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-   -   Monitor Turns off after a few seconds with new caps (http://www.badcaps.net/forum/showthread.php?t=8176)

TimmieT 11-04-2009 11:14 PM

Monitor Turns off after a few seconds with new caps
 
I have two monitors at work, one is a 22" Viewsonic and one is a 22" Gateway. The Viewsonic had around 4 bad caps so I replaced all of them with the equivalent Panisonic FM caps. The Gateway didn't seem to have any bad caps, but I replaced mostly all of those as well. I tested all the CCFL's with an inverter from CCFL computer case lights and they all seem ok. I'm not sure where to go from here. Both monitors light up for a second then turn off. Thanks for the help

Krankshaft 11-04-2009 11:56 PM

Re: Monitor Turns off after a few seconds with new caps
 
Bad inverter transformer driver transistors take some pics of the boards and I'll circle them for you.

TimmieT 11-05-2009 10:11 AM

Re: Monitor Turns off after a few seconds with new caps
 
2 Attachment(s)
Thanks
Let me know if you need better pics

TimmieT 11-07-2009 05:33 PM

Re: Monitor Turns off after a few seconds with new caps
 
3 Attachment(s)
I think these are what I need? The problem is I can't find them on Mouser, or Digikey. Are these what I need, and if so any idea how to replace them?

mockingbird 11-07-2009 08:06 PM

Re: Monitor Turns off after a few seconds with new caps
 
Quote:

Originally Posted by TimmieT
I think these are what I need? The problem is I can't find them on Mouser, or Digikey. Are these what I need, and if so any idea how to replace them?

Correct me if I'm wrong but I believe those are called MOFSETs. Check Digikey.

TimmieT 11-07-2009 11:03 PM

Re: Monitor Turns off after a few seconds with new caps
 
Thanks for the help.
I think your right, MOFSETs.
I can't find any info on the part numbers, so I don't know what to order.
Can you just buy a higher rated MOFSET, or do I need to know the voltage and other specs. If so, does anyone have a way to find some info on these parts?? Thanks for all the help.

PCBONEZ 11-07-2009 11:28 PM

Re: Monitor Turns off after a few seconds with new caps
 
The parts you are calling MOSFETs probably aren't the xfmr driver transistors.
The xfmr driver transistors are the usually the small old style 3-legged jobs.
They basically cut power to transformer primary on-off to make it higher voltage AC.
The drivers are the "switchers" in a SMPS.
What you are looking at in pics are on the secondary side of xfmr.
They take the higher voltage AC and turn it back to DC again.
.

Toasty 11-08-2009 12:45 AM

Re: Monitor Turns off after a few seconds with new caps
 
Both of those boards probably have the drivers on the solder side as flat packs or SMD's, since I don't see them on top (but the pics are very small). I don't think they are bad, as it does work for a second or so.

I'd be suspicious of the HV transformers, output caps (little round blue ones), or the tubes. I believe the current monitor circuit is sensing an overload and shutting them off. Also check and resolder the HV transformer connections. It's a common failure point on various makes & models of inverters.

>>I tested all the CCFL's with an inverter from CCFL computer case lights and they all seem ok.<<
Now try it the other way around. Try running the case lights with the inverter. Do Not run it for more than a few seconds for each tube.
** DO NOT RUN THE INVERTER WITHOUT THE TUBES CONNECTED **

Can you post some larger top side pics and equally sized shots of the solder size?

Toast

TimmieT 11-08-2009 02:11 AM

Re: Monitor Turns off after a few seconds with new caps
 
2 Attachment(s)
** DO NOT RUN THE INVERTER WITHOUT THE TUBES CONNECTED **
Already did that. oops
Hope I didn't make it more dead.
I don't have the rest of the monitor here, it's still at work so I'll have to try the ccfl's from the case lights on monday. Here are some better pics.
Thanks again for all the help from everyone.

PlainBill 11-08-2009 05:05 AM

Re: Monitor Turns off after a few seconds with new caps
 
1 Attachment(s)
Quote:

Originally Posted by TimmieT
** DO NOT RUN THE INVERTER WITHOUT THE TUBES CONNECTED **
Already did that. oops
Hope I didn't make it more dead.
I don't have the rest of the monitor here, it's still at work so I'll have to try the ccfl's from the case lights on monday. Here are some better pics.
Thanks again for all the help from everyone.

I've marked up the picture of the bottom of the Gateway board. The IC in the dark red circle is the inverter controller. The two ICs (actually FETs) in the bright red circles are the drivers for the inverter transformers.

I'd agree with PCBONEZ. The drivers are probably fine. Certainly if each output will light up a CCFL for a few seconds the drivers are good. (Note that it is difficult to determine if all four monitor CCFLs are lighting in the few seconds they are on. You have to see individual CCFLs.) The components circled in blue make up the monitor circuitry for each pair of CCFLs. The outputs of these circuits lead back to the inverter controller.

