Samsung Syncmaster 223BW - dead as a rock

[Scenic]

I've got a little problem child today..
A Samsung Syncmaster 223BW 22" LCD.

Seller said he bought a replacement powersupply and it still won't turn on.
Cracked it open, replaced all the PSU caps (5x Samwha XC 25V 820uF and one Sam Young LXZ 25V 330uF).

PSU is up and running, all voltages are there and within spec, but it's still dead as a rock..

checked the LCD controller board (Codename: Mendel_VE ; Model: BN41-00885B) and all voltages seem to be there (silkscreen marks what voltage is where, with test points.. kinda neat)..

power button also works (1.8V ; 0V when pushed), so it's not a flaky connection.

any ideas what else to check?

i've tested the panel itself in a Samsung 2233BW which had a cracked panel. Works fine, but i can't use the panel for that LCD monitor cause the viewable area is slightly smaller than the bezel, even though both are supposed to be 22" monitors... WTH

[Dgtech]

Re: Samsung Syncmaster 223BW - dead as a rock

Is this stuck in stanby?

Any regulators on the processor board? Different video inputs maybe? Flex the board and check for solder cracks? It sucks when it's down to this but for me, a 22 inch samsung is worth keeping so i'd swap the vid board out if I couldnt find anything.

[Rtech]

Re: Samsung Syncmaster 223BW - dead as a rock

Power Button works but does not turn on....Logic board must be first suspect !!

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

Is this stuck in stanby?

Any regulators on the processor board? Different video inputs maybe? Flex the board and check for solder cracks? It sucks when it's down to this but for me, a 22 inch samsung is worth keeping so i'd swap the vid board out if I couldnt find anything.

not stuck in standby. no LED (or any sign of life for that matter).

tried to find the controller board on ebay.. 1 match from ebay USA, but for a Syncmaster 203T (same controller number).. but i don't think it's worth to pay 1$ + 50$ shipping

all regulators on the LCD controller board seem to be working fine.
(1.8V, 3.3V and 5V up and running)

i'm pretty much running out of options ._.

[PlainBill]

Re: Samsung Syncmaster 223BW - dead as a rock

not stuck in standby. no LED (or any sign of life for that matter).

tried to find the controller board on ebay.. 1 match from ebay USA, but for a Syncmaster 203T (same controller number).. but i don't think it's worth to pay 1$ + 50$ shipping

all regulators on the LCD controller board seem to be working fine.
(1.8V, 3.3V and 5V up and running)

i'm pretty much running out of options ._.

Have you looked for a reset controller on the signal card (controller board, logic card)? Is the crystal working? I have a few other ideas, but a picture sure would have helped...

PlainBill

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

still trying to take better pics.. damn reflections..

http://bambooz.pytalhost.net/badcaps...23BW/front.jpg
http://bambooz.pytalhost.net/badcaps...223BW/back.jpg

edit: on the back of the board, all voltages on the test points match the ones printed next to them

[kc8adu]

Re: Samsung Syncmaster 223BW - dead as a rock

stuck/contaminated button?

[Dgtech]

Re: Samsung Syncmaster 223BW - dead as a rock

I'd look into the DC/DC converter on the right hand side. It is labled 1501-50. Here is a datasheet I found on it.

I'm sure you already checked all surface mount diodes at this point.

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

back to this thing..
the DC-DC converter (IC702 ; top right) is fine. 5.01V out.
the LDOs for 1.8V (IC602 ; top left) and 3.3V (IC601 ; below the biggest lytic) are working too and the voltages are very close to what they're supposed to be (0.01 to 0.02V off at most)

checked all the diodes out of circuit (1 leg lifted up) and they all seem to be ok.

Have you looked for a reset controller on the signal card (controller board, logic card)? Is the crystal working?

how would i test the crystal? i don't have a scope. also what do you mean by "reset controller"?

[alexanna]

Re: Samsung Syncmaster 223BW - dead as a rock

We have been able to repair some of the Acer 19” models by replacing the “reset controller” if memory serves me correctly it’s a small 3 pin device with a “U” designation on the board.
Any way search “Acer reset controller” you should come up with some good reading.

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

thanks. looked some threads up and read through them.
there's only one SOT23 3-legger on this logicboard with a "U" designation, and that's U290 (to the right of the LVDS connector (pic in post #6)). everything else is either "Q" (transistors) or "D" (diodes of some kind)

edit: all that's written on it is "BQ" and a vertical "43", which is the exact same as its neighbour labelled Q402 ()

[alexanna]

Re: Samsung Syncmaster 223BW - dead as a rock

^
Can you read the part number of U290?

