A Tale of Two Dead Viewsonic VA720s

[Operandi]

A co-worker of mine had two dead identical Viewsonic VA720 LCD monitors that she was going to toss out unless I wanted them. So rather than being tossed into the junk heap I reluctantly took them on.

Now despite being identical models and being purchased at the same time the two panels are actually completely different on the inside.

Sample one; this unit turns on and powers up with a "no signal" message for about 1 second, then the power indicator turns amber indicating standby but it physically stays on. I've opened the unit up and I believe I've found the culprit; on what seems to be the main board of the panel there is a group of Elite (known to be problematic) capacitors one of which is bulged and appears to leaked slightly, pics below.




Is it safe to assume that replacing the junk Elite capacitors will bring the panel back to life?

The second VA720 is completely different internally. As opposed to the first unit this one received it's power from an external power 12v power brick. The internal boards are also completely different populated with Teapo caps that seem to be in good condition. The power brick is missing so I can't say for sure that it was the problem but it seems to me that it's likely. Now I've picked up a replacement PSU from an eBay store that supposedly specializes in this area but they've sent me the wrong unit twice. The 2nd PSU is the correct voltage and has the proper amperage ratting but the connector is too big. I'm a bit sick of dealing with this eBay source, can I just swap cut the end connector off and swap it for one of the proper size?

[starfury1]

Re: A Tale of Two Dead Viewsonic VA720s

ok I dont work on these things anymore so haven't got a clue these days on whats what
but yeah that caps history replace it with a quality Low ESR to be sure.
(its interesting to note the colour used)

Provided nothing else has been damaged the chances are good it will work

I would advise ripping any el cheapo caps of 470uf and up out and replace them.

bear it mind not always but a lot of problems are either in the PSU area or inverter area with TFT LCD type screens.

As to the power brick...if its meets the voltage and current power requirement (or better) then yeah I see no problem, Just MAKE SURE you get the polarity right, it may have protection from reverse polarity but don't count on it.

pity you haven't got a decent variable psu to test it with before you put your cash on the line for the brick...anyway with the other check the caps and replace any in that condition (guessing there none since you didn't post anymore pics)
then replace that one if its the only one for a quick test.

If it works ok I would get rid of any suspect caps or crap as above.
(look in the FAQ's for recommended caps rubycon, nippon chem etc)

there are those around here that would me more familiar with them then me so you might want to hang abit to see what else gets posted on it...

HTH

Cheers

[gonzo0815]

Re: A Tale of Two Dead Viewsonic VA720s

Just replace the most visible damaged cap or replace those in the main voltage rail (the one who is regulated by the SMPS controller).
If it then turns on, just replace the other bad boys and enjoy.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Well I replaced the end on the power adapter for the 2nd display but the monitor is still dead. It dose get power; the LED turns on and then blinks green but the display never lights up. I'm assuming this one is a lost cause?

I'll be tackling the other Viewsonic next. In addition a friend of mine had a pretty nice 19" NEC die on him so I'll take a look that to see if anything can be done.

[Harvey]

Re: A Tale of Two Dead Viewsonic VA720s

Well I replaced the end on the power adapter for the 2nd display but the monitor is still dead. It dose get power; the LED turns on and then blinks green but the display never lights up. I'm assuming this one is a lost cause?

Could just be a back light fault. Is there anything showing on the display?

Try holding a torch close to it while it has a signal from a PC and switch it on - you should be just able to see the display if its working.

[kc8adu]

Re: A Tale of Two Dead Viewsonic VA720s

btw torch=flashlight on this side of the pond.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Could just be a back light fault. Is there anything showing on the display?

Try holding a torch close to it while it has a signal from a PC and switch it on - you should be just able to see the display if its working.

I had that thought too but the LED flashes green which would seem to indicate something isn't working properly. The other model with the failed cap goes right into standby with the typical amber color. Besides if it's the back light it's probably not worth fixing that that point.

btw torch=flashlight on this side of the pond.

