Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

What is this part? (LCD Monitor PSU part)

Status
Not open for further replies.

Wobble

New Member
Hello everyone. I'm new here. Hopefully I'm going about asking this question properly.

A friends monitor stopped working. It turns on but won't stay on. Theres this part that looks like a motor that appears burnt or something.

**broken link removed**
**broken link removed**

Is it indeed broken? If so, where can I find another one. And is it an easy job to fix? Thank you.
 
It is a transformer. It does look burned. You cannot get another one. Transformers usually do not burn out by them selves. Probably there is also a diode that burned out first.
 
It is a transformer. It does look burned. You cannot get another one. Transformers usually do not burn out by them selves. Probably there is also a diode that burned out first.

Are you saying it can't be fixed? I'd also like to add that the idiot kept his monitor on like 24/7 and like never turned it off. That can't be good for it. I can't take a transformer out of another device? I thought I've seen pics of computer PSUs with a similar looking thing inside. Although I'm sure they are not all the same.
 
If you had a second monitor or power supply from that monitor then......
Each power supply will have a different transformer.
Computer power supplies are different.
 
The trafo looks dodgy, but to be honest, it could easily be just the laquer coating that is naff and bubbled with heat. If the monitor is coming on at all it's unlikely to be faulty as it will almost certainly be supplying more than one power rail. I would be looking at discreet components like capcitors, diodes and resistors for failure.

The computer power supply being used to repair a monitor is novel, but to be honest, modern monitors can use all manner of supply rails besides 5 & 12V. He was just lucky in this case.

Either get a service manual for the monitor and properly measure the supply rail voltages etc or obtain a replacement power supply for it.
 
The trafo looks dodgy, but to be honest, it could easily be just the laquer coating that is naff and bubbled with heat. If the monitor is coming on at all it's unlikely to be faulty as it will almost certainly be supplying more than one power rail. I would be looking at discreet components like capcitors, diodes and resistors for failure.

The computer power supply being used to repair a monitor is novel, but to be honest, modern monitors can use all manner of supply rails besides 5 & 12V. He was just lucky in this case.

Either get a service manual for the monitor and properly measure the supply rail voltages etc or obtain a replacement power supply for it.

They say when the tops of the capacitors are bulging, that means its bad. Well how flat should they be. In this lighting/angle, you can see how some capacitors appear very slightly curved on top opposed to 100% flat.

**broken link removed**
**broken link removed**
 
if it powers up but won't stay on, it's probably not the power supply, but something else, like the backlight inverter, which will be another board that looks similar to a power supply, but has some plugs going to the panel. these regularly cause the symptoms you are describing... there may also be something wrong with one of the supplies on the board you have been showing pictures of (there are actually 3 supplies on this board. the standby supply, running off the small transformer center bottom, and two other supplies, running off the medium size transfomer bottom right, and the big transformer mid center (the one you thought might be burned)). i would look at the inverter board first. the caps you showed on this power supply look ok. bulging tops means that the tops looked like they popped open, and there's usually fuzz or bits of paper sticking out of the top too. none of the tops of the caps you showed are bulged, and the heat sensitive paint/ink on the tops of them are all still yellow, not black.
 
Last edited:
The transformer looks cooked but may have survived. There seems to be a leaking electrolytic cap bottom right of the pic in post #1.
 
The transformer looks cooked but may have survived. There seems to be a leaking electrolytic cap bottom right of the pic in post #1.

lol. No. I know what your talking about. That is an optical illusion. That thing is actually flat and pushed to the right a little. It looks more like a flat magnet and that grease on it is thermal paste I believe. It was resting up against a big metal covering.

I will look at the actual monitor more when I get a chance. This part is the only thing I have in my house right now.

I've heard about backlights going bad. If thats the problem, I'm supposed to still see a picture if I hold a flashlight up to the screen, right?
 
I've heard about backlights going bad. If thats the problem, I'm supposed to still see a picture if I hold a flashlight up to the screen, right?

If it were only the lamp that had failed and assuming that the inverter did not shut down the main control board. The trouble is, some do, and some don't.

That thing is actually flat and pushed to the right a little. It looks more like a flat magnet and that grease on it is thermal paste I believe.

That thing is the main Bridge Rectifier(bottom right). You are correct, it is covered in thermal paste.

What is the make/ model number of the monitor?
Also describe in precise detail exactly what the fault symptoms are, cos so far we are all guessing at what is happening.
Does the power light come on then go off/ change colour etc?
 
@wobble,
your initial info is yet not proper.
you can indicate make, size and model number of the monitor. Simply discussing across a photo alone, would end up only wasting site's space. however www.eserviceinfo.com has many makes of monitors' service diagrams that can be of some help to you.
once you have a relevant service manual, things would appear easier, perhaps. as the photo shows , the electrolytics appear OK even the smudging on the left of the transformer as I see the photo, could be varnish coating. unless you smell a burnt smell. Perhaps you need to distinguish between burnt smell and varnished transformer smell.
 
Last edited:
That transformer is a high voltage transformer. Using for backlight fluorescent lambs. I had a monitor (19 inch dell) first was going on and 2 -3 seconds later was going to off. I thought bad caps. i changed all but problem was continue. Later i thought any bad resistors or transsitor or diods. I checked all smd resistors, tr and other coudnt find any problem. Finally i found ..that was old back light fluorescent. Because flamans sides was almost was black. The inverter controller ic OZ9938 controlling connected fluorescents. if bad fluorescent or no connected fluorescents going to stop working. maybe your inverter ic is also same. probably bad or old fluorescents. check first black flamans at the right and left. good lucks.
 
