VP201b Heat-Related Screen-Half Flake Out

[Zymoticus]

I have a problem with a VP201b similar to that of Zocoloco's, posted elsewhere on this forum, but the behavior is a little different. For reference, I bought the monitor sometime around 2005 and it's worked perfectly up until 5-6 months ago:

When I turn on the monitor it runs fine until it starts to warm up - generally from 4-6 minutes. Then one or the other half of the screen, divided exactly down the middle, will first start to flicker, then waver in kind of an "underwater" appearance, then deteriorate into vertical blocks and lines in the general colors of whatever's on the screen at the time, until the entire side is that way. After a little while that side will black out altogether. If I power the unit off and back on again, the affected side will invariably show up as vertical b/w stripes, as in the last photos.

Eventually the remaining half will follow suit with the same symptoms.

If I leave the monitor running for another ten minutes or so the halves will wink back to life and occasionally even go back to perfect, only to flicker and flake out again.

I have a series of photos that illustrate the problem, the first three from a PC that just died, the remainder from a new one I bought to replace it. I'm hoping it's ok to put up a whole gob of photos - if not let me know.
























Thanks for any insight you can offer.

[EGuevarae]

Re: VP201b Heat-Related Screen-Half Flake Out

I'm hoping it's ok to put up a whole gob of photos - if not let me know.

Welcome.
Open the unit and post pics of the power supply.

[Zymoticus]

VP201b P/S pix

Excuse the lengthy absence - I replaced it with a new monitor shortly after posting, and just haven't had time to open up the unit until now. So finally, some pix of the power supply, and one of the adjacent board, 'cause I'm wondering if that white stuff is epoxy that's supposed to be there, or crap that's leaked out of something:
















Please let me know if there are any other areas I should shoot.

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

I have a VP201b with exactly the same problem, except that it only affects the left half of the screen. I have the same power supply, and there are no visually apparent problems with any components.

The output voltage of the PSU under load is 17.70v. Individual bulb voltages measure (from the small return wires to ground):3.14, 2.96, 3.13, 3.00. The brown caps are all Taicons and the blue ones are Nichicons.

I also have another broken VP201b that I could take some parts from, although i think that one has a short somewhere because it draws the PSU voltage down to ~2.0v, however it is 17.85v no load.

Any ideas?

[lucky13]

Re: VP201b Heat-Related Screen-Half Flake Out

Remove the Main board (green one) and wash off that brown, yucky stuff on the solder side. Also, gently remove the flat cable that is connected to the LCD and reset it. I would remove that yellow tape they used to tape down the cable. From what I've seen, the tape is putting too much stress in pulling the cable AWAY from the connector. I leave the flat cable floating (instead of securing to the back of the LCD panel).

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

I did originally have that brown stuff on the back of the main board, and cleaning it off didn't seem to make any difference. However, after reseating the LCD end of the ribbon cable I only saw a brief glitch so far (it lasted less than a second) in a couple of hours of running the monitor. I haven't put the case back together yet, as I am planning to replace a few capacitors tonight, but I'll report back in a couple of days and let you know how everything went.

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

Sorry for the double post, but I'm not sure how to edit my previous message. Anyway, I got all the capacitors replaced with Panasonics (except the big one on the psu) but now it looks like the vertical refresh rate is messed up. I did forget to insulate part of the back of the inverter board where I cut away the plastic so I could solder in new caps, so it could be shorting or arcing to the frame; looks like I'll be cracking it open again tonight.

I also discovered that the only problem my parts monitor has now is with the mainboard (when I turn it on, the power led blinks orange a few times then turns off, but it works with my other mainboard); are mainboards available for the vp201 anywhere, or should I sell that one off as parts?

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

Well, I swapped in a different inverter and I now have the same problem I did in the beginning. I know it's not loose cables, bad electrolytics, the inverter, or an individual ccfl. My guess is either the logic board or the panel itself has problems. Next i'm going to move the logic board and the inverter over to my "parts" panel and see what happens.

[jankro]

Re: VP201b Heat-Related Screen-Half Flake Out

You mentioned that you have another VP201?

