Lot of Viewsonic VA902 being recapped

[KyleSTL]

I have 9 Viewsonic 19" VA902 monitors that I am recapping. I first disassembled them and found bad caps in all of them. I put in a Digikey order for enough to fix them all. I was very meticulous in keeping the LCD screens of each one with the original display controller board. Two nights ago I removed all the bad capacitors from the PSU board, but left one in-tact for an example to reference while I put on the new caps. Today I got the order in and started to recap. After 3 montiors back together, not a single one works properly (1 the backlight is not coming on [likely a loose connection or something], but the other two are green and flickering). I can still see my desktop on it, but all the pixels have a green tint. What have I possibly done wrong. Before disassembly I confirmed all the monitors exhibited the two second power-off symptom of bad caps, and none of them had any kind of bad tint to them. Please advise.

Do power supplies need to stay with the original montior they came from? Is it bad I'm likely mixing and matching them?

[PlainBill]

Re: Lot of Viewsonic VA902 being recapped

I have 9 Viewsonic 19" VA902 monitors that I am recapping. I first disassembled them and found bad caps in all of them. I put in a Digikey order for enough to fix them all. I was very meticulous in keeping the LCD screens of each one with the original display controller board. Two nights ago I removed all the bad capacitors from the PSU board, but left one in-tact for an example to reference while I put on the new caps. Today I got the order in and started to recap. After 3 montiors back together, not a single one works properly (1 the backlight is not coming on [likely a loose connection or something], but the other two are green and flickering). I can still see my desktop on it, but all the pixels have a green tint. What have I possibly done wrong. Before disassembly I confirmed all the monitors exhibited the two second power-off symptom of bad caps, and none of them had any kind of bad tint to them. Please advise.

Do power supplies need to stay with the original montior they came from? Is it bad I'm likely mixing and matching them?

The power supplies are not individualized for each monitor, so some other problem is occurring. Your technique is good - keep one 'reference' board.

The fact that there are three failures indicates some sort of common problem, either soldering technique, handling, or the components you installed.

As a first step, check the location and orientation of the caps you installed in one board to those in the 'reference' board.

Next, list the value, voltage, brand, and series of the original caps, and the same information for the replacements, and post it here.

At this point I am trying to figure out what could have happened to cause a bad tint.

PlainBill

[alexanna]

Re: Lot of Viewsonic VA902 being recapped

Looking at the other va902 thread, the VGA cable stays with the monitor.
If yours is the same way, try flexing and bending the VGA cable see if you can get the colors to change.

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

PlainBill,

The old caps were all Su'Scon brand (I'll have to check the series later) with the following ratings:
(1) 25V 1000uF
(3) 25V 220uF
(2) 10V 1000uF

I replaced all of them with Nichicon VZ series caps of the same capacity. All polarity is correct. I will take pictures sometime tonight, or early next week and upload them (front, back, and ribbon cable to the LCD). My power supply board looks considerably different than the one depicted in the old VA902 thread. Also, I realized this morning that my reference board is gone, so I think late last night when I did the fourth one, I accidently installed it into one of the monitors with the old, busted caps still on.

Alexanna,

The ribbon cable on the monitors I have is a removable locking cable, that was my first thought, too, is there is some kind of bad connection. I will try to play around with it to see if i can get it to work.

[jsog]

Re: Lot of Viewsonic VA902 being recapped

Nichicon VZ is a general-purpose series, not low ESR.

[alexanna]

Re: Lot of Viewsonic VA902 being recapped

Not the ribbon,The VGA cable that hooks to the video card on the PC

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

Ah, all my versions had removable external cables for the VGA to the computer. I just saw you're in St Louis. I am as well.

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

Jsog,

What would be a good low ESR cap that goes up to 25V? I looked at the preferred caps thread (after I had already ordered them, of course - measure once, cut twice) and a lot of them only went up to 16V.

EDIT: Nevermind, clicked through them and figured out which were up to 25V.

Is there any way to tell if the non-low-ESR caps are my problem?

[alexanna]

Re: Lot of Viewsonic VA902 being recapped

Order and replace the caps with low ESR.
You have 4 monitors one has no back light and 3 with strange colors.
Try a different VGA cable, or at least Bend and flex the old one see if the color changes.


GO CARD'S

[PlainBill]

Re: Lot of Viewsonic VA902 being recapped

Jsog,

What would be a good low ESR cap that goes up to 25V? I looked at the preferred caps thread (after I had already ordered them, of course - measure once, cut twice) and a lot of them only went up to 16V.

EDIT: Nevermind, clicked through them and figured out which were up to 25V.

Is there any way to tell if the non-low-ESR caps are my problem?

Take the unmodified power supply / inverter, hook it up to a signal board, LCD panel, and VGA cable that exhibited the greenish tint. If it has a greenish tint for the two seconds, the problem is NOT the power supply.

The flickering DOES indicate a problem with the inverter or inverter supply.

PlainBill

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

Thanks for the help guys. I have ordered new caps for all the monitors (United Chemi-Con KZE series). Should be in next week, I'll repost when I get them in and installed. Should have been more diligent before making the first order.

alexanna, the Cardinals are my second favorite team (behind the Reds, since I'm from south-west Ohio). I'm going to the game tonight against the Reds with my company's corporate tickets. Should be quite enjoyable.

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

Just to follow up, the United Chemi Con KZE caps have worked wonders since September. I have fixed (13) VA902B monitors, and six other makes/models since then. I have been credited with saving my company thousands of dollars. Thank you PlainBill, jsog and alexanna for your help.

[shovenose]

Re: Lot of Viewsonic VA902 being recapped

Success stories are always nice!
better than tossing tons of monitors in the landfill and spending thousands on new ones

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

Update on my monitor project. I have successfully repaired 31 monitors for my company to date (including 23 of this exact model). However, there are 3 monitors [of this model] I have not been able to make fully functional (despite recapping with KZE on all 6 filter caps), and by constructing many permutations of known good parts, I have determined that all 3 have issues solely with the power board. Monitors A & B have the same problem, and Monitor C has a different problem - I'll explain them below:

Monitors A and B -

LCD display works fine, but backlights do not function at all (confirmed using separate power supply for backlights)

Monitor C -

Clicks on and off constantly at ~2 sec interval. When hooked up to a good LCD panel it flashes the displayed image for a fraction of a second, then goes to a vertical line pattern and repeats until the monitor is turned off again. See youtube link below:

http://youtu.be/kYW9Qk2qYnQ

Any help is greatly appreciated.

[Rtech]

Re: Lot of Viewsonic VA902 being recapped

U 501 and 502 are AP605..these regularly fail on other Power supplies,so would check them.Also compare resistance readings from good boards on the Inverter transformer secondaries,.

[KyleSTL]

Re: Lot of Viewsonic VA902 being recapped

Thanks, Rtech, for your assistance. Couple questions on it though:

1) How do I go about testing the ICs (it has been quite some time since my circuits class in college, and I'm a ChemE, so they went pretty light on the electronics courses)?
2) Are the inverter transformers the two high voltage ones near the backlight plugs?

Thanks in advance for your help.

EDIT: Nevermind, I think I found the information I needed by searching the forum. Thanks again.