Hanns-g HG281DJ stuck on self test after changing caps

[waigy]

I had similar problems to user "usbdevice" in the hanns g mega thread here :
https://www.badcaps.net/forum/showth...=11329&page=18

It was taking longer and longer for the monitor to warm up (only up to about 5 or 10 minutes), but once it was warmed up it would work perfect all day.
I could trick it into warming up quicker by pressing ctrl/alt/del and keeping the windows task manager window open.

So I was taking a gamble when I decided to take it apart.
I tried changing C80 and C83 as advised by a few people, I found a few 100u 16V caps in a sound blaster live.
I know they are not great caps, but I thought I would try them first to see what happened.

Since then all I get is the screen changing from one solid colour to another eg. red 2 seconds, blue 2 seconds.
But I found out by accident that the monitor does the same thing if both C80 and C83 are not fitted.
So I reckon I'm not managing to solder the caps in properly.
I've tried lots of times now putting different caps in (I have 4 from the sound blaster) and the originals.

I can usually fix anything, though I'm not a trained electrician.
I was going to buy one of the repair kits, but I reckon it would be too big a job for me with my equipment.
Does any one sell complete boards with decent caps or would any of the badcap members consider the repair if I posted the board?

[selldoor]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Are you trying it with a known source (working pc not in standby) Some monitors
default to the self test when they cant find a source - check cable from pc.
Please update your profile with country and mains voltage

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Yes the source is fine.
I have another monitor plugged in, when I switch on the hanns-g my other monitor switches off.
Normally if there was a graphics source problem the sreen would display "signal out of range" or similar.
I can't get any text on screen including the hanns-g on screen menus.

[selldoor]

Re: Hanns-g HG281DJ stuck on self test after changing caps

What does it do when connected as sole monitor using the cable connected to the other monitor. Do you have a multimeter.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

It does the same when it's the main monitor.
I have a multimeter, but I would prefer to look for a replacement board rather than making this into a marathon research and repair session.
I know the repair kit would fix it, but just changing those two caps was tricky enough.

[selldoor]

Re: Hanns-g HG281DJ stuck on self test after changing caps

ok I have just skimmed parts of the big thread and if your ps board has the original caps, most of them will probably need replacing.
Only thoughts on a replacement board would be that if it has not had the caps replaced they may well need replacing soon. Also the problem could be with the ps board or the logic board or both. If you cant get boards post pictures as in post3 of that big thread and do the checks as listed by retiredcaps.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Replacement main boards seem to be impossible to find for these.
I've spent ages searching and only found suppliers in the USA who are out of stock.

Anybody fancy a wee winter project replacing the usual suspect caps on my main board with decent caps?

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

I hope I'm not breaking the forum rules by asking another member to repair this for me.
Can some one let me know if I am.

I'm just going round in circles taking out the caps removing the solder and resoldering them, but I don't have the best of equipment and I've already lifted one trace a bit so I'm not going to do any more on it myself.

Out of all the times I've resoldered the caps I reckon I must have got a good connection at some point, so I reckon the problem could be something else now.

[selldoor]

Re: Hanns-g HG281DJ stuck on self test after changing caps

You could try posting decent pictures to see if we can see anything wrong.
The caps from the SB may not be good - what make /series - for a power supply they need to be good quality low esr.
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Hi selldoor

Thanks for answering again, it seems that I am going to have to try and repair this as it has been impossible to find parts online and by contacting hanns-g direct.
There are a few sites in USA selling the main board for 22 dollars which would be great but they are all out of stock.
I've contacted them all to ask if they are getting it back in stock.

So far I have only tried to change 2 caps but I haven't had any success doing that as I only have a soldering iron (no solder sucker etc.).
I have lifted one of the traces slightly so the thought of changing lots of caps is making me think I will just ruin the board.

The soundblaster caps have this on them :
wincap r85sm(m) -40 to 85 degrees c 100u 16v

I will take photos very soon and upload them.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Here are the pics, I should be able to get them slightly sharper when the sun comes up tomorrow.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Measurements taken when switched on and hdmi connected to pc with the monitor doing the self test thing.

The huge capacitor on the power board.
400v

CN7 starting with the black wire :
2.73v
-.002
4.95v
4.95v
-.002
12.17

CN5
brown 4.91v
black 4.91v

CN4 and 3
Red wire first
4.74v
-.002
-.002
0.6v
0.99v
1v
1.64v
0.94v
0.6v
0.96v
0.96v
1.66v
0.97v

C80 and c83 with original caps soldered back in
measured with multimeter black cable on earth

c80 3.17v
c83 1.59v

All of the caps on both boards look fine and no fluctuating measuments.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Other symtoms.
When I plug my video camera into the hdmi port, I get the same results as connecting the pc.
The monitor power light changes from amber to blue, but it only ever shows the self test thing eg. solid colours for 2 seconds each.
It will stay like that for ages, I thought maybe leaving it on like that for a long time might change things once it was proeprly warmed up, but no.

