Hanns-G HG281D, LCD Monitor no power

[slyevo]

Re: Hanns-G HG281D, LCD Monitor no power

Hi
I have this model & just recently it has started to click then the screen would go black & sound from hdmi would go off (Blue power light stays on) This would last for about 2-3 seconds then it will come back on the screen flickers for a second and it's fine until next time it does it.
I was looking at a repair kit but thought it wise to ask for a second opinion before wasting money.....
Kind regards
Mark

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

Hi
I have this model & just recently it has started to click then the screen would go black & sound from hdmi would go off (Blue power light stays on) This would last for about 2-3 seconds then it will come back on the screen flickers for a second and it's fine until next time it does it.
I was looking at a repair kit but thought it wise to ask for a second opinion before wasting money.....
Kind regards
Mark

This sounds more like a bad solder joint or other intermittent connection than a case of bad caps. The standard suggestion applies: Open it up, take one over-all picture of the cards in the monitor, and one of each card. Attach them to your next post using 'Manage Attachments' (below the text entry area).

The first point I would check is the power supply outputs. The fact that it is losing sound may indicate the main power supply is shutting down.

PlainBill

[attilahooper]

Re: Hanns-G HG281D, LCD Monitor no power

Hey folks. Great thread, thx to all the contributors.

So, Hanns G HG281D rev.1 2007 manufacture.

- started flaking a while ago, no power on issue. hit that button 5+ times to make it come on, blah blah.

-occasionally picture would flake, image shift with superimposed image, and so on.

bought lcdalternatives package of 12 caps. dunno if they're an auth vendor but here's a link. feel free to kill it:

http://lcdalternatives.auctivacommer...-P2087771.aspx

First run was a success. But then quietly failed. no more power-on, no blue light. Tried with the vga D-sub connector and still no go. Checked power switch = good.

Gonna order up C707 C603 C605 C606 from digikey. As per rec's on this thread.

1) Anyone have DK's part #'s handy ? thx in advance
2) Should I replace C114, C203, C111, C108, C203, C205 and the big honking 420V 150 mF ?

[attilahooper]

Re: Hanns-G HG281D, LCD Monitor no power

Hey folks. Great thread, thx to all the contributors.

So, Hanns G HG281D rev.1 2007 manufacture.

- started flaking a while ago, no power on issue. hit that button 5+ times to make it come on, blah blah.

-occasionally picture would flake, image shift with superimposed image, and so on.

bought lcdalternatives package of 12 caps. dunno if they're an auth vendor but here's a link. feel free to kill it:

http://lcdalternatives.auctivacommer...-P2087771.aspx

First run was a success. But then quietly failed. no more power-on, no blue light. Tried with the vga D-sub connector and still no go. Checked power switch = good.

Gonna order up C707 C603 C605 C606 from digikey. As per rec's on this thread.

1) Anyone have DK's part #'s handy ? thx in advance
2) Should I replace C114, C203, C111, C108, C203, C205 and the big honking 420V 150 mF ?

edit: did some of my own homework

C707, C603 35v 22mF - panasonic P11230-ND
http://search.digikey.com/scripts/Dk...name=P11230-ND

C606 100V 1mF - panasonic P10765-ND
http://search.digikey.com/scripts/Dk...name=P10765-ND

C605 50V 47 mF - panasonic P10321-ND
http://search.digikey.com/scripts/Dk...name=P10321-ND

^^ is this a good selection ?^^

[momaka]

Re: Hanns-G HG281D, LCD Monitor no power

^^ is this a good selection ?^^

Yup. Panasonic FC is always a fine choice for the small caps.

2) Should I replace... the big honking 420V 150 mF ?

Those very, very rarely fail. In most cases, they don't need to be replaced and are not a problem.

[attilahooper]

Re: Hanns-G HG281D, LCD Monitor no power

thx momaka. I'm gonna do C707 C603 C605 C606, since they seem to be popular amongst power issues.

