Hanns-G HG281D, LCD Monitor no power

[Greg4050]

Re: Hanns-G HG281D, LCD Monitor no power

Thank, I was only checking the file size. I borrowed this camera, so I had no idea the default was that many pixels!

Pictures NOW attached.

[Ritalin]

Re: Hanns-G HG281D, LCD Monitor no power

I had the same monitor w/ the same issue and the same power board. Couldn't get it to work. Called up Hanns-G and RMA'ed it, got a refurbished one. Took about 3 weeks, but was worth it.

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

The focus isn't too good on the picture of the power supply top, you may have to redo that. The one of the bottom is quite good.

Step 1. Put the power supply back into the monitor, fasten it in place with the screws, and hook up the AC supply. Don't hook up any other cables. Set your DMM to the 20 volt range. Use the mounting screw in the lower right corner as ground for the meter. Measure the voltage on each pin of CN1, CN2, and CN3. If you get voltage readings (I'd hope you see 5 volts on one pin), report them, then stop.

If all of them read 0, reset your DMM to the 200 volt range and CAREFULLY measure the voltage across the leads of the large cap.

PlainBill

[Greg4050]

Re: Hanns-G HG281D, LCD Monitor no power

Counting from the lower right corner, Pin 5 of CN2 is reading 5.21

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

Counting from the lower right corner, Pin 5 of CN2 is reading 5.21

We all have to start somewhere. I understand you are a Noob, and I DO make allowances. I HATE to have anything depend on an assumption. When you say that CN2, Pin 5 reads 5.21, does that mean all other pins read 0 volts?

If so, hook up the signal card (the one with the inputs) to the power supply and to the control panel. Don't bother hooking it up to the LCD panel yet. Now repeat the voltage measurements.

Next, in the upper left had corner of the signal card are two voltage regulators, U7 and U8. Again, using a mounting screw as ground, what are the voltages on all three pins of each regulator.

PlainBill

[Greg4050]

Re: Hanns-G HG281D, LCD Monitor no power

Thank you for your patience. Yes all other pins were zero.

After connecting the signal board, all other pins are still zero and pin 5 is still 5.20.

From the corner of the signal board moving to the right

Pins of U7 read 5.20, 3.32, 0
Pins of U8 read 3.32, 1.82, 0

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

Thank you for your patience. Yes all other pins were zero.

After connecting the signal board, all other pins are still zero and pin 5 is still 5.20.

From the corner of the signal board moving to the right

Pins of U7 read 5.20, 3.32, 0
Pins of U8 read 3.32, 1.82, 0

Excellent work. And bad news. Those numbers indicate the power supply is operating normally. And I was leading you off on an incorrect tangent. Sorry about that. OK, you are seeing 2 seconds to black.

First, let's make sure there are no power issues. A quick background. The power supply is a fairly common design - a standby supply which is always on, a main supply which is turned on when the monitor is on, and a PFC front end that is also turned on when the monitor is on.

In the above tests, was the power LED on? If it was, you should have seen at least one other voltage on the connectors.

Next, you seem to be missing a picture of the inverter. That is likely to be the cause of the problem.

PlainBill

[Greg4050]

Re: Hanns-G HG281D, LCD Monitor no power

I didnt have the LED hooked up earlier. With it connected, it is on. First blue, then orange.

Pin 11 of CN2 reads 0.01

I have attached 3 shots of the inverter. L, M, R for Left, Middle, and Right

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

Power off and unplug lcd for all tests below.

1) There are two SMD fuses, F1 and F2, on your inverter board. Check to see if they are good.

Details explained at (section 3)

https://www.badcaps.net/forum/showthread.php?t=10419

with posts #19 and #20

2) This is not your exact inverter transformer (section 4), but see

http://www.lcdparts.net/TransformerD...ProductID=3360

Note pins S1, S2, S3, and S4. Measure the resistance between S1 and S2. Note the reading. Do the same for S3 and S4. Repeat for all transformers on the inverter board. Report all measurements.

[Greg4050]

Re: Hanns-G HG281D, LCD Monitor no power

From those directions, the fuses appear to be good. Both read 0.7

Transformers L to R S1-S2, then S3-S4

1. 1142,1147
2. 1144,1148
3. 1161,1169
4. 1159,1167
5. 1151,1159
6. 1146,1152
7. 1156,1164

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

Transformers L to R S1-S2, then S3-S4

1. 1142,1147
2. 1144,1148
3. 1161,1169
4. 1159,1167
5. 1151,1159
6. 1146,1152
7. 1156,1164

All those readings are within (barely) 3% of each other which suggest the inverter transformer secondary windings are likely good.

