Hanns-G HG281D, LCD Monitor no power

[banem]

Re: Hanns-G HG281D, LCD Monitor no power

Hi folks.

Wow, 33 pages of posts... and I spent time reading all.

OK, to the point - I have Viewsonic 2835 which has same power supply as Hanss HG281D and a bit similar main board.

I had similar issue - first it would not turn on so I have to remove power cord, put back, remove, put back until it goes on, until 2 days ago when it goes silent dead.

1 year ago I had issue with house power supply. I lost 0V cable so in every wall connector I got around 400V. Since I know why that happens, I immediately switch off whole house power supply, but while I did that, monitor release lots of smoke so whole room was full of it. Since then problems with monitor started and I think something died (maybe part of some IC's). That time varistor protected a monitor and he released that magic smoke.

So I found advises here and I give a try to fix it. A little background - I am into electronic for more than 30 years, few years worked professionally, otherwise mostly as every day hobby, so I have no issues to fix almost anything that does not require heat gun.

First I was about to replace 2 caps on main board in power supply - they were inflated suggesting they lost the value. I can measure capacitance only so I did - both are around 10 uF instead 470!! And monitor worked 3 days ago. I assume they are similar in value and position as in monitor in subject:



I had on hand 2 470/35V not low ESR so I put them instead. I put all back together, not working.

Here is where they are and how they look:



OK, then I went to change those 3 suggested in this thread, 2x22 uF and 1uF. When I took them off I measured capacitance and found 1/4 of capacitance on all.

Since I was lazy to order and wait, I took old Akai CD player, it is like 15 years old and found 2 capacitors 22uF. Measured by capacitance, they are OK (I do not have equipment to measure ESR though) and it appears they are not low ESR. Also I took one new 1uF/160V that I had on stock and replaced all 3. Put all back together, its working! It even turn off / on on every power button click.

Thanks you all! I love the picture this monitor have, actually I hate all those LED litted with cold blue picture (that cannot be set not to be bluish). I am very happy to have this thing working again!

Finally, here is what I replaced, cost is close to zero. I do not think you must use top quality capacitors although it is best to use them to avoid any future issues, as tolerance is very high. My monitor worked with above values!



And all back together in place.

[r3z0nate]

Re: Hanns-G HG281D, LCD Monitor no power

I know there are different models of the logic board but are their different versions of power supply boards? I happened to order (1) 1000uF 35v and (2) 1000uF 25v capacitors going off a list, but have (2) 1000uF 35v capacitors on the power supply board.

I was told I could use the 25v capacitors but would rather repair it properly. If it is just an overkill I'd like to use what I have and get this thing fix.

On a side note, after replacing just the one capacitor my power issues went away but the screen was solid red. Unfortunately the flat cable that goes to the screen broke off on the corner. It should still make the connection, but does anything think that is most likely the culprit? Thanks.

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

I FIXED IT!!!!

I own a HG281D and for many months I had an issue that was described on here. It would basically take several minutes for my monitor to "warm up" and before it did it would turn on and off. After it was warm, it would then stay on. I basically tolerated this for a very long time (probably 6 months or so) and then on occasion it would temporary black out for a second or two depending on what was displayed on screen.

Started doing some research and found this thread. I was able to read through the first 20 pages,... sorry couldn't make it all the way. I ended up ordering a repair kit off of ebay for about $12 (free s/h). I was thinking of buying individually off of digikey but I was worried about the cap sizes not fitting where they were close together. Also, they included some solder remover braid which was helpful. I would highly recommend these kits as they save a lot of time in figuring out what exactly needs to be ordered (yeah, they may cost a few bucks extra).

I'm pretty bad with a soldering iron but I got through it and put everything back together. Magically, about 5 extra screws materialized in the process.

Anyway, the moment of truth came when I plugged it in and bang... it's fixed. I am really happy as I really like the monitor otherwise and saved me a few hundred dollars in replacement costs.

