20" MVA worth repairing?

[blanketyblank]

I think the inverter on my LCD monitor is finally gone for good since the screen keeps flickering no matter how long I leave it on. Before that the flickering would stop after a while and I could use the monitor normally. It's a nice 1600 x 1200 panel with an MVA screen, but I'm not sure if it's worth the trouble and expense of repairing.
I think I can probably take it apart myself, but I'm not sure where to get a replacement part or if I could do it. Anyone done this before and know how difficult the process is and how much/where to buy a replacement part?

 

[SparkyJJO]

It may be the filter capacitors, which are a cheap and easy fix. The way I see it, no harm in taking it apart and taking a peek. Just be careful of the many plastic clips and short wires they tend to use.

 

[blanketyblank]

I've taken it apart, but fortunately or unfortunately I don't see any obvious signs of damage to the capacitors. I don't have any meters or anything, but the components don't look burnt. Here are the pics I took:

http://img13.imageshack.us/i/pict0030eg.jpg/
http://img59.imageshack.us/i/pict0029by.jpg/
http://img707.imageshack.us/i/pict0028a.jpg/

I was googling LCD repair and saw some vids about replacing CCFLs with LEDs. I'm wondering how well that would work since it would save me the trouble of doing this ever again when say the backlight dies. I'm worried there would be stripes or it would be too bright or something though.

 

[SparkyJJO]

On the power input/LCD inverter board, What is the make of the caps? What series?

If they are Samxon GF series, replace them. It looks like maybe one has a slight bulge in it, not sure, hard to tell on the pic. Looking at the lower-right one.

The two on the top right are the backlight filter caps.

BTW, I've had caps start failing internally and not show it outside. What can also happen is the caps were just large enough to work. But as they aged, their capacitance started to diminish, allowing for more ripple currents to go through, which can create a backlight flicker.

 

[blanketyblank]

you're right the green capacitors on the bottom of that pic say Samxon 10 V 470 microF GF(M) while the small black ones above that are Samxon 25V 220 micro F KM(M) and the large black one on the left says Samxon 25V 470 microF KF Vent.
Should I replace all of them or just the GFs?

btw is NTE a good brand? My local Fry's seems to use that brand, but I don't mind ordering online somewhere and waiting for delivery.

 

[Schmide]

Could it not just be failing cold cathodes?

 

[Rebel44]

I had same problem with my 24" MVA and I paid something like 30€ to have it repaired.

 

[SparkyJJO]

you're right the green capacitors on the bottom of that pic say Samxon 10 V 470 microF GF(M) while the small black ones above that are Samxon 25V 220 micro F KM(M) and the large black one on the left says Samxon 25V 470 microF KF Vent.
Should I replace all of them or just the GFs?

btw is NTE a good brand? My local Fry's seems to use that brand, but I don't mind ordering online somewhere and waiting for delivery.

No don't get NTE. Go to digikey.com and get Panasonic FM or FC series.

I'd replace all the Samxons on there. I think the KF/KM series aren't so great either.. Samxon makes some good ones but those aren't.

Could it not just be failing cold cathodes?

Could be, yes. But caps are much cheaper and easier to replace. Replacing a bulb is a huge pain to do. Been there, done that on a laptop screen. That wasn't fun at all D:

 

[blanketyblank]

Thanks just ordered the capacitors. Hopefully replacing them will work.
Does it matter what kind of solder you use? I think the one I have right now is a lead solder. Would there be any problem just using that or do I need something else?

 

[SparkyJJO]

I use lead-based solder, no problems. Sure, it won't be ROHS compliant anymore but whatever. The lead-free stuff is more prone to cracking anyway.

 

[yhelothar]

I have somewhat of a similar problem with my 24" MVA.
If I leave the monitor on for over 10mins, and shut it off, I have to wait 5-15 minutes(depending on how long the screen was previously on) before I can turn it back on or the screen would just flicker on for a split second and turn right back off.
So would changing the caps fix this?

 

[blanketyblank]

I have somewhat of a similar problem with my 24" MVA.
If I leave the monitor on for over 10mins, and shut it off, I have to wait 5-15 minutes(depending on how long the screen was previously on) before I can turn it back on or the screen would just flicker on for a split second and turn right back off.
So would changing the caps fix this?

I'd say it's possible since the symptoms sound about the same. Of course I'm not exactly sure my problem will be fixed till I actually do this. Why not try opening up the monitor and looking at the caps? I didn't see any obvious problems with mine, but you might spot a bulge or leak.

