Bad Viewsonic LCD monitor

[zocoloco]

Hi all,

My Viewsonic VP201b monitor has recently started to mess with me, and I would like to get some advise what to check, since I believe there are lots of people who know LCDs more than me. I'm working with electronics, so the handling and possibly repairing should be no problem. I just need an idea where to start. Since I'm a little low on money, I would really need to fix the monitor, can't afford a new one at this point.

I have also tried desperately to find a service manual for the monitor without success. The viewsonic store has no in stock, and the net seems to be empty in this particular matter. Anyone with schematics or service manual is very welcome to contact me.

The problem is this: The monitor mostly starts up OK, but after a while the right half of the screen starts to flicker. Sometimes it goes back to normal after a little while, sometimes it ends up in vertical lines that cover the area. Lately, the problem has also started to appear on most parts of the left side of the monitor, so soon I have nowhere to go... Please check the image link below for a photo of the monitor.

I'm very thankful for any feedback on this.

Thanx.

http://img92.*************/my.php?image=dsc07584qp9.jpg

[willawake]

Re: Bad Viewsonic LCD monitor

post a naked photo of the pcbs

[arneson]

Re: Bad Viewsonic LCD monitor

You will be taking it apart to get a picture so while your in there,
reseat the clean and reseat the connectors between the video card and the screen drivers on the panel.
It your lucky the problem connections are there and not on the ribbons embedded to the glass.

[arneson]

Re: Bad Viewsonic LCD monitor

You will be taking it apart to get a picture so while your in there,
clean and reseat the connectors between the video card and the screen drivers on the panel.
It your lucky the problem connections are there and not on the ribbons embedded to the glass.

[zocoloco]

Re: Bad Viewsonic LCD monitor

post a naked photo of the pcbs

and with pcbs you mean...the circuit boards inside the monitor?

[zocoloco]

Re: Bad Viewsonic LCD monitor

You will be taking it apart to get a picture so while your in there,
reseat the clean and reseat the connectors between the video card and the screen drivers on the panel.
It your lucky the problem connections are there and not on the ribbons embedded to the glass.

So you think the problem might be in the connection between the circuit boards and the panel?

[arneson]

Re: Bad Viewsonic LCD monitor

You hope that's what it is.
Look in there Very closely for a spill, and it goes without saying to examine every electrolytic for signs of bulging.
Then reassemble and put a plug in it.

[zocoloco]

Re: Bad Viewsonic LCD monitor

Update:

Sometimes, when the screen flickers but is still watchable, when I play a movie (xvid), the movie is perfect, but the surrounding area is not. Is this a clue to you experienced lcd repair people?

Still didn't open it up though...

Edit: Can som Mod please move this thread to the appropriate section, just noticed I started the thread in the wrong one...thx!

[zocoloco]

Re: Bad Viewsonic LCD monitor

Hi y'all again. Finally managed to open the thing up. Didn't see any obvious signs (for me that is) of what the problem could be. The only thing that struck me was this white powder in the power supply section, is this normal?

See attached pictures and let me know if you find anything weird on them.

Thx all!

[EGuevarae]

Re: Bad Viewsonic LCD monitor

Hi y'all again. Finally managed to open the thing up. Didn't see any obvious signs (for me that is) of what the problem could be. The only thing that struck me was this white powder in the power supply section, is this normal?

See attached pictures and let me know if you find anything weird on them.

Thx all!

I personally use a VP201b and have two VP211b with cracked screens (one of them with a bad inverter, and I have not checked it since the screen is broken anyway), and none of them had that powder. FYI, the PSU and inverter are exactly the same between them. The lamps I don't know, but the controller/VBoard is different (20.1" --> 21.1").
If you need pictures, I can post them. I have the boards around here.

[zocoloco]

Re: Bad Viewsonic LCD monitor

I've looked a little more into this and it seems that the powder comes from the thermal paste applied to the transistor marked in the image below. Is this a normal reaction of thermal paste? Is it from heat, or what do you think?

