Hanns-G HG281D, LCD Monitor no power

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

OK, the capacitors are installed with correct polarity? if they are, then use ohm meter and check the resistance between the two legs of each one of those two caps you replaced to see if it shows shorted circuit due to solder bridge. Recheck and verify that all the cables are connected back in place correctly.

[davisgarth09]

Re: Hanns-G HG281D, LCD Monitor no power

OK, the capacitors are installed with correct polarity? if they are, then use ohm meter and check the resistance between the two legs of each one of those two caps you replaced to see if it shows shorted circuit due to solder bridge. Recheck and verify that all the cables are connected back in place correctly.

All cables have been re-connected about 4 times now. Maybe the polarity is incorrect? After the re-cap, the first power on attempt showed a blue then orange light (no picture). The second attempt and any following attempts show no lights.

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

Maybe the polarity is incorrect?

Stripe on each capacitor goes to the white shaded semi-circle on the board. Check your work and maybe even post pictures of it.

[davisgarth09]

Re: Hanns-G HG281D, LCD Monitor no power

Stripe on each capacitor goes to the white shaded semi-circle on the board. Check your work and maybe even post pictures of it.

Re-capped it with NEW caps, correct polarity this time, still no power. My soldering iron isn't the best, I may have heated the board to much during the soldering/de-soldering process, I noticed the solder was having a hard time sticking to the cap's and the board.

Maybe I should purchase a new board?

I know with a new board comes the same crummy caps, but it may be better to re-cap a new board then attempt to re-cap this one again?

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

My soldering iron isn't the best, I may have heated the board to much during the soldering/de-soldering process

I doubt it. The board can take a lot of high heat cycles as long as you don't peel the pads where the caps solder to. Both too little and too much heat can damage the pads. If your iron is rated between 25W and 40W, let it heat for at least 5 minutes before trying to solder anything. If it's a 50W iron or more, it may need just a minute or two to heat up fully, if even that much.

I noticed the solder was having a hard time sticking to the cap's and the board.

Are you using rosin-core solder flux? If not, you may want to get some (or alternatively, get "no-clean" flux, apply to the solder joints, and heat with your iron again).

Maybe I should purchase a new board?

Post pictures and we will see.
There is also a chance that your power supply start-up caps could have gone bad. No power at all is a sign of bad start-up caps in the PSU. This thread covers both. Some had issues with those, while others with the mainboard, like you.
If you have a multimeter, we can even help you troubleshoot or at least somewhat help conclude if your main board is bad and that this is not a power supply issue.

I know with a new board comes the same crummy caps...

Precisely why a new board is not needed, unless you really "mess" things up badly.

[davisgarth09]

Re: Hanns-G HG281D, LCD Monitor no power

I doubt it. The board can take a lot of high heat cycles as long as you don't peel the pads where the caps solder to. Both too little and too much heat can damage the pads. If your iron is rated between 25W and 40W, let it heat for at least 5 minutes before trying to solder anything. If it's a 50W iron or more, it may need just a minute or two to heat up fully, if even that much.


Are you using rosin-core solder flux? If not, you may want to get some (or alternatively, get "no-clean" flux, apply to the solder joints, and heat with your iron again).


Post pictures and we will see.
There is also a chance that your power supply start-up caps could have gone bad. No power at all is a sign of bad start-up caps in the PSU. This thread covers both. Some had issues with those, while others with the mainboard, like you.
If you have a multimeter, we can even help you troubleshoot or at least somewhat help conclude if your main board is bad and that this is not a power supply issue.


Precisely why a new board is not needed, unless you really "mess" things up badly.

Thanks for the thorough reply. I have a multimeter but not a ESR meter. My soldering iron has a more Flathead like tip on it, I cannot locate my other tips. I will take some pictures of my tools/solder/PSU/Logic Board and get them posted ASAP.

I had a hell of a time trying to get the old caps off, It took 10-15 minutes before my iron was hot enough to get the solder to melt. I believe I may have messed up a pad on the c80 cap, I will take detailed pictures of these as well.

[Lumberjack777]

Re: Hanns-G HG281D, LCD Monitor no power

Re-capped it with NEW caps, correct polarity this time, still no power.

So you did have at least one in backwards once? That could cause problems with other components.

I had a hell of a time trying to get the old caps off, It took 10-15 minutes before my iron was hot enough to get the solder to melt. I believe I may have messed up a pad on the c80 cap, I will take detailed pictures of these as well.

If you did mess up the board or connections you can always run a piece of wire from the capacitor lead to where the copper trace went to the next component. I sometimes just use a clipped lead (wire) from a capacitor to connect the two.

