Newbie with Viewsonic VX2835WM Problem

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

Oops, I do have another question: the buttons on the front of the VX2835, like other Viewsonic models, are a bit dicey and so I avoid using them where possible to keep them functional as long as possible. So I tend to turn it on/off at the mains. Does this do the power supply any harm compared to using the power button on the front?

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

Symptom 1 probably was the power board. I think that will stay fixed.

Your symptom 2 doesn't sound like what I am used to with the HG281D (similar model). In that case the fuzziness or pixelation affects the entire screen. And it's main board. Your problem sounds a little different. It may still be main board. But it could also be T-Con or the panel.

Maybe somebody else can diagnose this problem.....

"I get an intermittent interference pattern, usually only affecting a small part of the screen. It sort of looks like a fine cross-hatching, usually at an angle but just now the cross-hatching was aligned with the screen axes, i.e. vertical & horizontal."

The one thing you can check is the voltage regulators on the main board. And those 2 big caps. (even if they were recapped years ago)
retiredcaps has a great guide on how to check voltage regulators https://www.badcaps.net/forum/showthread.php?p=261329
And Norcal has an excellent video on YouTube https://www.youtube.com/watch?v=cNFzBJELFoU

Thanks for the links, very helpful. I've rigged up a fan on the back to keep the heat down somewhat, so it doesn't go hurting itself again. Next time I get the chance to take a look, I'll do the following:

(1) check main board regulator voltages
(2) replace any faulty ones
(3) if no faulty regulators, recap the main board

Just now I need to catch up on the work that I need the monitor for, so I'm not sure when I'll do the above. At some point I'll try to get a picture of the interference and post it to see if anyone has seen anything similar ....

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

Symptom 1 probably was the power board. I think that will stay fixed.

Your symptom 2 doesn't sound like what I am used to with the HG281D (similar model). In that case the fuzziness or pixelation affects the entire screen. And it's main board. Your problem sounds a little different. It may still be main board. But it could also be T-Con or the panel.

Maybe somebody else can diagnose this problem.....

"I get an intermittent interference pattern, usually only affecting a small part of the screen. It sort of looks like a fine cross-hatching, usually at an angle but just now the cross-hatching was aligned with the screen axes, i.e. vertical & horizontal."

The one thing you can check is the voltage regulators on the main board. And those 2 big caps. (even if they were recapped years ago)
retiredcaps has a great guide on how to check voltage regulators https://www.badcaps.net/forum/showthread.php?p=261329
And Norcal has an excellent video on YouTube https://www.youtube.com/watch?v=cNFzBJELFoU

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

I figured it bridged to R223, but I wanted you to verify it first. Good job

As for your other problem it sounds like it might be the mainboard. Do you get fuzziness or some sort of distortion? I checked a picture of that mainboard posted earlier in this thread. I can see what appears to be 2 caps that are slightly bulging on the top left. The big green ones.

Hmmm, I've just given it a fairly stern test, running a movie with mostly dark scenes for more than an hour, which gets the monitor good and hot because the CCFLs are blazing away but hardly any light is escaping the front. This formerly would cause 2 symptoms:

1. at random intervals the screen would go dark for maybe 20ms. Like a very sudden spike but too short to actually see a black screen, so you would perceive a kind of dark pulse. They would be at erratic intervals sometimes a few seconds apart, sometimes minutes. The CCFLs were not causing this, they didn't show any pulsing (you can see their white output directly from the side or back when the cover is off)

This was treatable by simply opening a large window with white background on the desktop, i.e. letting heat/light out the front. However, after recapping, this problem doesn't seem to happen, suggesting it was a power-board problem (which is what it sounds like). So far, so good. I'll keep watch for it, but maybe it's cured.

2. I get an intermittent interference pattern, usually only affecting a small part of the screen. It sort of looks like a fine cross-hatching, usually at an angle but just now the cross-hatching was aligned with the screen axes, i.e. vertical & horizontal. You could call it a kind of fuzzy interference pattern I suppose.

Usually if I'm using Word etc I won't even notice this and I only see it if there is some kind of colorful background, eg a movie or picture.

So it's a minor inconvenience really. But I've always thought it was most likely a main board issue.

None of the capacitors on either the power board or the main board looked bad (no bulging or anything else that I could see). But obviously some of those on the power board were bad. The main board has already been recapped under warranty years ago. There are some notorious main-board caps (from memory, C124 and C126) that were among those recapped. But they've had time to go bad I guess, with the amount of heat back there.

