Viewsonic 22" 2-sec to black - board or CCFL

[stormy1777]

This monitor I think is from 2008, it was having a hard time turning on so (power came on, but CCFL would light only after ~5-15minutes), 3 months ago, opened, replaced ONE bad CAP, and problem went away, it worked almost non-stop since then, but today, out of the blue, just turned OFF.

Turning on, and it fades to black within 2 seconds (power light still BLUE), not enough time to hit any key or attempt to reduce brightness. (I have not yet checked if image is visible with flashlight, will re-assemble it soon).

I've now replaced ALL caps, they were 7-10% off from marked rating (except the 120uF/450v - large blue), board is E131175 - anyone has schematics, or how much output goes on the CCFL driver plugs? I know it should be 600V+, but not seeing that:

1) Trying to figure out how to determine if it's the board not putting enough power, OR, the CCFL. Measured on the output connectors that go to the CCFL, and on board each (top in the image), shows ~4VAC, is this OK? I guess it will go much higher once the CCFL is connected properly?

The CCFL assemblies look nice, see images... Hopefully tomorrow i get more time, and disassemble further to see the CCFL themselves.

2) Also, tried to drive just ONE set of CCFL, i.e. blue+red cables (bottom of display), same fade to black occurred, and also same thing when the other pair was tested (top of display), each test was individually (thinking less power would make it work), obviously, both tested together produces the fade to black. Is it safe/valid to test just one pair of CCFL?

Any tips welcome.

[budm]

Re: Viewsonic 22" 2-sec to black - board or CCFL

I do not see the lamps, only the back side the lamps, the ends of the lamps are not blackened?
The protection circuit will kick in if it does not see all 4 lamps connected, it also detects if one or more lamps draw too much current. It will take only one bad lamp or one not connected lamp to shutdown the circuit.

[stormy1777]

Re: Viewsonic 22" 2-sec to black - board or CCFL

ok, I'll keep disassembling this to get to the lamps.. do u know if it is possible to test the OUTPUT on the board, with it plugged in, with a multimeter that is rated 750VCA? i only got 4VCA, that is strange...

[budm]

Re: Viewsonic 22" 2-sec to black - board or CCFL

Never try to test the HIGH VOLTAGE/HIGH FREQUENCY AC output feeding the lamps, the firing Voltage to get the lamp to start conducting can be as high as 1500VAC or more, you will destroy your meter.
I test the board using know good lamps or make test lamps from old CFL: https://www.badcaps.net/forum/showthread.php?t=19987
Blue Ballast cap c506 looks cooked with light tan color, the resistor next to it also got hot.
You will also need to test the resistance of the high Voltage windings of those two inverter transformer.

Bad lamps/wiring:
http://s807.photobucket.com/user/bud...?sort=3&page=1
You may have to tug on the wires at the end of the lamps to see if it will just come off.

[stormy1777]

Re: Viewsonic 22" 2-sec to black - board or CCFL

Thanks for that info!!!!! I naively assumed that since C523 & C506 both appear in symmetrical places, and both are "green", that is normal but now realize both should actually be BLUE..

How do i get their RATINGS, I don't see any markings it was all faded. tried searching for circuit plan online but have not found anything yet.

the blue caps NEXT to the green ones read: N3 3KV SEC (so 3nF, 3000V)

this looks similar to this thread:

http://mobile.badcaps.net/forum/showthread.php?t=23650

where you had helped someone else who says these had: 10p3kv markings.

their model is: VX2255 mine is VA2226W.

So, I'm not sure how to conclusively find the ratings, for now, I assume it is the 10p3kv, just like the other post, b/c they do look a bit smaller than the blue ones..


On spare boards I found many 12J 3KV which I assume to be 12pF 3000V

Is this "close enough", also, I assume polarity does not matter here...

meanwhile, searching for for more exact fit 10p3kv... hopefully can put back all the monitor/CCFL assembly, I think these are not the issue, the bad caps are definitely the issue

Regarding the Resistors next to these blue caps, both at R506 & R525 read 1.47MOhm in-circuit. so I think they are OK? or.. both bad

Thanks!
Stormy.

[stormy1777]

Re: Viewsonic 22" 2-sec to black - board or CCFL

UPDATE:

Put the 12J3KV (12pF), but same behavior of fading to black appears even faster now Digging more, found another board with 10J3KV, (10pF), and replaced these, but still same fading to black, also a bit faster than originally.

Took apart the CCFL assembly, and it seems they are bad, see 4 photos showing the edges, black and rusty in places....

This is 22", so guess I need: 483mm *2.4mm CCFL.. and replace all 4...

[stormy1777]

Re: Viewsonic 22" 2-sec to black - board or CCFL

Searching for CCFL, learned that it might be better/easier to convert it to LED..

Found many kits and most of the LED kits call for 9V or 12V, but as far as I can see, my power-board (main) has 5V, didn't see 12. Also the controller-board (smaller, photo attached), has the same 5V.. Questions:

1) Can I get 9v or 12v from the main board somehow? or should i search move to find an LED that is driven by 5V board, will that be bright enough?

2) Once this is working can someone tell which capacitors can be removed from the main board b/c the AC invertor won't be used at that point. So they don't heat up, or waste power?

Thanks.

Stormy.

[stormy1777]

Re: Viewsonic 22" 2-sec to black - board or CCFL

Quick update:

1) got new CCFL bulbs, replaced all 4, tested outside each bulb separately, all holds light for 1 minute, no issues.. when connected to board, same issue, turns on but ~2 seconds to black all lamps.

2) Pulled R506 next to C506, and measured 1.475MOhm, based on: https://www.allaboutcircuits.com/too...de-calculator/, BROWN, GREEN, GREEN, GOLD, it is 1.5M, so within margin of error.

3) budm mentioned to "resistance of the high Voltage windings of those two inverter transformer", but I have no clue how to go about that.

4) I guess it's a guessing game, to replace one part after the other? no way to somehow measure stuff to narrow down the area? I'll replace these blue caps again, b/c bought new ones, the ones i've put are from pulled board...

Any tips welcomed.

[stormy1777]

Re: Viewsonic 22" 2-sec to black - board or CCFL

quick update, i think the "N3 3KV SEC" is really 0.3nF (or 300pF), and not 3nF like I initially wrote above. Can only find 330pF, I'm assuming this is safe to replace.

any where to download/find the circuit plan for this board? too bad that they markings are not more "user friendly" or "universal" to conclusively figure things out