Here's an excellent tutorial/video on how to solder correctly. https://www.youtube.com/watch?v=I_NU2ruzyc4

[davisgarth09]

Re: Hanns-G HG281D, LCD Monitor no power

So you did have at least one in backwards once? That could cause problems with other components.



If you did mess up the board or connections you can always run a piece of wire from the capacitor lead to where the copper trace went to the next component. I sometimes just use a clipped lead (wire) from a capacitor to connect the two.

Here's an excellent tutorial/video on how to solder correctly. https://www.youtube.com/watch?v=I_NU2ruzyc4

I believe one of the two caps replaced may have been in backwards, that is correct.

Thanks for the helpful video, I learned a few things from it. I know the tip I have now is not ideal for this application, I will be purchasing some new tips and an additional cap kit for both boards next week. What kind of solder would be best for this? Lead-free w/ flux core?

[Lumberjack777]

Re: Hanns-G HG281D, LCD Monitor no power

What kind of solder would be best for this? Lead-free w/ flux core?

No, you wanted leaded solder w/flux core. It doesn't crack as easy. Has a lower melting point. And it's a little easier to solder with. I uses leaded solder on all my projects.

We'll try and see if we can't get this board fixed. It's through hole soldering and that's what makes it harder. You can check out more soldering videos from the same guy "Curious Inventor" on youtube. He's really taught me a lot. Good luck!

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

I had a hell of a time trying to get the old caps off, It took 10-15 minutes before my iron was hot enough to get the solder to melt.

Sounds like you have a weak iron. What wattage is it rated for? If less than 30W, you'll need something better. "disposable" 40-60W irons can be bought for cheap online (like less than $5 shipped). If you are not going to do repair too much, it's probably better to get one like that (although, I will also caution you to never leave such irons unattended, since they are not exactly high quality).
Also, try going for something with a big, chisel or bevel -type tip. Small tips loose their heat quickly and make it hard to solder with. They are usually more suite towards small surface mount components.

Lastly, I recommend to add a tiny bit of fresh solder to your iron's tip before trying to solder or desolder anything - this will yield better heat transfer between the tip of the iron and the component's lead, and will make the soldering much easier. Should take no more than 2-5 seconds to heat a joint to get the solder to flow smoothly.

I believe one of the two caps replaced may have been in backwards, that is correct.

Those caps may be damage now. Possibly something else too. But we will see with the pictures, and if you have a multimeter, we can troubleshoot.

[johnwin909]

Re: Hanns-G HG281D, LCD Monitor no power

Hello, my monitor recently started showing rows of blacked out pixels and corruption. Anyone have any idea if this may be a problem with bad capacitors?

http://tinypic.com/r/14b3rll/8

[selldoor]

Re: Hanns-G HG281D, LCD Monitor no power

Its along the bottom -yes? Do you clean the screen with liquid/foam cleaner?

Could be a damaged panel

First thing to try would be to remove clean and replace the lvds cable.

[johnwin909]

Re: Hanns-G HG281D, LCD Monitor no power

Actually yes I did clean the screen with a liquid cleaner. I will try that, thank you.

[davisgarth09]

Re: Hanns-G HG281D, LCD Monitor no power

Here are some pictures of the boards. Also, would this suffice to repair the logic board: http://www.ebay.com/itm/Hanns-G-HG28...item2339edb9a5 (the new soldering iron would be nice, my current iron is a Weller SP23L). Suggestions for an iron/caps/solder etc would be greatly appreciated!

The scratches are from my iron slipping while I was attempting to remove the old caps.

[Lumberjack777]

Re: Hanns-G HG281D, LCD Monitor no power

Ok. First of all that "kit" is for the power/inverter board. Not the main/logic board. The Soldering iron is an el-cheapo that you can get on eBay for around 5 bucks. But they usually work. And burn out after a few hours.
You could buy a similar iron on eBay. (5 bucks or so) Buy your caps from Digi-Key. Buy the solder anywhere (leaded with flux core). And you'd be set.

In the 4th picture the 2 holes look rather large. Did you pull out the metal plated core by chance? Like a metal tube. If so, you'll need to bridge to the components they were connected to.

Also, when soldering, sit up close and brace the front of your body against the bench. And put your elbow on the bench (the one holding the soldering iron). This will keep the iron from moving while soldering.

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

The scratches are from my iron slipping while I was attempting to remove the old caps.

Do you have to press very hard on the iron to get the solder joints to melt? If yes, my guess would be that you're doing so because your iron doesn't get hot enough. I used to do that too when I first started encountering lead-free joints. Higher wattage iron helps. As I mentioned, 40W is a minimum. 50W to 60W will make it much easier on these multi-layer boards with lead-free solder. Adding flux to the joints before trying to melt them with your iron also hels a lot.

