ViewSonic N2750W - 0 secs to black

[zedron]

Someone was going to throw out a ViewSonic N2750W but I said Ill take it and give it a shot at repair. We could always use another TV somewhere in the house right? My last attempt at Tv repair was very successful so I said why not. I have nothing really to lose besides maybe a few bucks in replacement caps, etc.

TV turns on and I can see the image in the back with a flashlight. I didn't hook it up to an input source but instead hit the menu button to get the OSD to appear and it does with a flashlight of course. So, I said OK, cant be to hard of a problem. Just got to get those back lights to turn on.

So far I tested the inverter board's transformers with the below results:
Trans#---Pins 1-8-----Pins 4-5
1-----------0.969--------0.966
2-----------0.959--------0.961
3-----------0.982--------0.981
4-----------0.986--------0.986
5-----------0.975--------0.972
6-----------0.967--------0.973
7-----------0.959--------0.961

Nothing is screaming out "IM BAD" here in relation to the transformers. I don't have a spare CCFL to test or a CCFL tester. The way this TV/Panel is setup makes it extremely hard to test as the inverter board is covered by the panel that the main board and PSU are on.
Any more help on what needs to be tested let me know. Appreciate the help. Pictures are below.

Pics#1,2 = Inverter Board with transformers numbered in red and caps circled in yellow. Didnt test caps as I think they are in parrellel adn I have not removed.
Pics#3,4 = Power Unit
Pics#5,6 = Main Board
Pic#7 = CCFLs

[zedron]

Re: ViewSonic N2750W - 0 secs to black

After looking over the boards some more thinking that it cant be this hard I noticed three caps on the main board looking a little bloated.

(2) Elite 1500uF 10V 105C
(1) Elite 1000uF 16V 105C
Survey says?

[R_J]

Re: ViewSonic N2750W - 0 secs to black

You did look at these pictures before uploading right? There should be some fuses on the inverter board, some are easy to spot and there is usually one that is very small and marked with a letter (fuse rating) that supplies the drive ic circuit.

Yes those caps are bad.

[budm]

Re: ViewSonic N2750W - 0 secs to black

I would replace those bad caps first, then verify that you do have 24VDC and BL_ON signal feeding the inverter board.

[zedron]

Re: ViewSonic N2750W - 0 secs to black

Pulled the caps out and tested.
The 1500 uF caps tested around 450-600uF
The 1000 uF cap tested around 200uF

I looked on the inverter board for F fuses and the only ones I found are F1-4 but they are empty.
Im gonna buy some replacement caps and see how she does.
Ill post back my results.

[zedron]

Re: ViewSonic N2750W - 0 secs to black

Unfortunately the cap replacement did not solve the issue. I checked the output from the PSU to the inverter board and it read 23.06V. I'm going to guess it a CCFL or something with inverter board. Anyone have any ideas to check? I don't have any CFLs lying around either or a CCFL tester. I was thinking about buying one of those CCFL tester on eBay for $6 to check and to keep in my tool box for other projects.

[budm]

Re: ViewSonic N2750W - 0 secs to black

"I looked on the inverter board for F fuses and the only ones I found are F1-4 but they are empty" They are not empty, there two footprints for two sizes of the fuses, next to the empty pads are white fuses, as you can see some of them has '3' printed on top to indicate 3A fuse which is also printed on the board.
http://www.shopjimmy.com/media/catal...40.027-top.jpg

http://www.shopjimmy.com/media/catal...j27d000703.jpg

[Agent24]

Re: ViewSonic N2750W - 0 secs to black

It's probably not a lamp fault since faulty lamps usually seem to at least try to light up, and then get shut down.

Check fuses like the others have said, if any are blown, I would say start with checking for shorted drive transistors in the inverter

[zedron]

Re: ViewSonic N2750W - 0 secs to black

"I looked on the inverter board for F fuses and the only ones I found are F1-4 but they are empty" They are not empty, there two footprints for two sizes of the fuses, next to the empty pads are white fuses, as you can see some of them has '3' printed on top to indicate 3A fuse which is also printed on the board.
http://www.shopjimmy.com/media/catal...40.027-top.jpg

http://www.shopjimmy.com/media/catal...j27d000703.jpg

Ahh I see what you mean. Whats the best way to check fuses, continuity? Forgive me if my questions are rather simple. Im in no way a electronics person but rather a network/voice engineer, lol.

It's probably not a lamp fault since faulty lamps usually seem to at least try to light up, and then get shut down.

Check fuses like the others have said, if any are blown, I would say start with checking for shorted drive transistors in the inverter

Thanks for the reply. Checking fuses.

[selldoor]

Re: ViewSonic N2750W - 0 secs to black

Fuses - No power to board you are testing - set meter on ohms 200
one probe to each side of fuse - should be same as touching the probes together.

[zedron]

Re: ViewSonic N2750W - 0 secs to black

Fuses - No power to board you are testing - set meter on ohms 200
one probe to each side of fuse - should be same as touching the probes together.

Got it, thanks.
Im going to go ahead and say that 3/4 fuses are shot. Im going to replace all 4 though since I am already in there. What kind of fuse would that be? There are no markings on it except the amperage rating.

[tom66]

Re: ViewSonic N2750W - 0 secs to black

If you found 3 fuses blown there's probably a fault on the board somewhere.

[zedron]

Re: ViewSonic N2750W - 0 secs to black

If you found 3 fuses blown there's probably a fault on the board somewhere.

Any suggestions for locating that or easier to get a new board?

[selldoor]

Re: ViewSonic N2750W - 0 secs to black

Are you absolutely sure the fuses are open. You did not actually give the result of the test.

It would possibly have a "1" on the left of the meter or "OL" or whatever your meter shows when the probes are apart. (obviously with the meter on)

First easy check would be the caps - just to see if they are shorted
Perhaps post pictures of the inverter in 3 sections close up for us to inspect better.
Nothing on the back?

[zedron]

Re: ViewSonic N2750W - 0 secs to black

Meter reads 0 when leads are apart
Meter reads .1 Ohms with leads together
Meter reads .1 Ohms testing "good" fuse
Meter reads 0 or bounces around and eventually ends back at 0 on "bad" fuses

Nothing on back.
Ill get some updated pics later this evening.
shopjimmy has a board for $20... :-/

[selldoor]

Re: ViewSonic N2750W - 0 secs to black

Board may be the way to go BUT make sure you get the exact same model /series and even when you think it is ok ring them up and make sure - we have had a few people buying the wrong boards lately . The important number is often the one on the barcode label
- not necessarily the one silkscreened on the board.

[tom66]

Re: ViewSonic N2750W - 0 secs to black

"0" with leads apart -- are you sure?

[zedron]

Re: ViewSonic N2750W - 0 secs to black

"0" with leads apart -- are you sure?

Yep positive.

0
Once I touch them together it goes to .1 Ohms

I sent an email to jimmy regarding the part number to verify. While I have been here on the site I have been lurking around and noticed that too with regards to incorrect item purchases. That's what prompted me to email them for verification.

[selldoor]

Re: ViewSonic N2750W - 0 secs to black

We dont disbelieve you but I dont think we have ever seen that before.
What is the make model of your meter? Picture of it?

[tom66]

Re: ViewSonic N2750W - 0 secs to black

I think your meter might be faulty...