OK, so the monitor is a 28" Hanss-G HG281D.

What happens is, I push the button, then the "No Signal" message comes up, then it goes away after just a few seconds. Then the blue power light goes off. Then it comes on again, then eventually the "No Signal" message comes back. And that just seems to repeat

Until...

I plug it into this computer. Then it seems to stabilize and stay on and work properly. But when I unplug the VGA cable from the computer, it shuts right off. And its hard to get started at all after that.

So what could this be? Its as if the monitor is getting some power from the VGA cable. Like just enough to help it out and stay on. Thats probably not the way things work, but it sure seems like it.

Oh, and when I shut it off by hand, it won't go back on when I press it again. It can take a while before I can get it fired up again.
 
Last edited:
Wobble,

Monitors normally do not work when not connected to a good signal! (this is power saving)
"No Signal" then shuts off. This is normal.
Plus in the VGA cable and it starts working again. This is normal.
There is a very tinny amount of power in the VGA cable, not enough to run the monitor, just enough to power a memory chip so the computer can read what type of monitor it is.

I just checked my monitor and it does what you said.
 
Wobble,

Monitors normally do not work when not connected to a good signal! (this is power saving)
"No Signal" then shuts off. This is normal.
Plus in the VGA cable and it starts working again. This is normal.
There is a very tinny amount of power in the VGA cable, not enough to run the monitor, just enough to power a memory chip so the computer can read what type of monitor it is.

I just checked my monitor and it does what you said.


I just checked my desktop and 19" LCD downstairs and when I pull out the VGA, the monitor goes immediately to sleep mode. Green power light turns to Yellow. It pops back on again (and turns to Green) when I put the VGA plug back in. I turn it off and it goes off. I turn it on and it comes back on.

This 28" Hanns-G monitor isn't right. It USED to just stay ON (Blue led) and display a constant "No signal" message when the computer was off or disconnected.

Now it has problems powering on. It goes on and off, on and off. No Yellow light, no standby. Now when I shut off the monitor, I can't get it to go back on. That is certainly not normal. It takes a couple minutes before it will go on again when I press the button.

EDIT: Ok, yeah, and it has problems going into standby when I tell windows to put it to sleep after a certain amount of time. It said "No Signal" with the Blue led, then it turned Yellow for a second, then off. When I wiggled the mouse, it wouldn't come back on. Remember, its connected to a netbook, so BOTH screens went black at the proper time but only this netbook's screen came back on when I moved the mouse.

Come to think of it, I wonder if this monitor was screwed up from day 1. I noticed this guys monitor (when it was at his house) slways used to say "No Signal" with the Blue power led on when his computer was off. Its like it never properly went to sleep. And now we have these issues with it not powering on

EDIT 2: I couldn't get it back on at all after putting it to "sleep". Even after waiting 10 minutes. I pulled out the wall power cord and put it back and when I pressed the button, it came on immediately. Its like I had to clear the monitors memory ok knowing that its supposed to be sleeping.

I heard theres a thing called a logic board and that can be a problem with monitors. I have no idea what a logic board looks like but I'm wondering if thats the problem. Its like the computer has the power to power on and stay on but is too stupid to know what to do. Not very "logical"...
 
Last edited:
I have a Samsung Netbook that acts oddly when using some external monitors, and requires all sorts of faffing about when using a specific 19" Dell panel that I have with it. Every one of the panels I have tried with it have power up/ standby issues and often require me to unplug it/ power cycle them etc before they are finally recognised and external video displayed. I have yet to use any external monitor with it that behaves what I would call "normally". I have put this down to the graphics chip implementation/ bios in the Netbook as all of the panels I have work perfectly on my desktop and server machines.

With all that being said, it does sound like your problem could be a backlight issue, however I would check the panel on a known good VGA source before getting any further involved.
 
I have a Samsung Netbook that acts oddly when using some external monitors, and requires all sorts of faffing about when using a specific 19" Dell panel that I have with it. Every one of the panels I have tried with it have power up/ standby issues and often require me to unplug it/ power cycle them etc before they are finally recognised and external video displayed. I have yet to use any external monitor with it that behaves what I would call "normally". I have put this down to the graphics chip implementation/ bios in the Netbook as all of the panels I have work perfectly on my desktop and server machines.

With all that being said, it does sound like your problem could be a backlight issue, however I would check the panel on a known good VGA source before getting any further involved.


I will try it with the desktop computer tomorrow. But I know something is wrong with this thing. How would you explain someone who had this thing for a few years suddenly telling me that it doesn't work and buying a new one. I will also check this out connected to an xbox 360.
 
Ok. With the HDMI the screen stays on and displays "No hdmi connection" or something and stays on. Monitor says "No vga input" or something when the VGA is pulled and the screen powers off and on over and over.

I have trouble getting the monitor started again after turning it off.


My SOLUTION:

I will just no longer turn it off using the button. I will connect it to a cheap $2 power strip and use the power strip switch to turn it on/off. I noticed when I unplug it while its on and plug it back in again, the monitor comes right on. It remembers that the power button has been pressed even after unplugging it. So thats a good thing.

So my solution is to just turn it on/off using a power strip. A pretty stupid solution, but it works. I just keep reminding myself that this 28" monitor was FREE, so I can't complain. Beggars can't be choosy. One of the things I was thinking of doing anyway was making a racing setup (I like racing games) and putting a monitor like this in front of a real car seat with a wheel and pedals. Everybodys happy!
 
i would do an ESR test of the electrolytics on the main pcb and the inverter boards. chances are you have several that are marginal, making proper operation thermally dependent and somewhat erratic.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top