[EGuevarae]

Re: Bad Viewsonic LCD monitor

Looks like we have the same monitor, yet different inner components.
Look at the pics of my PSU. It has only two "big, fat" caps (1000uf 35v).
Also, the transistor layout is different. As you can see, I don't have the "white powder" problem. Look at the pics. I think that the connector referred early in the thread is the one I marked in both your boar and mine. I've seen that problem on Dells (E171FP) and Proviews (716s/776s - My wife is using one of those "loose connector" kind of monitor, and so far, no problems in two months), and even on a Polaroid 19"LCD I got on eBay that "had bad image" and ended up just being a remove and reseat op on that ribbon.
Maybe if you remove, inspect (clean) & reseat the ribbon, your problem will be gone.
Not too much connectors to check either:

• DC input from PSU
• I/O from USB daughterboard (in your case. My board does not have that card as a separate one)
• I/O from front panel controls (narrow flat ribbon to the right)
• Inverter I/O
• LCD Panel I/O (Wide flat ribbon, on the left)

The left ribbon might be the culprit.

[zocoloco]

Re: Bad Viewsonic LCD monitor

To me it looks like we have the exact same layout, the only thing with your pics is that they are taken from different angles, or? And that your big capacitor is hidden under some kind of plastic cover...

[EGuevarae]

Re: Bad Viewsonic LCD monitor

If you are talking of the big fat cap on its side (the one with the wiped powder ot the top), It is the input cap, and mine has it, as you said, covered in plastic. But I notice a small difference in the boards (besides yours being a Delta L20C-2 and mine being a Delta ADP-60BF A). In my case, I have two 1000uf 35v caps, then an inductor, and your board looks as if it has three 1000uf 35v. Also, the layout of the main board is different, regarding the USB hub portion mainly. Just a note because they are the same model but different on the inside. As for size, they look to be interchangeable with either my PSU or my Main Board.
Did you try to remove and re seat the ribbon?

[zocoloco]

Re: Bad Viewsonic LCD monitor

Tried to reseat all connectors, without much success. I am tending more and more to believe that the problem lies within the power supply of the screen. The "white powder" is probably thermal paste that has "burst out" due to extreme heat on the transistor pointed out in my picture above. The only question is why it has become hot...

Found a spare power supply online for 30$. The shipping to Sweden, where I'm living, is 40$ though. Have to think about it a little, cause it might still be that the problem is in another part of it, and spending 70$ without reason seems a little stupid then...

[EGuevarae]

Re: Bad Viewsonic LCD monitor

I am tending more and more to believe that the problem lies within the power supply of the screen.

Have you measured the V output of the Power supply? There are two cables for ground and another two for V that go from the PSU to the main PCB board.
I'll look up my notes (or even better, measure it from my VP201 if possible) and let you know the values. Also, if you PM you full address I can ask on the Post Office the shipping cost from USA 92254 (CA, where I am) to your place, and I can ship the PSU for you to test if it is not that much (I'm kind of broke right now...)

[zocoloco]

Re: Bad Viewsonic LCD monitor

Have you measured the V output of the Power supply? There are two cables for ground and another two for V that go from the PSU to the main PCB board.

No, I didn't, but it's not impossible that it gives the correct voltages. If you check the picture in my first post, you can see that the screen is working, it just has some intermittent glitches/stripes. I am more thinking that this "superhot" transistor or some other component in the PSU is damaged and therefore distorts the picture every now and then.

Of course, the problem could also lie somewhere else, what makes me wonder quite a lot is that the problem always comes on either the left or the right half of the screen, or sometimes both or sometimes nowhere. This might of course indicate that there is in fact something on the main board or so that causes the problem...just can't get my thoughts of that transistor which got so incredibly hot.

I'll look up my notes (or even better, measure it from my VP201 if possible) and let you know the values. Also, if you PM you full address I can ask on the Post Office the shipping cost from USA 92254 (CA, where I am) to your place, and I can ship the PSU for you to test if it is not that much (I'm kind of broke right now...)

Sounds excellent if you wouldn't mind. I'll PM my address details, so you can at least look it up. If it's not that much I could as well perhaps buy the PSU and send it to you, and you forward it to me? Anyway, if it's 40$ shipping in all circumstances, it might not be worth it. I'm actually not that wealthy atm myself, because of my move (I'll explain in PM).

