Samsung Syncmaster 932B

[retiredcaps]

Re: Samsung Syncmaster 932B

The caps i used arent low esr...and they are jamicon brand...maybe not good brand? The original caps from the inverter board wasnt low esr either....

SMPS applications require low ESR caps. Manufacturers make all sorts of different caps: general purpose, low ESR, etc.

I don't know if Jamicon makes low ESR caps or not.

If the caps are on the inverter are the originals, replace them with somethinig like Panasonic FR, FM, or FC (in that order) caps.

red and blue point value is blue 1,03 kOhm and red 1,06 kOhm

What is 1,03 kohm? Is that 1030 or 1003 ohms?

[Djadjo]

Re: Samsung Syncmaster 932B

The caps i used arent low esr...and they are jamicon brand...maybe not good brand? The original caps from the inverter board wasnt low esr either....

Ok ill easy replace caps to low esr...do you think that it will correct fault?
yes to mention i have resolder all posible solder points pins etc...


Ok i know that multimeter test is not good method to try caps...i can try to measure caps on lcr meter...but if a put new esr than its pointless

red and blue point value is blue 1,03 kOhm and red 1,06 kOhm


Sorry for the photo service...wont happen again...you can freely delete pictures


Tnx

Djadjo

[retiredcaps]

Re: Samsung Syncmaster 932B

So i have firstly changed all caps,all new and all are the higher value in voltage..

What brand and series did you use for replacements? It matters in a SMPS application if you used general purpose caps or low ESR caps.

the ones that was default on the inverter board,all were good...multimeter test

A multimeter will NOT test for ESR (ohms). You can meausure uF, but not ESR with a multimeter.

I have measured two blue point and red point on the inverter transformator..and both of the point were 1K ohm....so i presume its good

What is the exact reading? It should be 3% of each other.

PS. Please use the manage attachments function here to upload your pictures and please do not post inline. I will not look at pictures that are hosted offsite due to unwanted popups.

[Djadjo]

Re: Samsung Syncmaster 932B

Ok i have the same problem on my 932B panel...the display shows picture and than after one second backlight shuts down...
So i have firstly changed all caps,all new and all are the higher value in voltage..
the ones that was default on the inverter board,all were good...multimeter test
but the problem remains...

I have measured two blue point and red point on the inverter transformator..and both of the point were 1K ohm....so i presume its good
the problem remains...

I have lend from my friend the same monitor and try to figure out are on my panel ccfl tubes gone..but no..i mean i connect his inverter board and the panel works no problem...when i changed video motherboard it works too....
so the only problem lays on my inverter board....

I have come to conclusion that maybe the faulty sense circutry is cause to shut down backlight...

I only think that or SEM2005 or STU309D are faulty....

the ( U201) SEM2005 i cant found...Is there a substitute controler?
the ( U202 ) STU309D i orderd so i wait and give it a try with replacing

is there some other idea what to try

PS: i didnt say but all other components on the board are all measured with multimeter and didnt finde any burnt or too different reading of value...i have compare values with friends working inverter board...

Can i circumvent some pins on sem2005 error line to make it work on purpouse...so the sens will be shortened but it will leave backlight turned on






Thanx

Djadjo

[hartpunch]

Re: Samsung Syncmaster 932B

The exact symptom was the monitor was in use pretty much every day for over 2 years. Then two nights ago, it went blank. No warning, no intermittent, just dark. Turning off the power and waiting, it comes on for about 5-8 seconds then back light goes dark. It does stay on a little longer, maybe 10 seconds when it's cold (off for more than an hour) and that goes down to 5 sec as it gets warmer, so sounds like a component problem or lamp

[retiredcaps]

Re: Samsung Syncmaster 932B

Also, check the wiring carefully for shorts.

Like jetadm123 says there have been cases here where the problem was just the ccfl wiring gone bad. See below for examples ...

http://s807.photobucket.com/albums/y...klight%20lamp/

[jetadm123]

Re: Samsung Syncmaster 932B

Being a Lab Tech at heart, I couldn't give up on the troubleshooting. Reading other posts about the "flash light test" I did it and I have a picture, but the back light driver has gone South, I am thinking this because if a single BL went out, I would assume I would have a dim picture, ALL the back lights, I assume would mean the problem is in power supply itself, which is what all the posts point to. Thanks to all for the help, most educational.

You have 4 CCFL tubes. It only takes one bad tube to activate the CCFL controller protection circuit, which shuts down the power to the backlight assembly and kills power to ALL tubes, not just the bad one. The question is: do you get a brief flash of light when you try powering on the screen? If yes, you could try substituting a known good CCFL tube one at a time to see if you can get the backlights to come and stay on. Also, check the wiring carefully for shorts.

[hartpunch]

Re: Samsung Syncmaster 932B

Being a Lab Tech at heart, I couldn't give up on the troubleshooting. Reading other posts about the "flash light test" I did it and I have a picture, but the back light driver has gone South, I am thinking this because if a single BL went out, I would assume I would have a dim picture, ALL the back lights, I assume would mean the problem is in power supply itself, which is what all the posts point to. Thanks to all for the help, most educational.

[hartpunch]

Re: Samsung Syncmaster 932B

jetadm123 -Great advice about parting out monitor - I was going to turn it in to E waste - turning it in to dollars is a MUCH better idea. Thanks !

