Hanns-G HZ281HPB Black Screen

[nickhog]

From my Original post
"I have a HZ281 with opposite problem. My screen is black. Was working fine, selected a new web page, screen went black. Power light comes on and off with power switch, Power light turns green with either a VGA or DVI video source connected but screen stays black. No visible of bad caps, no burnt components or boards. Any thoughts or suggestions appreciated.."

My pictures aren't as good as those posted in the White Screen thread. Looks to me that most of my boards are the same as those. Hopefully you can help me identify what each board is and where to find test points...

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

Sure would like to get my eyes on a set of schematics for this monitor...

[momaka]

Re: Hanns-G HZ281HPB Black Screen

Might be an inverter/backlights issue.

Try this: turn the monitor OFF and input a signal to the monitor (such as a desktop background from your PC). When you turn on the monitor, do you briefly see the desktop flash? If not, do you see the monitor faintly flash at all? (You may have to try this in a semi-dark room.

If the answer is 'No' to the above two questions, put a bright flashlight against the LCD screen while the monitor is turned ON with an input signal. Can you see a faint image of the input signal on the screen?

Finally, I also see what appears to be several fuses (dark red rectangular boxes) on the power supply board (they have board designators "Fxxx", where xxx is a 3-digit number.) One of them is probably for the inverter and may be bad. If you can post more close-up shots of this picture yhen I might be able to tell you which ones they are:
https://www.badcaps.net/forum/attach...1&d=1451696713

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

No flicker/flash and I don't see any image with the flashlight. It's a bright sunny day here so I'll double check this in the dark tonight. Fuses are;

F720 = 5A/250v
F211 = 4A/250v
F220 = 5A/250v

All measure good in the circuit with Ohm meter. Didn't do any voltage checks because I can't get to the bottom of the board with the pink wired connectors connected.

I do appreciate your time. Would love to save this monitor since I can't replace it. Everything today is wide screen format and nothing with the vertical height of this monitor... At least nothing under $1000.

Pictures Uploaded

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

Re-checked for flicker/flash and did flashlight test in dark. No flicker/flash and no video visible under flashlight..

[momaka]

Re: Hanns-G HZ281HPB Black Screen

Re-checked for flicker/flash and did flashlight test in dark. No flicker/flash and no video visible under flashlight..

Okay, since the fuses tested fine, then it's time to roll our sleeves and dig in deeper.
You will need a multimeter for this again.

Let's start by checking the voltages on connector CN201. All voltages will be with respect to ground, which is also connected to monitor chassis. So you can connect the black (-) probe on your multimeter to monitor chassis.

Plug in the monitor, but keep it turned OFF from the power button, then carefully measure the voltages on all pins of CN201. (You can skip the ground pins, as they will have 0 Volts on them. They are labeled "GND".)
Post what results you get.

Now with the monitor plugged in, turn ON the monitor and input a signal from your PC (such as PC displaying desktop background). Again, carefully measure all of the voltages on connector CN201.
Post what results you get.

-----------------
Some technical information about your monitor power supply and the voltages you might get (just putting this here if you or anyone else is interested in reading it.)
...
Your monitor power supply actually has two power supplies inside: standby (labeled "+5VSB", pin 4 on connector CN201) and main supply (labeled "+5V" and "+12V", pins 5 and 6 for the former and pins 9 and 10 for the latter).

When the monitor is plugged in but turned OFF, only the +5VSB standby supply should be active, so you should see about 5 Volts on that pin. At this point, the voltage on pin 2, "PS(ON)", will likely be 0V. Likewise, the voltages on pins 11 and 12 will probably be 0V as well. I can't read the designator for pin 12, but it is probably an ON/OFF signal for the inverter/backlights. Pin 11 appears to be labeled "ADJ" from what I can see - this basically controls the backlight brightness of your screen when it is turned ON.

Now once the monitor is turned ON, PS(ON) will probably become 3.3-5V to signal the main supply (+5V and +12V) to turn ON, after which you should also see a voltage on pins 11 and 12 to signal the inverter/backlights to turn ON.

Anyways, I will stop here for now. Hopefully some if it makes sense. Let me know what results you get for the above voltages I asked for.

Would love to save this monitor since I can't replace it. Everything today is wide screen format and nothing with the vertical height of this monitor... At least nothing under $1000.

Yeah, I am no fan of wide screen LCDs either - not for work or daily desktop use anyways. Large (19"+) 5:4 LCDs are nice and always worth saving.

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

I follow the tech info very clearly... Great info... You are correct about pin 4, it is labeled ADJ. Here's what I got (only checked DC volts)..

Plugged in, power off:
only pins with voltage are ;
Pin 4 = 5.2v
Pin 11 = 3.12v

Power ON, Video input'
Pin 2 =5.04V
Pin 4 = 5.18v
Pin 5 = 0.69v
Pin 6 = 0.69v
Pin 9 = 0v
Pin 10 = 0v
Pin 11 = 2.95v
Pin 12 = 5.0v

So, looks like we're telling it to turn but it ain't listening...

[momaka]

Re: Hanns-G HZ281HPB Black Screen

So, looks like we're telling it to turn but it ain't listening...

Yes. Either that, or the main supply has a fault and refuses to start to prevent itself from disaster.

