card has two monitor outputs).

For laptop: after laptop boots, connect your Hanns-G monitor (try both VGA and HDMI if the laptop has one). See if the computer "recognizes" the monitor (Right Click on desktop and go into "Sceen Resolution" [W7] or Properties>Settings [XP]).

For desktop PC: let it boot to you desktop screen with the working monitor. Now connect the Hanns-G monitor, and repeat same procedure as above.

Basically, you're trying to see if the PC "sees" the monitor as connected.

Ive read that some guys put their graphicscard into the oven for a short time. Can i use this method with the mainboard or will the caps get damaged from the heat?

Electrolytic caps will certainly get damaged from the heat. You have to remove them all before trying this.