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

like i said in my edit, all that's written on it is "BQ" (horizontal) and "43" (vertical). exactly the same as Q402 next to it.

http://bambooz.pytalhost.net/badcaps...23BW/front.jpg

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

bump?
plainbill? anyone..?

[alexanna]

Re: Samsung Syncmaster 223BW - dead as a rock

Carefully try to trace the on/ off siginal,You noticed 1.8V toggling low when you pushed the power button, try to find some point on the board where as you push the power button you notice the 1.8V go low.
As an example just recently I had a monitor that the back light on signal was not making it to the connector on the logic board to the inv/ps,I was able to find the 3.2volts BL on signal on the logic board. The 3.2V went low as the monitor went into a sleep mode, so I knew it was the BL on signal, It was traced to a lytic cap that was bad. If we're lucky maybe we can find a bad cap.

[jetadm123]

Re: Samsung Syncmaster 223BW - dead as a rock

Apparently, Q401,Q402 and U290 are all the same transistor: 2SC2412K. Why they used a "U" designator will no doubt go under as one of the great mysteries of monitor repair.

[lkvee]

Re: Samsung Syncmaster 223BW - dead as a rock

Not sure if this will help because it mentions a different model:

http://orig-10013.itway.cotcdn.net/s..._wont_turn_all

BTW that's a FixYa URL. One solution also mentions resoldering the transformers and the induction coil in addition to replacing the capacitors.

I just got a 2233bw myself, and it's showing similar power problems.

[Scenic]

Re: Samsung Syncmaster 223BW - dead as a rock

the powersupply is working fine. allthough i begin to think it's the wrong model for this monitor.

it has an additional master power switch which the original obviously didn't have (prev. owner crudely made a cut-out for it)
the connector to the logic board fits perfectly, but i noticed one discrepancy..

on the logic board, the last pin (lowest pin of the PSU connector in this picture) is clearly labelled/silkscreened as "+5V" on the top side, and on the bottom side it says "Pin 9: +5V_IN".
on the PSU/Inverterboard however, the corresponding pin is just labelled "ON/OFF"

so.. could it be that this PSU/Inverter board (Model "IP-43130A" ; also labelled "205BW REV0.0 2006.12.18") is simply the wrong model for this monitor, and it's dead because of the missing 5V to the logic board?!
what the hell

as for tracing the powerbutton signal, i've tried that too.
i'm gonna try to take closeups with markings where that trace goes. from what i can tell, it more or less directly goes into the Samsung main controller IC through a couple capacitors and resistors and a 6 leg device labelled "ZD202" below the button board connector (see the pic linked above and earlier in this thread)

it does not seem to go to any 3pin SOT23 device on it's way


edit: by the way.. the 223BW and the 2233BW are completely different models

223BW (with the characteristic silver power button at the front with a blue power-LED circle around it)
http://img520.*************/img520/8872/1000697va9.jpg

2233BW (all buttons on the right side, VERY flimsy stand.. overall a cheapo "design" monitor (with a flower pattern on the back.. wtf))
http://ipon.hu/_userfiles/Image/Terr...AMU/01_big.jpg

[alexanna]

Re: Samsung Syncmaster 223BW - dead as a rock

Isn't this fun, just think if we weren't working on monitors we would probably be sitting in a bar somewhere or sitting on a beach being annoyed by that gal talking on the cell phone

[trapt12]

Re: Samsung Syncmaster 223BW - dead as a rock

Hey

I am currently working on the exact same problem, Syncmaster 223BW, no signs of life at all with the Mendel VE BN41-00885b (even same date as yours 2007.06.13) logic board and thought i would share my experience. When i got the monitor open i found a bulged cap on the PSU board, after replacing all the caps the power works fine (14.5V out) and all the levels on the logic board are also correct but no life.

Scenic, I believe you do have the right board, the +5V_IN is output from the logic board into the PSU board to control the back-light ON_OFF. I tested this by removing Q601 (just to the right of the PSU connector in your pic, after removal the +5V_IN goes from 0V to around 3V) and powering up the board, there is still no signs of life but the back-light is now on.

Sadly i think the problem is with the main logic IC, i have scoped out the crystal and thats working fine (14.35MHz if i remember correctly), the power button goes into the main IC around pin 120 and with my scope i see this switching fine when i use the button. However when i look at the gate of various transistors and other points in the circuit i am yet to see any signs of life coming from the logic ic. Like mentioned earlier it seems a shame to get rid of the monitor because looks like it could be nice to use if i ever get it going, so it might have to get put aside while i look for a new logic board or a second one with a broken screen.

If i find anything else i will let you know. Cheers