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Old 06-14-2012, 10:22 AM   #61
Bilbo_UK
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Thank you guys so much! I thought my trusty VX1940W was heading for recycling this morning and I was going to have to stump up for a new monitor.

Classic symptoms of the "2 seconds to black" - buzzing and then power to standby. Started with the odd bzz last night but seemed otherwise ok, but then this morning it worked for 15 minutes and then no more. Switching off and counting to "5 elephants" before switching on again allowed it resurface for, err, 2 seconds, and then off again.

Inspired by you guys here (side-credit Google!) I opened it up and found the usual state of C1 and C302 with rounded tops. ( http://badcaps.net/forum/attachment....7&d=1294506657 ) Replacement caps (5 of 6) due to arrive tomorrow :-) I'll report back with results.



Oh one thing... how does the ribbon cable detach from the top of the display? (see pic) I didn't want to pull it the wrong way in case I ripped the ribbon out (been there, done that!) - I was able to extract it but it will be easier to put back together if it was apart (IYSWIM).


(hint for searchers: similar threads:
http://www.badcaps.net/forum/showthread.php?t=6989
http://www.badcaps.net/forum/showthread.php?t=17160 )
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Old 06-14-2012, 11:02 AM   #62
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

No actual experience of this monitor but it will either just be a push fit or
there will be a very thin (easily snapped) bar that runs the length of the connector and swivels at each end. They are usually a different color to the body of the thing so cant really tell on your picture. you have to lift both ends at once or it will snap.

This shows one but it has been glued down
http://www.mp3car.com/lcd-display/11...glued-pic.html
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Old 06-14-2012, 11:34 AM   #63
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

The white bar next to the blue making flips up to release the cable.
http://s807.photobucket.com/albums/y...t=DSC01163.jpg
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Old 06-14-2012, 12:30 PM   #64
Bilbo_UK
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Cool - easy when you know how! Thank you


p.s. for the black connectors does the ribbon just push in? (I don't need to disconnect this one but I'd like to learn how)

Last edited by Bilbo_UK; 06-14-2012 at 12:41 PM..
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Old 06-14-2012, 03:37 PM   #65
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

The black connector is the push-in type just make sure to push the ribbon cable back in straight in since the exposed conductor traces at the end do lift off the base substrate easily.
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Old 06-14-2012, 11:50 PM   #66
Bilbo_UK
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Thanks for that.


Ironically the monitor is still within warranty for another 3 weeks. (How do these things know? I'm sure they have a timer chip in them which is programmed to self-destruct 1 month after warranty expiry!) But then I would have to pay RTB postage and I can't find another similar resolution monitor so ViewSonic would probably have sent a lower res replacement which I don't want. 1680x1050 seems to be a "non-standard" size nowadays - the manufacturers seem to stop at 1440x900. I reckon it's because everyone's going blind from watching 60" TVs from only 3' away!

And besides where's the fun in just getting a new one?
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Old 06-15-2012, 12:02 AM   #67
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

A 'self destruct' just after warranty....Tut Tut(I'm English),,, you probably think that some of the very low quality Caps that are used in some monitors are 'built in obsolescense ' Tut Tut,BUT for the conspiracy theorists ??????
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Old 06-16-2012, 07:20 AM   #68
Bilbo_UK
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Thumbs up Re: 2 Viewsonic VX1940W buzzing and no signal

Thank you chaps, thank you so much! I now have a working monitor again.

I've never (successfully) done anything like this before, but you inspired me to have a go.

Cutting through the gunk around the caps was tricky - the gunk was very hard - just be careful with that knife!

I had a bit of trouble getting the old solder off - I had to put my iron on max temp before the wick would work.

And refitting the little 22uf cap (C205) was a little fiddly, due to the proximity of lots of other stuff on the soldering side. I had to have two goes at that one - I wasn't happy with the quality of my first attempt so I took it out again and redid it (with a fresh cap). Much better second time around

Put the monitor back together (and with no screws left over ) switched on and... it just did what it's supposed to do! No buzzing, no 2 secs to black - it just worked. Re-set it as my primary monitor and I'm using it as I type.