The solid colours look perfect with no bad pixels or off colour patches, it just isn't showing any input eg. text, images or on screen menus.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Can anyone see any problems with the voltage readings and images I have posted?

I'm going to buy a solder sucker or braid and attempt to change all 20 caps on the main board, though I'm not too confident about it.

[selldoor]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Ok - Have you tried connecting it via the vga socket?

On the Main board I would replace the original 2 caps and
close by them there look what appear to be 2 voltage regulators U7 and U8. One looks like it may be 1.8 v and the other 3.3v but cant be sure.
Look at this guide:
https://www.badcaps.net/forum/showthread.php?p=261329
and test the regulators.
Looking at the list of voltages it is hard to tell though
I would guess the 400v is ok with PFC the 12 volt looks ok
but all the low valtages are on the low side 5v 3.3v and 1.8v are common. If the 3.3and 1.8 are derived from the 5v then it follows if that is low they all will be. After reading retiredcaps guide see if you can find any other regulators ( one for the 5v ) and test them. If it outputting less than 5v it may not be faulty - it could be an adjacent capacitor pulling it down.
Use a 40watt iron if you have it and use solder with lead
in it - the unleaded is sometimes difficult. You will also need some flux even If you are using solder with flux in, it sometimes dries out.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Hi selldoor thanks again

I have tried the vga socket, it gets the same results.
I will order the caps/solder braid later today so I will have a few days wait where I can do more testing/measuring etc.
Even if the caps are not the fault I'm assuming that it's still a good idea to have them all replaced with high quality caps?

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Here is my caps shopping list (main board only)

12 of 10uf 25v 4x7mm 105c
5 of 100uf 16v 5x11 105c
3 of 470uf 16v 8x11.5 105c

When I search for these on the Farnell site I get up to 10 to choose from.
Can somebody recommend the best ones to go for out of the 3 caps?

470uf

100uf

10uf

Also, do you think their cheapest desoldering gun would do the trick?
I don't intend trying to impress the ladies with my desoldering gun so the size/quality isn't important to me (I'm also skint).

Recommended braid?
I only intend buying what I might need for this job only.

[waigy]

Re: Hanns-g HG281DJ stuck on self test after changing caps

I just got a good close up pic (the second one) of the area that I have attacked.
The U7 voltage regulator solder is brown and crusty looking, it was like that before I touched the board (honest guv, I have a pic to prove it).
I later got some solder on the rear side of U7 which I had to heat to remove, so I could well have fried it.

Here are the measurements from left to right as you look at the images.
Taken with the monitor on standby (orange led).

U8
0.01 - 0.08
0.01 - 0.08
3.25 - 3.30

U7
0.01 - 0.06
3.26 - 3.31
4.86 - 5.06

I couldn't find these regulators in the data sheet search, so I can't check if the measurements are ok.

[budm]

Re: Hanns-g HG281DJ stuck on self test after changing caps

U8 ia a 1.8V (You can see the V18S printed next to it) fixed 1117 series LDO regulator, it is bad!
U7 is 3.3V (You can see the V33S printed next to it) fixed regulator. It is OK.


1117 series LDO SOT-223 case style from DIGIKEY:

Adjustable:
http://www.digikey.com/product-detai...SCT-ND/1967218

1.5V fixed:
http://www.digikey.com/product-detai...SCT-ND/2121241


1.8V fixed:
http://www.digikey.com/product-detai...SCT-ND/1967216


2.5V fixed:
http://www.digikey.com/product-detai...SCT-ND/2121243


3.3V fixed:
http://www.digikey.com/product-detai...OSCT-ND/660708

This is the way to figure out if the adjustable regulator is good or not:
Notes: we are looking at the regulator with the Big tab up (the big tab is tied internally to the center pin).
Adjustable regulator will have two resistors attached to it, one resistor (Rfb) is between pin1 and pin2, another resistor (Rg) is between pin1 and ground. Pin3 is an input pin.
The voltage between the Adjust pin (left pin) and the center pin (Pin2, output) will always be 1.25V +/- 2% (this is the precision voltage reference), if it is not, it is bad.
To figure out what the output voltage should be: measure the voltage between pin 1 and ground and add 1.25V to that number, that is the output voltage on pin 2 but you have to make sure you do have 1.25 between pin 1 and 2 as noted above

[selldoor]

Re: Hanns-g HG281DJ stuck on self test after changing caps

Hi Budm - completely missed the board descriptions whilst trying to read the
writing on the components-
The links you posted are not working?

Edit - They are now.



@Waigy - I have some 1.8 vrs - if you have difficulty finding them pm me.