[lukeinusa]

Re: Hanns-G HG281D, LCD Monitor no power

I have a similar problem: my Hannspree HF289H 28" monitor recently stopped powering on. When I plug in the monitor, the power light briefly flashes orange and then goes out. After that, the monitor will not power up.

I opened it up and removed the power circuit. Pics are below.
Having read the previous posts, my initial plan is to replace all the caps (haven't done this yet). However, the pics show that on the underside of the board, there is a lot of brown discoloration around Q601 (bottom-center of P1010603). I had to scrape away some of the brown residue just so I could read the part number. Does this mean that the transistor has shorted? Should I replace this as well as or instead of the caps?

This is my first attempt at repairing anything this complicated (done a few guitar pedal fixes) so any help would be much appreciated.

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

I have a similar problem: my Hannspree HF289H 28" monitor recently stopped powering on. When I plug in the monitor, the power light briefly flashes orange and then goes out. After that, the monitor will not power up.

I opened it up and removed the power circuit. Pics are below.
Having read the previous posts, my initial plan is to replace all the caps (haven't done this yet). However, the pics show that on the underside of the board, there is a lot of brown discoloration around Q601 (bottom-center of P1010603). I had to scrape away some of the brown residue just so I could read the part number. Does this mean that the transistor has shorted? Should I replace this as well as or instead of the caps?

This is my first attempt at repairing anything this complicated (done a few guitar pedal fixes) so any help would be much appreciated.

The brown discoloration looks more like Q601 was replaced, and the flux was not cleaned up properly.

I wouldn't replace any caps just yet. While caps can (and do) fail without any visible signs, I would expect to see some signs of bulging or overheating, but this looks remarkably good.

As a first step, I would suggest measuring the output voltages of the power supply. The voltages are labeled on the bottom of the supply.

PlainBill

[lukeinusa]

Re: Hanns-G HG281D, LCD Monitor no power

Thanks for the response PlainBill.

I bought this monitor new about 3.5yrs ago and have never opened the case until today so I don't think Q601 was replaced. I agree that the caps don't look bad (I was disappointed when I saw this as I thought it would be an easy fix). Any other ideas about what could have caused the discoloration?

I tried measuring the output voltages. To do this, I connected the power circuit to the mains output and then compared the ground to the different voltage points on the bottom left of the board, right? I measured 0V everywhere ... does this mean that something has shorted or should I start replacing caps now?

Thanks for your help.

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

Thanks for the response PlainBill.

I bought this monitor new about 3.5yrs ago and have never opened the case until today so I don't think Q601 was replaced. I agree that the caps don't look bad (I was disappointed when I saw this as I thought it would be an easy fix). Any other ideas about what could have caused the discoloration?

I tried measuring the output voltages. To do this, I connected the power circuit to the mains output and then compared the ground to the different voltage points on the bottom left of the board, right? I measured 0V everywhere ... does this mean that something has shorted or should I start replacing caps now?

Thanks for your help.

One minor correction - not all monitor subassemblies work when they come off the assembly line. It is entirely possible that it became necessary to replace Q601 before the power supply was ever installed in a monitor.

When you hook the power supply to an AC voltage only one output will be 'live' - the 5 volt standby (+5VSB) pin on the 11 pin connector at the end of the supply. If that shows 5 volts, unplug the power cord, hook up the signal card, and check the PSON pin and recheck the +5VSB pin on the same connector. Given the symptoms, I'd expect PSON to be low.

PlainBill

[lukeinusa]

Re: Hanns-G HG281D, LCD Monitor no power

+5VSB is reading OK with and without signal card. Everything else is 0 or close to it.
With signal card hooked up, you called it: I read only .06V on the PSON pin.

So does this help isolate the problem to the part of the board that supplies power to the signal card?

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

+5VSB is reading OK with and without signal card. Everything else is 0 or close to it.
With signal card hooked up, you called it: I read only .06V on the PSON pin.

So does this help isolate the problem to the part of the board that supplies power to the signal card?