If so try swapping the panel from that unit to this, or the pcb's from this "half display" unit to the spare display.

What I'm getting at is that this similar problem is with Dell 2001FP and it uses the same panel as this Viewsonic and I solved the problem by swapping the panel from a different display and now the Dell works fine because the problem was with the panel, not with the displays PCB's.

-Jan

[bluto]

Re: VP201b Heat-Related Screen-Half Flake Out

Hopefully this is not too off topic, but I have a VP201b that I wouldn't mind selling for parts. It works completely fine. I got it as non-functional and re-capped it to make it work, but it has a pretty decent pressure mark on the screen. So other than the pressure marked screen, all of the parts are in great condition. Here is the the thread where I have the pictures of the innards: https://www.badcaps.net/forum/showpo...7&postcount=19

PM if you are interested.

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

Since I replaced the inverter I have not had this monitor apart again. Right after the inverter replacement it had the same issues for a couple of days as it originally had, however recently it has not shown any signs of trouble, even during heavy use. I am puzzled; maybe it was a loose connection or something, but how could it improve by just being used more? I'll be hanging on to my parts monitor, of course, but for now I'm going to leave things as they are.

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

Well, wouldn't you know it - as soon as I was confident that the problem was better, it came back. Tonight (hopefully) I am going to move the electronics over to my other panel, and I will report back if that fixes it.

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

I finally got around to placing the inverter and logic board from my original monitor into the one I got used from ebay, and so far it has not had any problems.

My only complaint is that the LCD from ebay is very dark and tinted brown. I've tried to find information about what is causing the darkness/brownness, but all that I've come up with is a brief mention of needing to replace the diffuser paper. Well, I didn't know LCDs had diffuser paper, but anyway, I'll probably leave it how it is.

In summary, the problems pictured at the beginning of this thread were, in my case, caused by something within the panel - not the logic board, inverter, or power supply.

[lucky13]

Re: VP201b Heat-Related Screen-Half Flake Out

dtruax,

The part likely gone is the T-con board (the PCB on the top of your screen underneath the metal shield).

Yes every LCD panel has a diffuser inside (to evenly distribute the light from the lamps). Some of these develop a brownish/yellowish spot/patch and cannot be removed.

You can of course disassemble both panels and swap the clean/clear one from your dud panel but that is a huge risk if you have never done it before (not to mention dust spots get left behind inside the panel when you open them up).

[dtruax]

Re: VP201b Heat-Related Screen-Half Flake Out

lucky13,

Thanks for the info, it makes a lot of sense now why there is a diffuser - for some reason it didn't occur to me that the back light needs to be diffused. Is the T-con board possibly replaceable, or are they generally permanently attached?

[lucky13]

Re: VP201b Heat-Related Screen-Half Flake Out

Generally, only on a large screen size (>26" ?) then the manufacturer will consider the use of a T-Con board. For small monitors, it is permanently attached to the screen via several flat thin cables (typically on the top). These flat cables are attached to the screen but can easily be torn apart or detached. So, it is not for the faint of heart (I torn at least 2 in my past).

There are two layers between the lcd screen (outer surface) and the back side of the module. One is a clear diffuser and the other is like a one-way mirror film. Provided they are the same panel, you can swap them around but be VERY CAREFUL. Of course, dust is a big issue so do have a can og compressed air to blow out dust caught between the layers. Afterall, you are working with used panels and there are dust hiding in the gaps.

[qufighter]

Re: VP201b Heat-Related Screen-Half Flake Out

I'm having the same problem with mine. It's about an inch in on the left side of the screen until about half way across the screen after about 25 minutes of use.

http://www.youtube.com/watch?v=rwnTlMtDABA

The PSU caps seem fine, I suspected something on the mainboard. In addtion to the brown crust on the side of the board (they all seem to have this crust) Several of the small 47uf surface mount caps seem to have leaked something and also the 470uf in the top right corner of the board. I ordered some replacements. Nothing looks odd on the t-con or backlight board. I tried a different board however the problem remained identical.