For anyone else in the UK these are the components I used (from RS Components) (thanks mariushm)

526-1660 (2 off) http://uk.rs-online.com/web/p/aluminium/5261660/
708-3661 http://uk.rs-online.com/web/p/aluminium/7083661/
725-8940 http://uk.rs-online.com/web/p/aluminium/7258940/
572-467 http://uk.rs-online.com/web/p/aluminium/572467/

Rogues gallery - see pic!
.
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Old 06-16-2012, 07:37 AM   #69
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Well done, good fix, nice to get some feedback - thanks
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Old 11-23-2012, 12:55 AM   #70
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

hello guys..I have the same monitor but the problem is my lcd panel....when I attached its connector to the mainboard the blue light indicator stopped after 3-5 seconds...lamps is ok...powerboard is ok...I got a new replacement for the powerboard...just the lcd panel is causing the powerblackout when it is attached to the main board.
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Old 04-01-2013, 10:09 AM   #71
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Well my repairs kept my trusty monitor in service for a further 8 months until it went bang. Big bang. Very loud and scary. I opened it up and discovered that part of the primary power circuitry had literally blown its top. It's hard to see from the photo but the ic marked in yellow in pic 3 has exploded - I found the bit blown off stuck on the black protective film. If I look closely I think some of the resistors are a bit dodgy as well - I can no longer read the writing on them and it looks like they've got hot and partially melted on the top? (R219, R222, R221 & R225).

This has obviously gone beyond my ability to repair it.

I had a hunt a round and found a couple of places which mentioned that the Delta DAC-19M020 is a drop-in replacement for my Darfon B092. Looking at the output specs they seemed similar enough:

B092:
DC output: 5V 2.5A
AC output: max 7.5mA 1000V

DAC-19M020:
DC output: 5V 2.5A
AC output: max 7.5mA 1300V

I tried to find out which is the newer design but couldn't find any info on this.

I found a chap in China selling them for 15 delivered so I took a punt. It arrived within 8 days and well packaged. I plugged it in and it fitted no problem and, fingers crossed, it's working well. I'm a happy boy again!


Pics 1-4 Darfon board
Other pics Delta board
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Old 11-30-2014, 08:02 AM   #72
mihu
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Based on this topic I successfully repaired a viewsonic vx1940w recently. It works fine after about 1 month after repair.
Here are some pictures.
Thank you for the info.
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Old 01-07-2015, 01:45 PM   #73
jose.veliz.32
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

I'm a beginner amateur electronics troubleshooter that had the two 220uf 35v caps bulged. I have plenty of monitors and only working on this to learn as I can easily replace the board.

After following this thread I replaced both caps with some off brand new caps of the same values and immediately after applying power, one of them blew (the single 220uf 35v).
I decided to replace all the caps (except main filter cap) with generic stock caps i had with as close values but higher as i could just to take measurements.

I have around 160V at the main filter cap, 5v off pins 1,2,3 on the secondary and 9.3v constant on pin 1 @ TEA1530AP.

If I'm not getting around 330v on the main filter cap and 5v at the secondary pins, does the below apply?

"3. A failure in the TEA1530AP. The capacitor never charges to the point the SMPS controller will start. The symptoms are no output voltage, no ticking sound, and a steady voltage at pin 1 below 10.3 volts."

Thanks.

I also posted a similar post on a different site about my lcd tv with powerboard failure. I replaced the board but still want to troubleshoot the problem if anyone is interested in helping. I don't know if I can post the link here or not so please let me know.
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Old 01-07-2015, 01:52 PM   #74
jose.veliz.32
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

I can also add that I tested the main filter cap out of circuit with a cheap chinese semi conductor tester (esr) and it showed .8 esr and ok uf.

Q: Does the board need to be turned on by one of the secondary pins in order to get correct main filter cap/TEA1530AP readings? I tested just the power board plugged in without any loads.
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Old 01-07-2015, 01:53 PM   #75
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Jose. Are you aware that caps have polarity?- perhaps the one that exploded was the wrong way round.
Please post good clear pictures of both sides of your boards - use manage attachments.
On a power supply you should be using good quality low esr caps.

EDIT you need it all connected up for it to fully start the power supply

Last edited by selldoor; 01-07-2015 at 01:55 PM..
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Old 01-07-2015, 03:29 PM   #76
jose.veliz.32
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Default Re: 2 Viewsonic VX1940W buzzing and no signal

Thanks for your reply selldoor.

It's exactly the same as the original post, didn't see point of adding more pics that were already submitted but I can certainly do that when on my home pc.

I am aware of the polarity in capacitors and to the best of my knowledge it was correct but I can see that as a possible answer since I didn't bother to look after it popped.

Since my purpose is to troubleshoot, right now my concern is not the quality of the capacitors. I have these on hand and once it has been fixed I can get better caps.

Can't I simply ground the on/off pin on the secondary to turn it on?
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