1142 x 1.03 = 1176
1169 x 0.97 = 1133

Move onto the ccfl tests as explained in the troubleshooting guide.

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

If the CCFLs don't show any problems, C76 and C77 should be considered suspects, as well as the caps on the inverter supply portion of the power supply.

PlainBill

[Recycler]

Re: Hanns-G HG281D, LCD Monitor no power

Hello all,

First off, sorry to come busting in like this. This is my first post and I would like to thank PlainBill and retiredcaps for their help, you may not not know it but I've been reading your posts fore some time and learned a great deal.
I would also like to thank the rest of the members on this board and especially those who shared their experiences with this Hanns-G HG281D. It allowed me (finally) to repair my own monitor.
Please bear with me, I live in South America and English is not my native language.

Let's get down to the facts.

It all began with distortion on the screen, spikes, jiggling and shimmering. It got worse over time.
When booting the PC, the monitor would display the windows startup screen, and then go black. The led stayed blue.
Only after more than a minute the picture came back, after some jiggling and spiking it would finally stay on.
Recently, the monitor would shut down spontaneously while working with some documents or some type of pictures, guess the contrast had something to do with it.
I would then turn it of and turn it on again to restore the picture.
It would also display severe distortion on lower resolutions.
From what I saw, the backlight didn't ever fail. It was purely a video issue.

After I got fed up with the darn thing, I disassembled the monitor (stupid enough without reading here first) and went straight to the power supply, as this is nearly always the part that fails.

My monitor was manufactured in March 2009. My boards are identical of those posted by Greg4050.
I was surprised to see the power supply in perfect condition. Japanese caps (United Chemicon from what I could see) and no sign of bulging or heating.
Nevertheless, I did replace some caps only to find that it didn't make a difference.

I then used the power of Google and came here, reading some posts about the caps on the logic board failing.
I decided to disassemble the monitor again and take a close look at the logic board.
There were signs of heating near the two voltage regulators.
After looking closely at C80 and C83 I found they were "Xunda" brand "RK" series, 100uf/16 volt.
I don't trust these kind of less known brands. I did repair a lot of PCC boards and also some monitors and the failing caps were nearly always less known, mostly Chinese caps.

In my country you can forget about buying quality caps. Importing them would be possible but expensive and it takes a while.
We get all Chinese caps like Tung, "U", Jakec, VLSOM and a even some Teapo.
When I went to use some of these new-bought caps I found them bulging already after two months of storage. Utter crap!

So in this case I took a defective Intel 945 LGA775 motherboard and took the caps. They were United Chemicon also, but sadly series KMA, none of the recommended caps here.

I decided to take the risk, even if it would show some improvement then at least I could try to get better caps later on.
I was pretty sure the problem was C80 and C83 on the logic board, but didn't want to replace blindly all of them. I wanted to know which caps were causing the problem.
Finally I replaced C80 and C83 both 100uf/16V and also C13 and C14 both 10uf/25V because they were near by and probably stressed by heat already.

I'm now sitting in front of my repaired HG281D monitor, no shutting down or spiking/jiggling anymore!
The above might help people in repairing their monitor, and if you do, please post your experience.

I owe you guys a beer, if you ever come this way just drop me a line.
Cheers.

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

This is my first post and I would like to thank PlainBill and retiredcaps for their help, you may not not know it but I've been reading your posts fore some time and learned a great deal.

By view count, Troubleshooting Computer Displays is the #1 subforum here. PlainBill accounts for 20% of the posts and the majority are quality posts. And I can honestly say that the majority of what I know, I learned from his posts.

We are quite aware that anything on the Internet is read by a ton of people. Some people in this world believe information is power and hoard it. I, on the other hand, share it freely with others. Always have, and always will.

I just open you didn't read all the posts where I made mistakes!
There are a few posts where I wish I could hit the delete key!

Please bear with me, I live in South America and English is not my native language.

Your english is more than adequate and probably better than 50% of North American high school students.

So in this case I took a defective Intel 945 LGA775 motherboard and took the caps. They were United Chemicon also, but sadly series KMA, none of the recommended caps here.

Caps on the main/logic board don't experience the same amount of stress as those on the SMPS board. So don't worry too much about the KMA series.

I'm now sitting in front of my repaired HG281D monitor, no shutting down or spiking/jiggling anymore!