I should note that after examining the power supply and controller board I did not see any "bulging" or leaking caps. So if your having a similar problem but the caps "look good," I would still recommend trying to replace them.

Here are some pictures of the boards, although I couldn't see anything abnormal about them.

PS - Thanks for all the posters on here and the valuable info and pictures people have posted (it really helped when I took off two caps that looked the same yet were different ratings and I didn't know which one went where).

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

Well... unfortunately I don't think it was a complete fix. I did notice that if I turn the monitor off after it's been awhile, then wait for it to completely cool down, and then turn it back on,... there was some flickering. It's definitely much better than it was before and I don't have to wait 10 minutes for it to "warm up." Maybe some other caps are going bad on the other boards? For now it's still very usable so I don't regret doing the work. If it gets worse I will probably try recapping the 2nd board.

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

So did you replace the two caps by the voltage regulators on the logic/main board since most kits have the caps for the power supply repair but not the caps for the main board?

[rspendl]

Re: Hanns-G HG281D, LCD Monitor no power

Just finished repairing four (4) HG281D monitors that all failed after approx 5 years of use. Two did not turn on at all, both had fluctuating +5VSB. Replacing the capacitor C603 of the power supply (22 uF / 35 V) fixed both of them.

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 :-)

[rspendl]

Re: Hanns-G HG281D, LCD Monitor no power

Sorry, the numbers of problematic capacitors on the main board are C80 and C83.

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

So did you replace the two caps by the voltage regulators on the logic/main board since most kits have the caps for the power supply repair but not the caps for the main board?

I only replaced the power supply board caps (except for the large one).

I'm thinking of maybe going back and doing the other board as well. Probably I would order them from digikey if I had a list of all the caps I needed. There are also some larger caps running along the edge of the board attached to the screen, I wonder if I should replace those as well,... although I don't the cap values for that either.

[Lumberjack777]

Re: Hanns-G HG281D, LCD Monitor no power

I only replaced the power supply board caps (except for the large one).

I'm thinking of maybe going back and doing the other board as well. Probably I would order them from digikey if I had a list of all the caps I needed. There are also some larger caps running along the edge of the board attached to the screen, I wonder if I should replace those as well,... although I don't the cap values for that either.

I've repaired about 10 of these. It's always the same caps. The ones on the power board. And the two on the main/logic board as Budm mentioned. If you replace just those 2 you'll probably be fine. Many, many, of the other caps are still good. And it's a waste of time and money to even replace them. Try replacing these 2.

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

I've repaired about 10 of these. It's always the same caps. The ones on the power board. And the two on the main/logic board as Budm mentioned. If you replace just those 2 you'll probably be fine. Many, many, of the other caps are still good. And it's a waste of time and money to even replace them. Try replacing these 2.

I think I will try and replace those two then. Do you have link to a specific cap that you find worked well for you?

[selldoor]

Re: Hanns-G HG281D, LCD Monitor no power

Just use panasonic FM or FR whatever you can get that will physically fit.
Same values as the ones you have.

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

Just use panasonic FM or FR whatever you can get that will physically fit.
Same values as the ones you have.

Would this be a good option: http://www.digikey.com/scripts/DkSea...35008274923241

Sorry if this is a dumb question, I don't know too much about electronics so I rather double check everything before ordering.

[selldoor]

Re: Hanns-G HG281D, LCD Monitor no power

Link doesnt work this is what you need
http://www.digikey.co.uk/product-det...391-ND/2433525

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

Link doesnt work this is what you need
http://www.digikey.co.uk/product-det...391-ND/2433525

Great. Thanks. I made the order so hopefully next week I can give an update on the outcome.

[invenio]

Re: Hanns-G HG281D, LCD Monitor no power

I've repaired about 10 of these. It's always the same caps. The ones on the power board. And the two on the main/logic board as Budm mentioned. If you replace just those 2 you'll probably be fine. Many, many, of the other caps are still good. And it's a waste of time and money to even replace them. Try replacing these 2.