Here's a few inexpensive ones (recommended if you solder rarely):
http://www.ebay.com/itm/60W-IRON-SOL...item2c8828fff7
http://www.ebay.com/itm/Delcast-60W-...item233ce20c70
http://www.ebay.com/itm/YongFeng-Dur...item4868efe0c8
These aren't very high quality, so don't leave them unattended. But as Lumberjack777 noted, they should work.

I don't recommend getting that kit you linked to. For one thing, you don't know the brand and series of the caps included in the kit - they could be good quality or they could be cheap generics that will fail very quickly. Moreover, these are for the PSU/inverter board. Also, the soldering iron is only rated for 30W - that is barely enough to do the job. I just tried to change a small cap on a very old graphics card (GeForce RivaTNT) with my 35W iron, and it barely got hot enough to pull the old cap out.

Lastly, based on the picture of the power supply board you included, I do see some green Taicon caps that may be responsible for causing no-power issue. In general, Taicon caps aren't exactly bad (compared to other crappy capacitor brands), but they aren't exactly reliable either, if heat is involved (which is often true in LCD monitors).
Here's a list of caps on the power supply board that may be responsible for causing no-power:
C8, C31, C32, C33
Although, if you are replacing those, you might as well do CS18, CS20, and all of the other green Taicon caps.

As for the logic board, looks like you have the caps put on the right way now.
So it could be that the power board is not providing power to the logic board or could be that a regulator on the logic board is bad (but I doubt it). This, you can check with a multimeter. First check if there is 5V comming from the PSU board. Should be present on a pin or two on either connectors CNS2 or CNS3 (or both?). Measure voltages with the black probe on your multimeter connected to ground (i.e. any metal part on the case of the monitor, as long as the power supply is installed in the monitor). If there is 5V, then check the voltage on the tabs of the two regulators on the logic board - U7 and U8 (top left, in this picture).

Let me know what results you get. BE CAREFUL when taking measurements on the power supply. In particular, take note of the white line on the bottom of this picture:
https://www.badcaps.net/forum/attach...8&d=1407544792
It separates the primary and secondary sides. Anything on the primary side is dangerous to touch when the monitor is plugged in.

[mj2301]

Re: Hanns-G HG281D, LCD Monitor no power

Got my monitor fixed! Thank you to everyone who set this forum up and the people who helped along the way.

The Problem
Originally the monitor was flickering off then on, and on top of that it would start developing white vertical lines.

The Struggle
I replaced every capacitor on the logic board and the power supply. The logic board was the most difficult, because the leads are so close to one another. Plus, when I started I didn't have a desoldering iron, lesson learned, and I got one. In addition, I had two of the capacitor's traces on the power supply lift, so that was hell.

The Added Headache
Finally when I put everything back together the damn thing had green dots everywhere. I took it apart one last time, thinking that it must be a bad connection somewhere on the logic board.

The Solution
Sure enough I went over the capacitors with a bit more solder, verifying the contacts were completely covered. For added measure, I used my heat gun to round out the soldering, moving quickly as to avoid damage to the ICs and the processor. Once that was done, I put the damn thing back together for the last time. Finally this time around it worked!

The Prize

[mj2301]

Re: Hanns-G HG281D, LCD Monitor no power

Here are some pictures of the boards. Also, would this suffice to repair the logic board: http://www.ebay.com/itm/Hanns-G-HG28...item2339edb9a5 (the new soldering iron would be nice, my current iron is a Weller SP23L). Suggestions for an iron/caps/solder etc would be greatly appreciated!

The scratches are from my iron slipping while I was attempting to remove the old caps.

Don't get the cheap irons on eBay. Go to Radio Shack, they have the desoldering iron and the soldering iron for about $15 each. These will last you for several years of use compared to the cheap ones.

As for the capacitors, I would recommend Panasonics or Nichicon, as they were highly rated for quality on this thread. I bought them through DigiKey, again recommended on the thread. These are the capacitors for both the logic board and the power supply.

Here I have attached the parts list along with the ratings and the quantity. Hope it helps. **Verify your logic board and the power supply capacitor ratings before purchase, as each monitor has slightly different versions.**

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

I would recommend 50~60 Watts iron, and the trick to remove old component is to add more solder to the joint first.

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

I would recommend 50~60 Watts iron, and the trick to remove old component is to add more solder to the joint first.

+1
The Radio Shack desoldering iron is not very powerful - probably just barely enough to remove caps on the logic board. Okay, don't get me wrong, it's a nice desoldering iron, but it's better suited for removing ICs on older single-layer boards.