Probably the reverse. This APPEARS to be a problem with the signal card. IF PSON is at or very near 0 volts with or without the signal card, the signal card is the problem. IF the signal card is the same as the one in the picture on page 1 of this thread, check the voltages on U7 and U8. One pin of U7 should read 3.3V, one of U8 should read 1.8V. If you have a different signal card, a picture of that will be necessary.

PlainBill

[lukeinusa]

Re: Hanns-G HG281D, LCD Monitor no power

My signal card is different (Hannspree HF289H). Pics are below.
I don't see anything obviously broken. Any idea which pins I should check to see where this could be failing?

Thanks for your advice.

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

My signal card is different (Hannspree HF289H). Pics are below.
I don't see anything obviously broken. Any idea which pins I should check to see where this could be failing?

Thanks for your advice.

Excellent pictures, this makes it very easy for me.

My, aren't we fancy! 2 HDMI ports, an RGB AND 3 BNC connectors.

There are four regulators, . In each case, pin 1 is identified with a white dot on the circuit board. Pin 2 is the one in the middle, and pin 3 is the last one. The tab is electrically connected to pin 2.

Hook the signal card up to the power supply. Set your DMM to the 20 VDC range. Note the position for EC910 and EC920 are empty. Use the spot closest to the white dot for the black probe. Measure the voltage on pins 1, 2, and 3 of U101, U102, U103, and U904, and report the voltages.

PlainBill

[victor20f]

Re: Hanns-G HG281D, LCD Monitor no power

Hi all, I have Hanns-G HG281D LCD monitor with no power problem.
I inspected visually all caps on PS board (PSM217-404-H-R), they are look absolutely normal. Also I tested all big semiconductors, fuses, coils, transformers and resistors. Nothing found bad so far. If some body had similar problem with this issue please help. Thanks.

Hello, I have the same problem. Attached is a picture of my starting circuit. What do you recommend?



http://es.zimagez.com/zimage/circuitoarranque.php

[outbreak]

Re: Hanns-G HG281D, LCD Monitor no power

I am having similar trouble with this board, I have already used a cap repair kit. There is no blue led in front, and there is no 5v during standby (with or without the video board).

Any help would be appreciated.

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

I am having similar trouble with this board, I have already used a cap repair kit. There is no blue led in front, and there is no 5v during standby (with or without the video board).

Any help would be appreciated.

The same thing we tell everybody else. Take good, well lit, sharp pictures of the top and bottom of the power supply board. Attach them to your next post using 'manage attachments' - below the text entry area.

Also, a brief history of the problem would be helpful.

PlainBill

[outbreak]

Re: Hanns-G HG281D, LCD Monitor no power

Unfortunately I don't have too many details about the monitor, it was going to be recycled at my job. When I first looked at the power supply there was no bulging or leaking caps that I could see, but since I found so many repair kits online I decided to give it a shot. All the blue caps are my new ones from nte.

Any input would be appreciated

Jason

[PlainBill]

Re: Hanns-G HG281D, LCD Monitor no power

Unfortunately I don't have too many details about the monitor, it was going to be recycled at my job. When I first looked at the power supply there was no bulging or leaking caps that I could see, but since I found so many repair kits online I decided to give it a shot. All the blue caps are my new ones from nte.

Any input would be appreciated

Jason

The first mistake. NTE caps are overpriced, and do not have the low ESR characteristics required for this application. At a rough guess, you could have bought the caps to completely recap this power supply for $15 - $20 (including shipping) from DigiKey.

The second mistake is some caps were not replaced. These can cause problems.

There is an 8 pin IC on the top of the board, U601. The pin in the lower left corner is pin 1, pins are numbered counter-clockwise. Using pin 1 as ground, what are the voltages on pins 2 and 5?

In the upper right corner of the picture of the bottom side of the board is the connector to the signal card. Using the bare metal around the mounting hole in the upper right corner of the board as ground, what are the voltages on each pin of that connector?

PlainBill

[outbreak]

Re: Hanns-G HG281D, LCD Monitor no power

Good to know about the caps, bought them cheap at my job so its not a big deal if they need to be replaced again. Will have to get back to you about the board readings, I don't have my meter with me right now.

Thanks for all the input

Jason