Samsung SyncMaster 204BW

[retiredcaps]

Re: Samsung SyncMaster 204BW

Updated picture w/ measured voltages.

Your voltage regulators are with spec of 1% to their rated values. That is, they are good.

[Ritalin]

Re: Samsung SyncMaster 204BW

Bah.. Might just dump this thing on Ebay

[Ritalin]

Re: Samsung SyncMaster 204BW

So I noticed that a 10uF@50V cap wasn't replaced, probably didn't need, it but I thought "what the heck" and replaced it with a 10uF@100V and hooked the computer back up, and now the blue light doesn't come back on at all. 13V is still coming out of the powers supply... So then I rehooked everything up and after 2-3 times of flipping the switch in the back if finally came back to a solid blue light. Maybe just replace the whole power supply?

I'll probably take apart my 204B in hopes that it has the same connections and see which part is failing.

[retiredcaps]

Re: Samsung SyncMaster 204BW

Now that you have a power LED, if you hookup your working computer displaying your favourite wallpaper, can you see the wallpaper on the lcd by shining a flashlight on it?

[Ritalin]

Re: Samsung SyncMaster 204BW

I haven't hooked it up to anything yet, cause the power button is non-responsive, the second I turn on the LCD from the back power switch, the control board LED is on and if you press the button, nothing happens.

[newbie1]

Re: Samsung SyncMaster 204BW

I haven't hooked it up to anything yet, cause the power button is non-responsive, the second I turn on the LCD from the back power switch, the control board LED is on and if you press the button, nothing happens.

pardon me, if i do not read the whole of your explanation/description.

But the red text above reminds me of my previous thread HP w20,
I am not sure whether it applies to you.
But there are poor solder joint at that HP w20 Photocoupler. Once i swapped them (i have 2 of them anyway), the monitor came back from coma..

[newbie1]

Re: Samsung SyncMaster 204BW

oh! just to add.

in that HP w20, the Photocoupler supplies the control pin of the Topswitch CMOS chip (TOP247YN). I am not saying that your power board is using the same topswitch chip, but maybe you can
1) identify the marking of YOUR Topswitch chip,
2) google the datasheet,
3) see which pin is the control pin
4) & trace the voltage source supplying it.

That was what i did.

[Ritalin]

Re: Samsung SyncMaster 204BW

pardon me, if i do not read the whole of your explanation/description.

But the red text above reminds me of my previous thread HP w20,
I am not sure whether it applies to you.
But there are poor solder joint at that HP w20 Photocoupler. Once i swapped them (i have 2 of them anyway), the monitor came back from coma..

I'm up for anything at this point. And it looks like I only have one photocoupler, so I'll take it out and resolder it.

[Ritalin]

Re: Samsung SyncMaster 204BW

So I took the photocoupler out and found the number, but not making much sense to me? Is there a way to check to see if the part is good? also does it have to be installed a certain way? it says L0634 8179 on the chip.

[newbie1]

Re: Samsung SyncMaster 204BW

i tried googling the part number marking to no avail.

As for me mine is this (EL817)

The readings i took on the GOOD photocoupler are as below,..
Pin 1 (Anode)> 121V (the pin closest to the circular dimple on the marking)
Pin 2 (Cathode)> 121V
Pin 3 (Emitter)> 6.4V (this one links to the control pin of the topswitch, on the one with poor slder joint it reads 0V)
Pin 4 (Collector)> 16.7
All the readings were taken with the black probe on the (-ve) point of the BIG cap.. All the readings were taken at first start-up (mains switch turn on, Power led light up, but no respond)

Have u tried soldering it back & see whether it is still the same? What is the marking on U101?

[alexanna]

Re: Samsung SyncMaster 204BW

^ on all the photocouplers i have looked at, pin #1 and #2 are on the secondary side of the p/s. The correct ground location for those pins would be a plated ground screw

[Ritalin]

Re: Samsung SyncMaster 204BW

i tried googling the part number marking to no avail.