Haha, I knew what he meant but thanks .

[tvtech]

Re: A Tale of Two Dead Viewsonic VA720s

Well I replaced the end on the power adapter for the 2nd display but the monitor is still dead. It dose get power; the LED turns on and then blinks green but the display never lights up. I'm assuming this one is a lost cause?

I'll be tackling the other Viewsonic next. In addition a friend of mine had a pretty nice 19" NEC die on him so I'll take a look that to see if anything can be done.

As for that 19 inch nec try resoldering the larger SMD resistors on the inverter board.I have had several that the backlight would work intermittently and resoldering the SMD resistors fixed it

[Krankshaft]

Re: A Tale of Two Dead Viewsonic VA720s

The blinking led is probably a fault with the display board. I had a Samsung 175V with the exact same problem when the cable wasn't plugged in it said No Signal when a cable was plugged in the led simply flashed on and off.

Indicating it was plugged into a source but it was acting as if it had no signal even though it did.

The display board signals the inverter to come on if one of two conditions are met:

1. The monitor is plugged into a VGA source (and is outputting a signal).

2. The monitor isn't plugged into a VGA source (Check Signal Cable).

A swap of the display board revealed that the old display board was shot. Rather then pay $80.00 for a new display board I just scrapped it.

Samsung doesn't even use Genesis LCD driver ICs they use some custom crap that I can't even get datasheets on.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Yeah, these Viewsonics were nothing special when they were brand new 4 years ago so I'm done messing with that one.

I have the NEC now and to my surprise when I plugged it in to see what happens it powered on just fine, both DVI and VGA. Only negative is a couple of scratches on the panel from sitting in the garage but they aren't too bad.

Now I just have to get some replacement caps for the other Viewsonic.

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

Same make, different model monitor. Same problem. [Elite caps]
I replaced all the Elite EB series (they were the brown ones).
Left everything above 16v alone (they were all black and a different series.)

The EB's are rated fairly high on ripple and low on ESR.
Pany FM (or better) will do the trick if you want to keep the ESR/Ripple near the original ratings.

On mine the PCB was drilled for both 3.5mm and 5mm lead space which made replacements easier. (I had to go up in diameter on a couple sizes to keep the ESR as low as the originals.)

Like Harvey said if it powers up but no display may mean just the backlight is out.
That's either the inverter or the lamps (or both). Those (and power to the inverter) are the only parts to the backlight circuit.
-
If that's the case the image is there but you just can't see it.
(Hence the 'torch' idea. hehehehe)

If you have the patience and time can you give us the quantity, size, and series of the original caps? (As in to build a cap-kit from.) - I've been keeping my eyes open for dead LCD's to play with.

VA is Viewsonic's value series so you're right, they aren't anything 'special', but they are still a better than a value brand LCD.

.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Same make, different model monitor. Same problem. [Elite caps]
I replaced all the Elite EB series (they were the brown ones).
Left everything above 16v alone (they were all black and a different series.)

The EB's are rated fairly high on ripple and low on ESR.
Pany FM (or better) will do the trick if you want to keep the ESR/Ripple near the original ratings.

On mine the PCB was drilled for both 3.5mm and 5mm lead space which made replacements easier. (I had to go up in diameter on a couple sizes to keep the ESR as low as the originals.)

Like Harvey said if it powers up but no display may mean just the backlight is out.
That's either the inverter or the lamps (or both). Those (and power to the inverter) are the only parts to the backlight circuit.
-
If that's the case the image is there but you just can't see it.
(Hence the 'torch' idea. hehehehe)

If you have the patience and time can you give us the quantity, size, and series of the original caps? (As in to build a cap-kit from.) - I've been keeping my eyes open for dead LCD's to play with.

VA is Viewsonic's value series so you're right, they aren't anything 'special', but they are still a better than a value brand LCD.

.

It receives power but the LED indicator flashes on and off so it's not operating in a normal power on state.