[EGuevarae]

Re: Bad Viewsonic LCD monitor

Crazy Idea.
How difficult and expensive would be for you to get your hands on a 18v 3.5/4 amps adapter?
That is the PSU's output to the main. You could inject the voltage from the adapter to the board and see what happens. You would not exceed the V needed for the board, and provide the 3.33amps needed. Someone around here correct me if this is a bad idea.

[PlainBill]

Re: Bad Viewsonic LCD monitor

I've been fighting with the 21" version of this monitor (VP211b). It was a freebie I picked up locally, probably a discard by a company upgrading their computers.

The initial symptom was a black screen; the power LED would turn green if hooked up to a working computer, but the display was black. When I opened it up I noticed a white deposit on the back of the case above the power supply. It looked a little like frost. After a LOT of struggling (I hadn't found this site yet) I discovered that F1 on the inverter board had blown. Replacing it brought up a stable display, so it gets hooked up to a computer for an extended run.

Just as I was patting myself on the back (about half an hour later) I notice the display is jumping side to side - only one or two pixels, but ??? After another 10 minutes it has gone completely - breaking up so the top half of the display is on the bottom, the 'No signal on DVI-D' icon is appearing and disappearing, etc.

When I found this thread the 'substitute power supply' idea triggered what few remaining brain cells I retain. Through perfectly legitimate channels I have a Kensington 120 Watt portable power supply. And with the N3 tip it puts out 18 volts.

The monitor has been working well for the past 2.5 hours. It is very stable on both analog and digital inputs. SO now it's time to figure out what is going wrong with the power supply.

One curious thing I noted. Initially I tested it without any signal input. The current drain (from the Kensington) was .88A with the 'no signal' icon on screen, .18A when it went into standby. I just checked again and it's drawing 2.45A with the DVI input active. Is there any chance this is due to the CCFLs dying of old age?

Thanks for any suggestions; this is a great site.

PlainBill

[EGuevarae]

Re: Bad Viewsonic LCD monitor

I've been fighting with the 21" version of this monitor (VP211b). It was a freebie I picked up locally, probably a discard by a company upgrading their computers.

The initial symptom was a black screen; the power LED would turn green if hooked up to a working computer, but the display was black. When I opened it up I noticed a white deposit on the back of the case above the power supply. It looked a little like frost. After a LOT of struggling (I hadn't found this site yet) I discovered that F1 on the inverter board had blown. Replacing it brought up a stable display, so it gets hooked up to a computer for an extended run.

Just as I was patting myself on the back (about half an hour later) I notice the display is jumping side to side - only one or two pixels, but ??? After another 10 minutes it has gone completely - breaking up so the top half of the display is on the bottom, the 'No signal on DVI-D' icon is appearing and disappearing, etc.

When I found this thread the 'substitute power supply' idea triggered what few remaining brain cells I retain. Through perfectly legitimate channels I have a Kensington 120 Watt portable power supply. And with the N3 tip it puts out 18 volts.

The monitor has been working well for the past 2.5 hours. It is very stable on both analog and digital inputs. SO now it's time to figure out what is going wrong with the power supply.

One curious thing I noted. Initially I tested it without any signal input. The current drain (from the Kensington) was .88A with the 'no signal' icon on screen, .18A when it went into standby. I just checked again and it's drawing 2.45A with the DVI input active. Is there any chance this is due to the CCFLs dying of old age?

Thanks for any suggestions; this is a great site.

PlainBill

I guess that is normal for a monitor that size. I'm using one of those to view this thread (a VP201b like the one of this thread, not a VP211b. I have two units of that model with a broken screen....). My best guess is that your PSU has a problem (due to the fact that you are using external power and so far, so good). I can't remember what caps did my own VP had when I received it, but I replaced them (2 1000uf 25v caps) and it's been like three month of continual (almost) use, and nothing has gone wrong. Have you checked the V output of your PSU, or replaced any caps in there?
What caps do the PSU have?