Unlike all the other problems, this fuzzy pattern hasn't really gotten worse over time.

I figure that this monitor design really needs a small fan because the power board gets too hot, so my plan is to attach a fan to the back (I'll probably leave the back cover off, it's been like that for years). I tried a PC case fan a few days ago and I'd say it was too powerful, the back of the monitor was stone cold with that running. So I'll reduce the fan voltage or get a smaller fan and see how that goes.

But I'm curious if the "fuzzy interference" symptoms are familiar or suggest anything in particular ...

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

I figured it bridged to R223, but I wanted you to verify it first. Good job

As for your other problem it sounds like it might be the mainboard. Do you get fuzziness or some sort of distortion? I checked a picture of that mainboard posted earlier in this thread. I can see what appears to be 2 caps that are slightly bulging on the top left. The big green ones.

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

Result: perfection!!!!!

Monitor is up and running beautifully!!!

Well, OK, I think it will have some problems when it warms up: this monitor has been living with assorted illnesses for a long time.

BUT, for the first time in years it switched on perfectly. It's had the usual power-supply issues that were getting worse, slow and erratic switching on, various weird stuff and getting worse until it became unusable. So it's been in a corner until I had time to recap it.

I'll describe the other symptoms when I've come down off my working VX2835 high ... although as a practical matter, since they only occur when it gets warm, I could probably cure them with a fan ...

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

I've used rubber silicone for years and never had a single problem.

It's good that you stopped to ask before you made that bridge. That is a very tricky board. It actually has traces that run UNDER tiny SMD components like you see with upside down 223 and 472 resistors. 472 has 2 traces that run underneath it to JR11 and JR10. I believe your cap lead connects straight up to the upside down 223. (as you view the pic) But I'm not 100% sure. What you need to do is get some high powered magnification and look to see if that torn pad had a very small trace connecting it straight up to that 223. I just looked and found a board where the person ripped off that exact pad. I don't see a connection straight up to the 472. It looks like it went to the 223. Hope that helps

Thanks for your assistance. When I first lifted the pad (unsoldering the cap), it was left hanging on by the trace, which appeared to go to R223. Then when I soldered the new cap in, the trace broke leaving the pad completely free. The bit where the trace broke off still points to R223, like in the pictures. So that was my theory but it was pretty hard to see (I'm shortsighted, which helps a bit, but still not easy) & I thought it was worthwhile for an expert set of eyes to also have a look, so thanks for that.

I've just had another look under some strong light with some magnification and if I turn it to catch the light I can see there is a trace directly between R223 and R472. On the pictures it looks like there could be one but the light didn't pick it up and it just looks like a gap.

So I will bridge the cap to R223 ... I think the main problem will be getting it mechanically firm before soldering. I'll see how I go.

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

I've used rubber silicone for years and never had a single problem.

It's good that you stopped to ask before you made that bridge. That is a very tricky board. It actually has traces that run UNDER tiny SMD components like you see with upside down 223 and 472 resistors. 472 has 2 traces that run underneath it to JR11 and JR10. I believe your cap lead connects straight up to the upside down 223. (as you view the pic) But I'm not 100% sure. What you need to do is get some high powered magnification and look to see if that torn pad had a very small trace connecting it straight up to that 223. I just looked and found a board where the person ripped off that exact pad. I don't see a connection straight up to the 472. It looks like it went to the 223. Hope that helps

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

Hi again,

I forgot part 2 of my question. When I first started recapping the board, all the glue was a bit of a mystery. But now I realize how fragile some of the traces are and so gluing some of the caps might not be a bad idea.

I see epoxy glue mentioned. Is it OK to use silicone on circuit boards? Seems to me it has the right properties but I don't know if it can cause problems.

BTW, very impressed with your war on bad capacitors. I am happy to be joining the good fight

[MadCapR]

Re: Newbie with Viewsonic VX2835WM Problem

Hi,

I'm also recapping one of these VX2835WM power boards, and I also lifted the pads on some of the caps. I see from this thread that it's a common problem. Mostly I got them soldered OK-ish. But one pad broke completely.

I've marked it on the attached pics (these are pics from earlier in the thread, not my actual board).

It looks like I'm lucky (sorta) because it looks to me like a straightforward problem to fix, but I wanted to ask the experts here before I go putting on a solder bridge and possibly blow it up if I'm not reading the board properly (i.e. I'm not experienced at figuring out where traces go).

Any help much appreciated...

