Hanns-G HG281D, LCD Monitor no power

[outbreak]

On the IC labeled u601 I got 11.5v out of pin 2, and between 163.2, and 164.2 out of pin 5.
The only pin on the output connectors that has voltage is the 5vsb, it gets 4.97v. Last time I checked the 5vsb I didn't get a reading, but I did find a place on the board where a trace to a capacitor came up. The trace was very short so i was able to just jumper it with solder.
I am going to test the monitor again tonight to see if that trace fixes anything.

Thanks again for any help.
Jason

[outbreak]

Unfortunately the monitor still does nothing. No blue led, and no video.

Jason

[PlainBill]

Originally Posted by outbreak

Unfortunately the monitor still does nothing. No blue led, and no video.

Jason

This type of power supply actually contains 2 supplies - the standby supply, which is always on whenever the monitor is plugged in, and the main supply which is turned on by one of the processors on the signal card. The first question is "Is the signal card turning on the main supply". The second question is "Is the power supply processing the 'on' command.

I've marked up the picture of the bottom of the power supply. The area circled in black is the ground, the area in red is the control voltage. The first test is simple. Set your DMM to the 20 volt DC range. Hook the power supply to the signal card, and plug in the AC cord. Press the 'power' button slowly several times. Does the voltage on the control pin change? If it does, measure the voltage across the very large filter cap.

PlainBill

[a1guitarman]

Hi.. my first post and I expect out-of-place... but.. I don't know where to post this question.. >> any recommendations for a decent cap tester??

[PlainBill]

Originally Posted by a1guitarman

Hi.. my first post and I expect out-of-place... but.. I don't know where to post this question.. >> any recommendations for a decent cap tester??

Welcome to badcaps.net, and yes, it is out of place. Perhaps a mod will move it to the Test Equipment Usage, Techniques, and Reviews forum.

There are two parameters that are important - total capacitance, and ESR. When dealing with bad caps, an ESR meter is more important than something that only indicates capacitance. Many DMMs have a capacitance range; some actually have a useful capacitance range. Mine doesn't.

You will have to buy a specialized mater to test ESR. The two most popular are the Bob Parker Blue ESR meter, and the ESR-Micro 4.0.

I built the Blue ESR meter from a kit several years ago, and it works well - after I got the parts that were missing from the kit.

The ESR-Micro has received very good reviews, there MAY be an availability problem on it. The last time I checked, it was available here. That was several months ago. From my point of view, it's chief drawback is it can easily disappear on a messy workbench.

PlainBill

[onegoodpcguy]

i did this repair of the caps on the vga/hdmi imput board.

the monitor now turns on and then turns right off.

it used to turn on and have the fuzzy problem. now it turns on and back off.

it seams like the top left corner is a bit dim, but it only stays on for 2seconds max.

the light stays blue.
i didnt replace ANY caps on the power supply.
i DId replace ALL the caps on the controller board
(small hg281 board) and the inverter board (the 4 270uf 35v) ones.

[Tyradius]

plainbill
Let me recite my usual spiel. This APPEARS to be a case of 'two seconds to black'. Two seconds to black can be caused by bad capacitors, a bad transformer, bad CCFLs or the wiring to the CCFLs, or a bad component in the protection circuit.

Im sure he will tell you the same thing he told me above

On that note I believe c603,c606 and c707 on the psu were ones people had the most trouble with. Maybe start there?

I am not an expert like others on here, just what I have read when trying to fix mine.

Good luck!

[onegoodpcguy]

Originally Posted by Tyradius

Im sure he will tell you the same thing he told me above

On that note I believe c603,c606 and c707 on the psu were ones people had the most trouble with. Maybe start there?

I am not an expert like others on here, just what I have read when trying to fix mine.

Good luck!

thats a good place to start thanks.

i just find it wierd that it would stay on before the repair... and now it wont...

every other cap was changed..

ill give it a shot though. thank you.

[onegoodpcguy]

Originally Posted by Tyradius

Im sure he will tell you the same thing he told me above

On that note I believe c603,c606 and c707 on the psu were ones people had the most trouble with. Maybe start there?

I am not an expert like others on here, just what I have read when trying to fix mine.

Good luck!

my power supply board doesnt have any c606 c603 or c707
it has cs21-cs27 and c8,c34,c31,c32,c33

im going to replace them all i suppose.

[PlainBill]

Originally Posted by onegoodpcguy

my power supply board doesnt have any c606 c603 or c707
it has cs21-cs27 and c8,c34,c31,c32,c33

im going to replace them all i suppose.

That is why we ask for pictures. Some manufacturers use several different power supplies on any given model.