[jetadm123]

Re: Samsung Syncmaster 932B

Ouch! $70 for a transformer?! And there's no guarantee that replacing it will solve the problem. You can buy a fully functioning used monitor on Craigslist for that price (or less). If you buy new, then you might consider parting out the monitor and selling the individual parts (lcd panel, logic board, etc) through Ebay. This will help offset your cost of a monitor.

[retiredcaps]

Re: Samsung Syncmaster 932B

The transformer looked like it was the most straight forward fix and that's $70 on eBay but that's not the problem.

$70 is a total ripoff for the transformer. Depending on the model, some go for as low as $5 for TWO + free shipping.

I may suck it up and buy another monitor - maybe not Samsung this time.

It is up to you. If you decide not to fix it, recycle or sell it on your local kijiji/craigslist for parts.

[hartpunch]

Re: Samsung Syncmaster 932B

Thanks for the feedback, VERY HELPFUL. It's coming down to time and money. The transformer looked like it was the most straight forward fix and that's $70 on eBay but that's not the problem. Who knows how much a back light would cost and finding, ordering and replacing a bunch of caps isn't the way I want to spend my weekend. I may suck it up and buy another monitor - maybe not Samsung this time. Any thoughts on reliability of other brands?

[retiredcaps]

Re: Samsung Syncmaster 932B

ALL caps act the same and none are bulging.

1) "2" seconds to black can be caused by

a) bad caps
b) bad inverter transformer
c) bad ccfl
d) bad ccfl wiring
e) sense circuitry is damaged

2) Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300.

3) If your transformer readings are within 3% of each other, it suggest they are good.

4) That leaves the ccfl lamps or the wiring as the next thing to check. The easiest way to test the ccfl lamps is if you have a spare monitor that can act as a good ccfl. See post #14 section 5

https://www.badcaps.net/forum/showthread.php?t=10419

Note you don't actually have to remove the ccfl from the spare monitor for testing. Just stretch the cable from one monitor to another, but don't let the two touch.

[hartpunch]

Re: Samsung Syncmaster 932B

I have a similar problem to Diablo Rojo, which, reading the posts, seems to be common. Monitor fine until last night, then on for 5-8 seconds then black - no back light, no display. Plugged Monitor into my old PC and problem follows monitor. Looking at the posts for help, I checked the transformer and got about 900 ohms across both the primary and secondary of the transformer mentioned in this post so it appears that's not the problem. There's nothing burned, nothing looks bad, I checked the caps on the board with an ohm meter and they act like caps - putting positive lead on pos side of cap and the resistance goes up, so the cap is charging. ALL caps act the same and none are bulging. I have seen reference to "bad inverter board" in other posts, I assume this power supply board is what they are talking about. I have not fired the board up with the case off, I will need to tack on a couple of wires and run them out the side so I can monitor the 5 VDC.

[Diablo_Rojo]

Re: Samsung Syncmaster 932B

Yet another big THANK YOU to PlainBill. I replaced the transformer and was rewarded with a beautiful bright display and one less monitor in the graveyard.

[PlainBill]

Re: Samsung Syncmaster 932B

OK, upon further review it has been determined that the resistance across one pair is about 1K and the other is open. I have ordered the transformer(about 10 days from China). I will post when I get it installed. Thanks for staying with me on this.

Not a problem. This would be very boring (and dangerous!!!) if everyone knew exactly what I was thinking.

PlainBill

[Diablo_Rojo]

Re: Samsung Syncmaster 932B

OK, upon further review it has been determined that the resistance across one pair is about 1K and the other is open. I have ordered the transformer(about 10 days from China). I will post when I get it installed. Thanks for staying with me on this.

[Wrog]

Re: Samsung Syncmaster 932B

If I may interject, the OP may be doing the test incorrectly:

Measure the resistance between the pins circled in red and between the pins circled in blue.

What Plainbill means here is to read the resistance once across the two red pins, and once across the two blue pins and report the results. The instructions could be misinterpreted to mean measure across one of the red pins to one of the blue pins, etc.

[PlainBill]

Re: Samsung Syncmaster 932B

OK,the plot sickens. I put the test lamps back on thinking there is no way either should work and now one set lights up and stays on. This may be what I experienced on my very first test after bringing it home when it came on for five minutes then went dead. At that time I was not able to set up a connection to see if the display seemed unusually dim. Is there something I can test now that we have it half working? Maybe I am completely confused about the transformer but don't the readings I got of open circuit with the dmm set to the lowest range(400 ohm) indicate that none of the lamps should come on?

That's the problem. The secondary of the transformers should measure about 1K ohm (in this case, about means somewhere between 700 ohms and 1500 ohms.)

PlainBill

[Diablo_Rojo]

Re: Samsung Syncmaster 932B

OK,the plot sickens. I put the test lamps back on thinking there is no way either should work and now one set lights up and stays on. This may be what I experienced on my very first test after bringing it home when it came on for five minutes then went dead. At that time I was not able to set up a connection to see if the display seemed unusually dim. Is there something I can test now that we have it half working? Maybe I am completely confused about the transformer but don't the readings I got of open circuit with the dmm set to the lowest range(400 ohm) indicate that none of the lamps should come on?