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

50v 22uf can replace 35v 22uf. Just make sure it's rated at 105c not 85c. Hopefully its a good quality cap manufacturer.

For you and others working on this board. I highly recommend practicing your soldering on an old used spare circuit board. Practice desoldering. Using the wick. Applying heat to melt solder, then removing that heat so you don't heat the pads so much they separate. Practice installing the cap in the right direction and getting a solid solder joint to the pad. Basically and hour or so spent practicing will pay off before you go the to real board "where it really counts". And watch that video on soldering I posted. Good luck!

[Supramantt]

Re: Newbie with Viewsonic VX2835WM Problem

OK. I did a continuity test to see where the leads from that cap with the lifted pads connect to. The photo shows the 3 places you will need to bridge. You can clip the metal legs from a capacitor to use as bridges.

You might want to practice on an old circuit board first. And watch that video. Soldering just takes a little practice. But once you get it; it's like riding a bike. Good luck.

Thanks for the help.
I have a bunch of 50v 22uf caps. The person who sold them to me said that the 50 would work better then the 35v that the board came with. Do you agree?

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

OK. I did a continuity test to see where the leads from that cap with the lifted pads connect to. The photo shows the 3 places you will need to bridge. You can clip the metal legs from a capacitor to use as bridges.

You might want to practice on an old circuit board first. And watch that video. Soldering just takes a little practice. But once you get it; it's like riding a bike. Good luck.

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

Good advice selldoor. Especially if he needs some glue to make those cap leads stick to the board.

Supramatt - I'm going to be repairing that same board later this evening. I'll let you know where those 2 leads connect to so you can bridge them to the component they connect to.
Till I can get back, I want you to watch this video on soldering. https://www.youtube.com/watch?v=I_NU2ruzyc4

You want to add solder to the tip of the iron, then touch the solder on the cap on the board. Then pull out. Never push back in, even slightly, because the copper pads will tear off then.

This can be repaired, but you don't want to have any more that you need to bridge because of torn pads or traces.

https://www.youtube.com/watch?v=I_NU2ruzyc4

[selldoor]

Re: Newbie with Viewsonic VX2835WM Problem

Extra blob may not help - You can however add wire support to make sure it is electrically connect. I cant really tell from the picture looks like one trace goes from one side for the ZD406 to the cap and then to R403 so just solder a piece of wire to do the same.

The other side trace looks to go from the other end of ZD406 just to the cap and actually looks close enough to just solder bridge.

If after doing that the cap is still wobbly apply some non conductive mastic or failing that epoxy glue (just a small dot) to hold the can to the board.

[Supramantt]

Re: Newbie with Viewsonic VX2835WM Problem

Darnit, the first cap pulled the trace off. The 2nd one was a 22uf 35v and the kit I received does not have one of that size in it. Not off to a good start I made very poor looking beads to hopefully touch the original traces. IDK, it might be destroyed.

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

Good deal. Please come back and let us know if it worked. **back to my birling, also known as log rolling** *splash*

[Supramantt]

Re: Newbie with Viewsonic VX2835WM Problem

I thought I recognized that board! That's the same one used in the Hanns-G 28". Due to the heat, that board tends to dry out the smaller capacitors in the middle. Try this: replace the 3 caps circled in red. And I would also replace the 5 circled in blue. See if that doesn't bring it back to life ~L-J-7~

Thank you! That will be helpful. I should have asked before so I would have only needed to order the 6 instead of the 21, but it was only 12 bucks for the 21.
Thanks again

[Lumberjack777]

Re: Newbie with Viewsonic VX2835WM Problem

ok. I think that's the same power board I posted in post #10. https://www.badcaps.net/forum/showpo...1&postcount=10

Those little caps don't bulge; they dry up on the inside. That monitor runs hot, and those little inferior quality caps dry up. If you replace the 3 circled in red it should fix the problem. You can also replace the ones circled in blue if you choose to.

Make sure when you desolder you don't push down on the capacitor. Pull straight out. Those thin copper pads lift easily. I've seen 3 botched repairs, where the guy pushed or wiggled the caps, and broke the pads and the copper traces on that board.

If you want to chance replacing ALL of the 21 caps that's your decision. But I'd replace the 3 circled in red and be done with it

[Supramantt]

Re: Newbie with Viewsonic VX2835WM Problem

I was not able to update yesterday, but i got it apart finally. It really did not want to separate. 3 of the 4 tabs broke during the teardown. I do not see any bad caps but one that might be bad. I purchased a kit for the 21 caps, it should be here soon and then I will re solder them together.