 

[SparkyJJO]

I have somewhat of a similar problem with my 24" MVA.
If I leave the monitor on for over 10mins, and shut it off, I have to wait 5-15 minutes(depending on how long the screen was previously on) before I can turn it back on or the screen would just flicker on for a split second and turn right back off.
So would changing the caps fix this?

Yeah sounds like a crappy cap problem on the power board. Really, about 75% of power issues on LCD monitors are cap related. So many manufacturers use cheap ones, even in some of their better panels.

So far, my VX2025wm is still working just fine after 4 years. And I haven't seen any reports of common power problems, so I think viewsonic actually had their heads screwed on right when they designed it and used good caps in it.

 

[yhelothar]

Thanks for the info.
I looked up a guide on changing LCD capacitors, is this a good one?
http://www.aplusperfect.com/articles/lcd_capacitor_repair
Also do you guys have any recommendations on where to buy caps and which ones to get? Darn Soyo for using cheap capacitors. I guess I can't complain much for getting a nice MVA screen for so cheap.
Do I just change all of the capacitors with the flat top?

 

[SparkyJJO]

Get Panasonic FM or FC caps from digikey.com - pay attention to dimensions. It isn't a bad thing to go physically larger, as long as they will fit. in LCDs though, you typically don't have too much wiggle room.

Replace ALL the caps on the power supply/inverter board, if they are a crap brand. Don't care whether they are flat on top or not, because 1) they still may be internally failing and 2) you don't want to go back in there to replace them later anyway. The only exception to this would be the big fat primary filter cap. Usually rated at something like 120uF 400V or something like that. Those rarely go bad.

The caps on the video board usually aren't suspect to go bad, but do look them over. I had a couple small ones going bad from poor power quality coming from the power supply that was failing in one LCD.

The rest of that site looks pretty decent.

 

[yhelothar]

Get Panasonic FM or FC caps from digikey.com - pay attention to dimensions. It isn't a bad thing to go physically larger, as long as they will fit. in LCDs though, you typically don't have too much wiggle room.

Replace ALL the caps on the power supply/inverter board, if they are a crap brand. Don't care whether they are flat on top or not, because 1) they still may be internally failing and 2) you don't want to go back in there to replace them later anyway. The only exception to this would be the big fat primary filter cap. Usually rated at something like 120uF 400V or something like that. Those rarely go bad.

The caps on the video board usually aren't suspect to go bad, but do look them over. I had a couple small ones going bad from poor power quality coming from the power supply that was failing in one LCD.

The rest of that site looks pretty decent.

Do I need to take any safety precautions when working with the power inverter caps? That sounds dangerous.
Thanks again for the info.

 

[SparkyJJO]

Those caps are going to be low voltage (25V or less) most operate at 12V DC input. If you want to be sure it is discharged (especially the big filter cap on the primary side) just leave it unplugged for a few hours before working on it.

 

[blanketyblank]

Get Panasonic FM or FC caps from digikey.com - pay attention to dimensions. It isn't a bad thing to go physically larger, as long as they will fit. in LCDs though, you typically don't have too much wiggle room.

Replace ALL the caps on the power supply/inverter board, if they are a crap brand. Don't care whether they are flat on top or not, because 1) they still may be internally failing and 2) you don't want to go back in there to replace them later anyway. The only exception to this would be the big fat primary filter cap. Usually rated at something like 120uF 400V or something like that. Those rarely go bad.

The caps on the video board usually aren't suspect to go bad, but do look them over. I had a couple small ones going bad from poor power quality coming from the power supply that was failing in one LCD.

The rest of that site looks pretty decent.

I forgot to measure the caps before ordering. If I replace a cap with something smaller will it just get hotter because there is less dissipation or is the only problem having to bend the wires to get it to fit into the larger hole? Hopefully they should be the right size though since I didn't see too much variation on the site anyways. Great site btw cheap shipping and fast turn around.

 

[SparkyJJO]

Generally, all else being equal, the smaller dimension caps will not have as long of a lifespan. However, I doubt that will be an issue. I've used smaller ones before and had to bend the legs a little bit to reach the holes. Typically, the 10mm and 12.5mm diameter caps use the same leg spacing. 8mm uses a slightly smaller spacing. But they can be bent to fit.

 

[blanketyblank]

Thanks for the help. It worked, but the repair was a lot harder than I thought. The main difficulty was getting the old capacitors out since even after melting off the old sodder they were still stuck in there. After yanking out what I could I had to use a hammer and a pin in addition to the soddering iron order to force the reamins out of the holes. Maybe my soddering iron isn't hot enough to get to the sodder that's in the holes. After that putting everything in was easy. Seems the 25 V 470 I bought was too long and had a shorter diameter so I had to bend the wires a bit and install it slanted. Should last longer though.