Got the 2 caps for the main board in the mail yesterday and replaced them. Great news, the monitor is working as new. No flickering, no 10 minute warmup,... everything back normal. I wonder now whether there were bad caps on the power board at all. Regardless, thank you for all the help. If I didn't find out about replacing just those two caps on the main board, I probably would not have gone through the trouble of taking it apart again.

For those reading this and having similar problems. Replace those two caps on the main board. It only costs about $3 (with s/h) from digikey for those two extra caps.

[jimmy1256]

Re: Hanns-G HG281D, LCD Monitor no power

OK. I've read all of the pages up to this point, even found the exact problem described that I have. Hanns-G 281D Rev.2. From a cold start the monitor turns on and works fine for about 3 minutes. Then black. LED indicates that its getting a signal from the computer. Using a flash light shows no image. Turn it off/on and I get the image back for about a second. So far I have replaced all of the caps on the power supply and the main board. No change. (probably not a cap issue) Not sure where to go next and am feeling a bit dejected that the caps didn't fix the problems. Any body have an idea what to do next?

[rspendl]

Re: Hanns-G HG281D, LCD Monitor no power

@jimmy1256 Try measuring the voltage at the power supply. If +5VSB is stable all the time (even when the monitor turns off), this circuit is OK, otherwise use better quality capacitors C601/602/603, possibly C707. If some other voltage fluctuates it might be regulators or one of the U(101, 102, 201...) chips. When replacing caps, I've almost broken a pad next to U201 once (as user Steven_C on this forum also did), so try checking whether there was some damage done when replacing caps. Might be something completely different, but this is something to start with. In any case, voltage measurement on power supply is where you should start.

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

OK. I've read all of the pages up to this point, even found the exact problem described that I have. Hanns-G 281D Rev.2. From a cold start the monitor turns on and works fine for about 3 minutes. Then black. LED indicates that its getting a signal from the computer. Using a flash light shows no image. Turn it off/on and I get the image back for about a second. So far I have replaced all of the caps on the power supply and the main board. No change. (probably not a cap issue) Not sure where to go next and am feeling a bit dejected that the caps didn't fix the problems. Any body have an idea what to do next?

If you used good quality caps (i.e., not Radio Shack, eBay for the most part, etc.) and they are low-ESR, then the problem likely isn't cap-related.

Something intermitten like this tells me it could be a bad solder joint or faulty regulator possibly. Since you can't see any image with a flash light when the problem occurs, my guess would be the problem is related either to the logic board (where the signal scaling/processing happens) or the t-con board (this is the board that "maps" the scaled signal on the screen - it's a board usually at the top of the LCD monitor under a metal shield and is permanently attached ot it via delicate ribbon cables).

How to narrow it down:
I think the best approach would be to take some voltage measurements before and after the problem occurs. These would be the 5VSB (5V standby comming from the power supply), the input and output voltages of the two regulators on the logic board (should be close to C80 and C83), and the t-con supply voltage (usually 5V or 3.3V for most monitors).

You will need a multimeter for this. All voltages should be referenced to ground (i.e. any metal part on the case of the LCD - attach negative (black) lead of the multimeter to that).

And last but not least, add pictures of your monitor!

[lostsingle]

Re: Hanns-G HG281D, LCD Monitor no power

Hi all out there!!

My HG281D does something weird ,I replaced all the caps after that is was working smooth for about 2 months .
Now the power light comes blue but no backlight .

I have take some measurements and I don't have 12v or 24v on any off the pins from the power board.

What must or can I do to repair that issue ?
Hope that you can help me !

I have al the necessary tools to measure ...esrmeter -multimeter-oscilloscope..etc

thanks in advance

Lostsingle

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

No 12V/24V can be due to bad power supply or the logic board is not sending the PS_ON to turn on the power supply.
Did you use Low ESR/IMPEDANCE type caps? Did you replace the two caps on the main board?
Please up load good clear pictures of YOUR boards.