I owe you guys a beer, if you ever come this way just drop me a line.
Cheers.

Congrats on the repair especially if goods in your country cost a lot.

It is also neat to see people from different parts of the world where we have helped.

Thanks for sharing and confirming my suspicions about this monitor running temperature hot.

[onyx00]

Re: Hanns-G HG281D, LCD Monitor no power

I'm in a similar position to others that have posted. My monitor only has issues when it is asleep and then wakes up, or was switched off and you turn it back on.

It comes on, then starts flashing and making a popping sound, until finally doing something like changing the resolution brings it back from the dead. While this on/off flashing routine is happening, the power light stays blue on the monitor.

Hoping I can follow what has been discussed previously and fix this thing. I have a good soldering iron, just need to take the monitor apart. Might need to pick up a cheap ESR meter as well - I have a multimeter already.

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

I'm in a similar position to others that have posted. My monitor only has issues when it is asleep and then wakes up, or was switched off and you turn it back on.

It comes on, then starts flashing and making a popping sound, until finally doing something like changing the resolution brings it back from the dead. While this on/off flashing routine is happening, the power light stays blue on the monitor.

Your description sounds consistent with caps that are dry and have high ESR. As the caps warm up, the ESR drops allowing the lcd to work.

Since we have had so many reported issues with this monitor running temperature hot, I suggest you consider recapping all electrolytics caps on the power and logic board. This might cost you $20 in caps, but to save a 28 inch monitor, I think it is worth the investment.

[budm]

Re: Hanns-G HG281D, LCD Monitor no power

That is why one of the trick is use hair dryer locate bad caps in the general area.

[beauchampy]

Re: Hanns-G HG281D, LCD Monitor no power

Thought I would just add my experience to this thread (I signed up here after saving two HG281d's from impending doom).

So I had two of these. Both of them had a verrrry shaky picture and would start flicking on and off after about 10 minutes use, they were practically un-usable.

I read a few posts here and decided to go ahead and replace all of the caps on the logic board (the one with the audio and input ports), despite all the caps looking 'ok' they were all CapXon..

Since I'm in the UK I ordered from RS Components, my order looked like this..


RS Stock No. Qty Unit Price Goods Value Description
704-7895 50 £0.07 £3.60 Capacitor Al 85deg 10uF 16V 4x7
703-7490 25 £0.29 £7.20 Capacitor Al 105deg 470uF 16V 8x11.5
703-7488 50 £0.12 £5.90 Capacitor Al 105deg 100uF 16V 5x11
704-7908 50 £0.08 £3.75 Capacitor Al 85deg 100uF 16V 6.3x7


These are all Rubycon caps. These are also the smallest quantities you can buy from RS. Since I had two to fix, dropping £25 on caps was no biggie.

De soldering the caps was pretty easy, used a 60w adjustable iron, probably shouldnt have used the max temp but I work fast so it was ok. Added a bit of fresh solder to the points to get them flowing nicely then simply flicked the cap out from the other side. Used a pump to clean up the holes, voila.

So I did monitor number one and complete success. Picture is perfect, monitor has been running for hours with no problems.

Monitor two is also working just fine, except there is a green line of vertical pixels (which was there to begin with), however the shakyness and the shutting down has been remedied.

So I'm just going to do my research on the vertical line problem, then I should hopefully have two working monitors.

Great stuff, glad I found this thread! Thanks to everyone who has contributed their input.

[onyx00]

Re: Hanns-G HG281D, LCD Monitor no power

Your description sounds consistent with caps that are dry and have high ESR. As the caps warm up, the ESR drops allowing the lcd to work.

Since we have had so many reported issues with this monitor running temperature hot, I suggest you consider recapping all electrolytics caps on the power and logic board. This might cost you $20 in caps, but to save a 28 inch monitor, I think it is worth the investment.

Should I replace all caps on all boards, or just the power board? Any place I can get a list of caps for my boards as well? I figure I can then just go order from Digikey.

Probably pick up a hot air rework station as well, unless you guys think this is a minor enough job to do it without one. I have a basic, older Weller soldering station that seems to work pretty well.

[retiredcaps]

Re: Hanns-G HG281D, LCD Monitor no power

Should I replace all caps on all boards, or just the power board? Any place I can get a list of caps for my boards as well?

I have a basic, older Weller soldering station that seems to work pretty well.

I suggest both boards.

Manufacturers can and have made board revisions while keeping the same model number. Relying on someone else's cap list is like going into surgery with someone else's x-rays.

Your Weller shold suffice.