Viewsonic VA800 with rolling lines

[hulla]

I acquired a Viewsonic VA800 LCD monitor that works but has rolling horizontal lines. Looks like interference on a television. It is not as bad at 75 hertz and is most prominent at 60 hertz. Weird thing is that I don't get the rolling lines when the computer is off and I get a "no signal" display. Also, display is fine during "power on self test" on one computer but not on another computer. Once Windows is on screen, I get the rolling lines.

It is not my video card or computer since other monitors work. I checked that the cables are seated tightly.

I searched google and found that the 1 uf capacitors tend to be bad so I replaced all 5. But no change.

Any ideas?

[hulla]

Re: Viewsonic VA800 with rolling lines

I never say any bulging caps. The caps I replaced are the metal ones. I'll try to attach a photo of the board.

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

I never say any bulging caps. The caps I replaced are the metal ones. I'll try to attach a photo of the board.

What did you use for replacement?
Any problem on the PSU?

[hulla]

Re: Viewsonic VA800 with rolling lines

I got the caps from Radio Shack. I know you guys don't like them, but I was impatient. I initially used 4.7 uf since that is all I could find but then swithced them out for 1 uf 35 volt. Didn't make any difference.

This monitor uses an external power supply which I just bought on ebay.

[xtraelectronics]

Re: Viewsonic VA800 with rolling lines

I had a monitor with an external PSU. It did not work properly. (Can't remember the exact symptons, but yours sounds familiar.) However, using the bench supply, it worked fine. After figuring out how open the original PSU, I discovered several bulged caps in there! Replacing them, and adding a missing thermistor (the board had a jumper across where the thermistor was supposed to be). The PSU is and has been working perfectly for several months now.

[lucky13]

Re: Viewsonic VA800 with rolling lines

I got the caps from Radio Shack. I know you guys don't like them, but I was impatient. I initially used 4.7 uf since that is all I could find but then swithced them out for 1 uf 35 volt. Didn't make any difference.

This monitor uses an external power supply which I just bought on ebay.

Can you post a pix of the external power supply? Also, a close up pix of the rating tag would be useful.

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

I got the caps from Radio Shack. I know you guys don't like them, but I was impatient.

It is not that we don't like them, it is that they don't like the applications normally discussed around here ....

This monitor uses an external power supply which I just bought on ebay.

Sorry if I was not very clear. I repaired one like a month ago that was dead, and the dead part was the 12v 5A PSU with an output of 12v, then 11,then 10, then 12, then 11, then.... well, you get the idea. Opening it revealed a small bulging cap that would be the equivalent or the small cap that makes PSU/Inv voltage output oscillate. Replaced it and the unit was recovered from the dead state it was .
More or less what xtraelectronics told in post #4, just a different (but similar) case ..

[hulla]

Re: Viewsonic VA800 with rolling lines

Here is a pic of the external power supply. It is brand new from ebay. My wife picked up the monitor from a garage sale without the power supply so I had to get one. The prior owner described the same problem but I actually tried to fix it before ordering the new power supply so didn't see for myself.

I also have a picture of the what the screen looks like. It is hard to see in the photo though. You can best see the lines by the "My Yahoo" bar near the top.

I also have a photo of the opened monitor. Let me know if you need closeups of any part of it.

[lucky13]

Re: Viewsonic VA800 with rolling lines

How did you determined that the external power adaptor need to be 12V/5A? Was there a label at the back of the monitor that indicated that?

Do you have access to a bench p/s that can put out pure 12v 5A dc?

It is just a possibility that the monitor is power hungry and your ebay p/s has too much ripple when pulling 5A.

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

How did you determined that the external power adaptor need to be 12V/5A? Was there a label at the back of the monitor that indicated that?

If that was for me, I just picked up a 12v 5A as I have previous experience with 18" needing either that or 4.16A. If it was for him, he didn't mention the amp rating of his brick.

Hulla, why don't you post the link of the brick you brought?

[hulla]

Re: Viewsonic VA800 with rolling lines

It says 12V 5amp on the back of my monitor.

I don't have a bench p/s. I have an old computer p/s that will supply 12v though. But not sure of the best way to connect it up.

Here is a link to the brick I got.

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

If it was for him, he didn't mention the amp rating of his brick.

My bad. The 2nd picture "says" it....

I just receive a 18" unit (NEC) that does something similar. It uses 24v 2.4a input and it is using a 24v 2.3 amp PSU/brick.
Nothing wrong visually except for that .1a difference.
I had to adapt this PSU for the unit. It was bought untested and the owner didn't want to spend 30+ on a PSU for a dead monitor, so we went that way to see if it turned on or not. Now that it turns on, she still doesn't want to spend if that "failure" is not caused by the brick.
I heard some "stories" about getting 24v out of an ATX PSU. Anyone had done this before? I'm going to start another thread about this but I posted here because it is the same failure.

[shadow]

Re: Viewsonic VA800 with rolling lines

I heard some "stories" about getting 24v out of an ATX PSU. Anyone had done this before?

You can get 24V out of an ATX power supply by connecting the load (the monitor) between the 12V and the -12V rails. The potential difference will be 24V.

However this is not recommended because of the low current rating of the -12V line. Not to mention, some modern power supplies do not have a -12V line.

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

You can get 24V out of an ATX power supply by connecting the load (the monitor) between the 12V and the -12V rails. The potential difference will be 24V.

However this is not recommended because of the low current rating of the -12V line. Not to mention, some modern power supplies do not have a -12V line.

I just read that I'll need an AT PSU for that almost for sure. What would be the amp rate for that configuration, if (let's suppose) the 12v amp rate is 6a?

[kc8adu]

Re: Viewsonic VA800 with rolling lines

i have repaired several of this series of viewsonic.
you need to replace all the surface mount lytics.

[hulla]

Re: Viewsonic VA800 with rolling lines

I just found a way to connect a spare computer p/s to the monitor and got the same rolling lines problem.

[hulla]

Re: Viewsonic VA800 with rolling lines

i have repaired several of this series of viewsonic.
you need to replace all the surface mount lytics.

ouch. ALL of them? Desoldering these is kinda tough for me. I'm using a 15 watt soldering iron.

These are the surface mount beer can ones right?

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

I'm using a 15 watt soldering iron.

Better Toasty does not find out about this. He didn't stand my initial 20w iron... I don't wanna know what he'll think of your 15w .....

[shadow]

Re: Viewsonic VA800 with rolling lines

I just read that I'll need an AT PSU for that almost for sure. What would be the amp rate for that configuration, if (let's suppose) the 12v amp rate is 6a?

On a junk Hairong unit that I have lying around. It claims that it can handle 0.5A on the -12V rail and 10A on the 12V rail. When you are using the 24V output (from -12V to +12V rails). Current will flow from the +12V rail to the -12V rail. However the maximum current that the -12V rail can handle is 0.5A. If you draw more current, the -12V voltage rail may fail. Even thou the +12V rail will be perfectly fine with the load.

[EGuevarae]

Re: Viewsonic VA800 with rolling lines

On a junk Hairong unit that I have lying around. It claims that it can handle 0.5A on the -12V rail and 10A on the 12V rail. When you are using the 24V output (from -12V to +12V rails). Current will flow from the +12V rail to the -12V rail. However the maximum current that the -12V rail can handle is 0.5A. If you draw more current, the -12V voltage rail may fail. Even thou the +12V rail will be perfectly fine with the load.

Case closed. I need at least 2.4 (3 would be great) amps, so I'm out of luck.