You can see the caps in the OP. The only visible bad one is the 10v brown cap. There are two smaller black ones I was going to replace also just to be safe, 16v 470 uf I believe (I don't think you can see the value in the pics). I'll post the exact values tomorrow.

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

I didn't have any 16v or below that were not brown EB series on mine.

The black one I think you are talking about does not have a vent which means it's not low ESR with a high water content. (Although that doesn't mean it didn't go bad. Just usually those aren't a problem.)

The flashing green light probably means the signal from the ID chip in the monitor isn't getting to the video card. - The computer doesn't know there is a monitor there so it isn't loading drivers and sending a video signal. That keeps the monitor in standby.

.

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

Modern monitors have a firmware that reports to the PC what it's settings are.
[Acceptable resolutions and frequencies.]
- a.k.a. - Plug-n-Pray.

If the PC isn't getting that signal it won't send a video signal out because it doesn't know what signal to send.

Your video card may support manual freq/resolution settings and you can possibly use that to bypass the requirement for that signal being present.
[Just make sure you use settings compatible with the monitor.]

.

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

And if you go to manual settings use settings that are the same for both your good and bad monitor. - That way you won't kill something with manual settings while you are switching monitors around.

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

Oops, sorry. The black one does have a vent.
(Didn't see it until I zoomed the picture out.)

The only similar one on my inverter was 35v and 100uF.
It was in the first stage of the power supply section (not actually in the inverter circuit) so I left it alone.

.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

Here are the values...

Brown Elite x1 1000uf 10v (the blown one)
Black Elite x3 470uf 25v
Black Elite x1 330uf 16v

Obviously the brown 1000uf cap has to go but should I also replace the 470 and 330 caps or are those small enough to not worry about?

[Krankshaft]

Re: A Tale of Two Dead Viewsonic VA720s

From my experience replace everything 100uf and over.

ALWAYS replace at MINIMUM ALL of the secondary capacitors and the PWM ICs supply capacitor.

I had an inverter full of those Elites on my HP L1955 (Benq) monitor.

The caps weren't the problem but I replaced them anyways so they don't become one later.

I personally replace all the caps on the inverters since there aren't really that many anyways and unlike other components caps are relatively cheap.

As for capacitors Panasonic FCs take the Sahara Desert temps in LCD inverters well you can find them at Digikey.

[PCBONEZ]

Re: A Tale of Two Dead Viewsonic VA720s

Here are the values...

Brown Elite x1 1000uf 10v (the blown one)
Black Elite x3 470uf 25v
Black Elite x1 330uf 16v

Obviously the brown 1000uf cap has to go but should I also replace the 470 and 330 caps or are those small enough to not worry about?

I would replace all of those you mentioned.
I would replace all of any model/series that has a failed cap on the board.
-
It's not that much more expensive to do them all since it's apart anyway and considering the hassle of taking it apart again to do them later it just makes sense to do them all now.

-
The ESR/Ripple ratings of the brown Elite 'EB' series FAR exceeds the ratings for Panasonic FC's however.
If you want to stay near the original ESR/Ripple ratings the board was (presumably) designed to use there then use Panasonic FM (not FC) in place of the Elite 'EB' caps.

FM is also available at Digikey.

I can't read the series on the black cap so I don't know the series or ESR ratings on those. [I personally have not seen a black Elite (meaning series other than EB) fail so I don't know if they are even a problem.]

Depending on where they are in the circuit 470 and 330 can matter on an Inverter board. Inverters are high frequency devices. I'm guessing by the uf/volt values of the ones you mentioned that they are in the actual inverter (vice the power) circuit. If true then they matter.

So: If the 330 and 470 are 'EB' then replace them with Panny FM (or better).
If they aren't EB's then your guess is as good as mine.

.

[Operandi]

Re: A Tale of Two Dead Viewsonic VA720s

What about Samxon caps? I was thinking of getting my caps straight from Badcaps.net.