PlainBill

Krankshaft 11-08-2009 05:39 AM

Re: Monitor Turns off after a few seconds with new caps
 
1 Attachment(s)
Look at those cracked joints on the inverter transformers and on the CCFL output jacks! The first pin on both of those CCFL transformers looks completely cracked all around!

Resolder everything circled in red and go over the board with a magnifier and check for more. If I found that many from the pic I'm sure there's more.

This is Standard Operating Procedure for me to go over any board after I replace the defective components so I don't usually mention to check for cold joints.

Sheesh who runs QC on these wave soldered boards?

PlainBill 11-08-2009 06:04 AM

Re: Monitor Turns off after a few seconds with new caps
 
Quote:

Originally Posted by Krankshaft
Look at those cracked joints on the inverter transformers and on the CCFL output jacks! The first pin on both of those CCFL transformers looks completely cracked all around!

Resolder everything circled in red and go over the board with a magnifier and check for more. If I found that many from the pic I'm sure there's more.

This is Standard Operating Procedure for me to go over any board after I replace the defective components so I don't usually mention to check for cold joints.

Sheesh who runs QC on these wave soldered boards?

QC? Krankshaft, these boards come from China!! The country where someone put melamine in baby formula to increase profits!!

PlainBill

Krankshaft 11-08-2009 08:12 AM

Re: Monitor Turns off after a few seconds with new caps
 
I'm willing to bet this is due to the lead free solder craze started by the EU many manufacturers still can't get it right.

Or they are using their old leaded solder equipment which isn't designed for lead free creating these joints.

Toasty 11-08-2009 11:24 AM

Re: Monitor Turns off after a few seconds with new caps
 
>>I'd agree with PCBONEZ. The drivers are probably fine. <<

:confused:

PCBONEZ 11-08-2009 12:50 PM

Re: Monitor Turns off after a few seconds with new caps
 
Passing credit memo to Toasty.

EGuevarae 11-08-2009 04:45 PM

Re: Monitor Turns off after a few seconds with new caps
 
Just for informational purposes, exactly what LCD brand/model is being discussed here (and pictures posted) ? :redface:

TimmieT 11-09-2009 11:56 AM

Re: Monitor Turns off after a few seconds with new caps
 
The models are a Gateway HD2200 and a Viewsonic VX2255WMB

TimmieT 11-09-2009 11:48 PM

Re: Monitor Turns off after a few seconds with new caps
 
Today I resoldered all the spots on the board other than the two small chips.
Still seemed the same. I then tried to plug the tubes from the Viewsonic in and that stayed on. It seems like 3 of the 4 tubes are bad. Could a bad solder point make 3 die at the same time?(kinda dead they still light for a few seconds) I guess I need some new ccfl's. How hard are they to change? I've done a few on laptop lcd's but lately I've just replaced the whole lcd. I never get the ccf'l's to fit right and the screens always distort.

I also just read this post about re-doing the solder on the end of the ccfl's
http://www.badcaps.net/forum/showthread.php?t=8184

toi909 12-22-2009 04:59 PM

Re: Monitor Turns off after a few seconds with new caps
 
did you ever fixed you gateway hd2200? i dont know anything about any of this but am interested in learning. this is my first time. i have same problem with this hd2200 i got for free. my power board looks a lot nicer then yours(no offense). tested all the caps to the best of my knowledge with a ddm. for some reason i focused more on the other circuit board, the one for the video and what not, since theres power and all, it just shuts off to stand by mode. notice that the biggest cap,(820uf, 25v) read upsidedown. changed it to the best of my knowledge and its still the same.

sorry for such a long type. im totally new to all this. i dont even know how to solder let alone use my cheap radio shack ddm.

toi909 12-26-2009 12:12 PM

Re: Monitor Turns off after a few seconds with new caps
 
still have this gateway hd2200, i removed the invertor hoping i could just buy it at radio shack. how naive i am. can anyone show me where i can get one ? the reason why i removed it was because it smelt burnt. really hope i can get this monitor going. thanks in advance.

EGuevarae 12-26-2009 06:52 PM

Re: Monitor Turns off after a few seconds with new caps
 
Quote:

Originally Posted by toi909
still have this gateway hd2200, i removed the invertor hoping i could just buy it at radio shack. how naive i am. can anyone show me where i can get one ? the reason why i removed it was because it smelt burnt. really hope i can get this monitor going. thanks in advance.

Post pics and cap info. No one will be able to help you a lot without information, because even as you posted twice, you've said almost nothing of the unit (no offense)
:feedback:

Michael Long 02-24-2010 10:16 PM

Re: Monitor Turns off after a few seconds with new caps
 
I replaced all Caps on a Viewsonic vx2255wmb inverter board DAC-19M011, no joy.
no lamp activity. Monitor works with borrowed power supply inverter board.
What is the next recommendation? Could someone point me to the transistors and
digi-key p/n to procure.

EGuevarae 02-24-2010 10:59 PM

Re: Monitor Turns off after a few seconds with new caps
 
Quote:

Originally Posted by Michael Long
What is the next recommendation?

Pics. V output readings from PSU :beer:


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