So probably a good idea to check the output rectifiers on the secondary side for the main supply, which would be diodes D210 and diode D220(?). That would be the TO-220 devices that are mounted on the heatsinks HS201 and HS202. You can see them on this picture:
https://www.badcaps.net/forum/attach...7&d=1452185948

With your multimeter, check resistance between middle pin of each diode and ground. Do this with the monitor UNPLUGGED. (Actually, always unplug the monitor when measuring resistance.)

I think rectifier D210 is for the 12V supply. As a test, you can also try removing fuse F211 to see if the 5V and 12V supplies will appear at the pins on connector CN201. Removing fuse F211 simply disconnects the 12V supply from the inveter. That way, if the inverter is faulty, it won't bring the whole main supply down.
Therefore, if you remove fuse F211 and you do get 5V and 12V at CN201, then we know the problem is likely the inverter. Otherwise, we continue troubleshooting the main supply in the PSU.

[budm]

Re: Hanns-G HZ281HPB Black Screen

Do you have close to 400VDC between the two legs of the main filter cap rated at 450VDC laying on it side when the monitor is turned on?
Also what are the dcv between the two legs of the two small brown filter caps laying on the side near the inverter transformer? They probably show 0VDC (should be around 24vdc, it is 28" monitor so the inverter circuit will need 24V, it is just a 28" TV without Tuner) since you are not getting the 12V for the main board either. Without the 12V you will not have the DCV to run the T-CON board so you will see anything on the screen.
BTW, please retake straight shot pictures of the top and bottom side of the power supply board, they are not quite well focused for me to see the traces and components.
The switched 12V and the 24v are generated by the biggest transformer (I cannot read the designator) on the board and the circuit that drives that transformer needs the boosted Voltage to function.

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

budm, will try to get some better pictures later tonight or tomorrow.

Meantime, momaka, I pulled fuse, no change. Fulled d-210, d-220, d-720

d210 = mbr10100ct = dual diode common cathode - one side shorted
d220 = mbr20450tg =not marked checks like dual diode and OK
d720 = mbr2060ct = dual diode common cathode - checks OK

For starters, looks like I need a MBR10100CT....

[momaka]

Re: Hanns-G HZ281HPB Black Screen

Meantime, momaka, I pulled fuse, no change. Fulled d-210, d-220, d-720

d210 = mbr10100ct = dual diode common cathode - one side shorted
d220 = mbr20450tg =not marked checks like dual diode and OK
d720 = mbr2060ct = dual diode common cathode - checks OK

For starters, looks like I need a MBR10100CT....

Yup, that shorted MBR10100CT could be it.

The replacement doesn't have to be exactly the same part. You just need to match the current rating and make sure the diode is of the schottky type. Don't use Fast Recovery (FR) diodes here, because they tend to have a higher forward voltage drop, so the monitor will run hotter - and that's not good. As for the reverse/blocking voltage rating - that needs to be in the ballpark only, since the main supply uses single transistor forward (STF) topology. The MBR10100CT is rated for 100 Volts, but 60-100 Volts will certainly do. In many cases, you may even go as low as 45V without trouble.

Do you have any spare PC junk power supplies lying around? Something like an MBR2045CT or STPS2045CT or similar might work quite well.

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

Well, I had couple old PC supplies but I just recently cleaned up... You know that that goes... Save it and you'll never need it, throw it away and you'll need it tomorrow.. Looks like about 45 cents for the diode and $6.00 shipping... I'll get one asap and get back with you on the results...

Thanks again for hangin with me....

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

Welllll, Welcome back Badcaps...!!!!

momaka and budm,
You can put another notch in your guns... Thanks to your help and suggestions, I'm sitting here looking at my beloved Hanns-G again. It was D210. Replaced it and now all is fine again. I hope this thread helps others who want to save a monitor...

Thanks again... Have one on me....


nickhog out......

[momaka]

Re: Hanns-G HZ281HPB Black Screen

Good job and glad to hear it is working again. Enjoy!

By the way, what did you end up using as a replacement for D210? New MBR10100CT?

[nickhog]

Re: Hanns-G HZ281HPB Black Screen

Since I had recently tossed out all my old PC powersupplies, I had to resort to buying a diode . I used a new MBR10100CT and, with no place to buy locally, I had to order it. 45 cents for the diode and $6 for shipping... I got 2 just in case... So, Once again... Have one on me and thanks for your support...

[momaka]

Re: Hanns-G HZ281HPB Black Screen

Hehe, that's not too bad. One time I bought a video card on eBay for $0.01. Shipping was around $8, though

So, Once again... Have one on me

Thanks, I will

[bloodzknight]

Re: Hanns-G HZ281HPB Black Screen

Hey, I read most of this and found out that the solution to your problem was a faulty diode.

I was given a (broken) Hanns-G 28 in HZ281HPB monitor today for free. Considering it's not a bad monitor, I am looking to fix it.

I believe that I am encountering the same issues as you, in the sense that there is no backlight/display won't turn on, although power is fully functional.

Being extremely new to this stuff, I'm not sure how to go about fixing the monitor or even figuring out what is wrong with it.

Any help would be greatly appreciated!

Thanks in advance,
Bloodzknight