PlainBill

[cody_hb85]

In search of a solution to the screen flickering, no power issue I've been having with my hanns g hg281d I came across this site. So I have been reading this thread and after everything is all said and done, I have gone ahead and completely replaced EVERY cap on my power supply with caps from Digi-Key. The blue light comes on now and stays on, goes into standby when no input is plugged in, comes back from standby and recognizes the input device when plugged in. Disply works, back light come on, everything is fine...... until...... the screen starts to get fuzzy, especially around desktop icons and dialog boxes. I've also read in this thread that it could possibly be the caps on the logic board? Please advise me on where to start! I will post whatever pictures you may need as soon as I get home from work this evening. Thanks in advance!

[outbreak]

Today I replaced the rest of the caps on the power supply board I started a while back. Originally I replaced most of the larger caps with NTE brand caps from my job before I knew the ESR rating was important. Now the monitor gives me a blue on led and shows video for a second before it goes black. Before working on it today the monitor displayed no video and had no blue power on led. The NTE caps are still on the board, could the ESR rating be causing the issue?

I also noticed that the new panasonic 400v 22uf seemed to be making noise. I tried putting the old one back in just for kicks and it brought the monitor back to displaying nothing with no blue power on led.

Appreciate any info.
Jason

[PlainBill]

Originally Posted by outbreak

Today I replaced the rest of the caps on the power supply board I started a while back. Originally I replaced most of the larger caps with NTE brand caps from my job before I knew the ESR rating was important. Now the monitor gives me a blue on led and shows video for a second before it goes black. Before working on it today the monitor displayed no video and had no blue power on led. The NTE caps are still on the board, could the ESR rating be causing the issue?

I also noticed that the new panasonic 400v 22uf seemed to be making noise. I tried putting the old one back in just for kicks and it brought the monitor back to displaying nothing with no blue power on led.

Appreciate any info.
Jason

Simple answer - there have been several cases where someone used general purpose (not low ESR) caps to recap a power supply and wound up with 'two seconds to black' - the problem you are now having. Replace every NTE cap you used with Panasonic FM series. What series Panasonic cap did you use for the 22µF 400V? That capacitance seems unusually low. I expect to see something in the 80 - 150 µF range.

PlainBill

[outbreak]

The panasonic cap is EEUEE2G220, it is an EE series. Its not the main power cap on the board, it is the next largest one.

Thanks for the quick response.
Jason

[jeffery6803]

i know this post is old but wanted to add one more voice in thanking the OP for his advise replacing those 3 caps got monitor back working but i have interference in the form of wavy lines and snow at top of screen gets better longer monitor is on i think i am going to have to replace more caps to fix this but replacing 3 caps OP said made dead monitor work again so thanks

[PlainBill]

Originally Posted by jeffery6803

i know this post is old but wanted to add one more voice in thanking the OP for his advise replacing those 3 caps got monitor back working but i have interference in the form of wavy lines and snow at top of screen gets better longer monitor is on i think i am going to have to replace more caps to fix this but replacing 3 caps OP said made dead monitor work again so thanks

Sooner or later most people discover that replacing ALL the capacitors (with the possible exception of the 450 volt one) avoids a lot of grief.

PlainBill

[dullishpage]

I have the tall tail signs of this problem started to happen on a customers monitor model HG281D. The monitor will power on and work fine, but after it is on standby power mode, or turn off with ac wall power going into for several hours, the darn thing wont power on. It was start powering on, and the Blue led in the front corner will come on and then go off, then the monitor goes out, and pressing the power button several times does nothing. It is not until unplugging the power cord and trying to turn it on again will it power back on normal. I am going to order up capacitors for the psu board and try replacing them all. I don't want to mess around trying to replace a few here or there, I'm just going to replace them all and then try testing to see If i can reproduce the problem again. Although it would be nice to have a esr meter.

[jeffery6803]

it wasn`t until i recapped both the psu (no power) and then the three large 16 v 470 uf on logic card with 25 v 470 uf did i fix the 2 second black problem monitor has been working great since i plan on recapping entire logic card but couldn`t wait so used what i had until rest of caps can be delivered i tried radio shack LOL because of my impatience but their selection of capacitors was small enough to fit in a matchbox seems to be nowhere to get parts except through the mail for repairs

[dullishpage]

Originally Posted by jeffery6803

it wasn`t until i recapped both the psu (no power) and then the three large 16 v 470 uf on logic card with 25 v 470 uf did i fix the 2 second black problem monitor has been working great since i plan on recapping entire logic card but couldn`t wait so used what i had until rest of caps can be delivered i tried radio shack LOL because of my impatience but their selection of capacitors was small enough to fit in a matchbox seems to be nowhere to get parts except through the mail for repairs

If you live in the Bay Area, there is Jameco, they have will call.

[dullishpage]

I re-caped the psu board, except for the big one. Seems to have solved the issue as far as I can tell, I told the customer that if he experiences problems again, we'll redo the logic board.