As for me mine is this (EL817)

The readings i took on the GOOD photocoupler are as below,..
Pin 1 (Anode)> 121V (the pin closest to the circular dimple on the marking)
Pin 2 (Cathode)> 121V
Pin 3 (Emitter)> 6.4V (this one links to the control pin of the topswitch, on the one with poor slder joint it reads 0V)
Pin 4 (Collector)> 16.7
All the readings were taken with the black probe on the (-ve) point of the BIG cap.. All the readings were taken at first start-up (mains switch turn on, Power led light up, but no respond)

Have u tried soldering it back & see whether it is still the same? What is the marking on U101?

I'll solder it in now and check voltages, but here is a close up of it and see if you can figure it out what it is :P

Now that I look at it, maybe L0634 817B ?

[pedro]

Re: Samsung SyncMaster 204BW

I'll solder it in now and check voltages, but here is a close up of it and see if you can figure it out what it is :P

Now that I look at it, maybe L0634 817B ?

Yup, that'd be an 817. Typically Sharp PC817. Shouldn't be hard to locate a datasheet. One at http://www.futurlec.com/LED/PC817.shtml

[Ritalin]

Re: Samsung SyncMaster 204BW

Yup, that'd be an 817. Typically Sharp PC817. Shouldn't be hard to locate a datasheet. One at http://www.futurlec.com/LED/PC817.shtml

Thank ya kindly sir! I'm in an area of repair I've never done before.

[Ritalin]

Re: Samsung SyncMaster 204BW

May have screwed up, but checking the photocoupler with just the power supply connected, I got...

Pin 1 (Anode)> -55.4V
Pin 2 (Cathode)> -55.2V
Pin 3 (Emitter)> -36.4V
Pin 4 (Collector)> -38.5V

And the part number for the Topswitch chip is CM0765RC.

[newbie1]

Re: Samsung SyncMaster 204BW

May have screwed up, but checking the photocoupler with just the power supply connected, I got...

Pin 1 (Anode)> -55.4V
Pin 2 (Cathode)> -55.2V
Pin 3 (Emitter)> -36.4V
Pin 4 (Collector)> -38.5V

And the part number for the Topswitch chip is CM0765RC.

Did you measure with the black tip of the DMM to the ground screw on the metal case or the (-ve) lead of the Big capacitor? maybe you should try to put the black tip of the DMM the (-ve) lead of the Big capacitor. the reading is definitely odd.

ok for the IC the closest i can find is this >
FSCM0765RC - Green Mode Fairchild Power Switch (FPS) - Fairchild Semiconductor

what ever you do PLEASE DO NOT MEASURE THE DRAIN PIN (Pin 1)!!.. i did THAT & was fortunate to lose ONLY the DMM.. .. The DRAIN pin, as in the datasheet & highlighted by PLAINBILL to me before, could go up to 600V!!!

you could measure for shorts on the respective pins WITH THE POWER UNPLUGGED, & giving it ~ 1min to discharge..

Did the monitor go into shutdown mode if you leave it plugged?

[Ritalin]

Re: Samsung SyncMaster 204BW

Did you measure with the black tip of the DMM to the ground screw on the metal case or the (-ve) lead of the Big capacitor? maybe you should try to put the black tip of the DMM the (-ve) lead of the Big capacitor. the reading is definitely odd.

ok for the IC the closest i can find is this >
FSCM0765RC - Green Mode Fairchild Power Switch (FPS) - Fairchild Semiconductor

what ever you do PLEASE DO NOT MEASURE THE DRAIN PIN (Pin 1)!!.. i did THAT & was fortunate to lose ONLY the DMM.. .. The DRAIN pin, as in the datasheet & highlighted by PLAINBILL to me before, could go up to 600V!!!

you could measure for shorts on the respective pins WITH THE POWER UNPLUGGED, & giving it ~ 1min to discharge..

Did the monitor go into shutdown mode if you leave it plugged?

I checked from the ground screw, but will try from the big cap. I haven't checked anything on the IC yet. And when I plug the monitor in, nothing happens except the power light staying on solid blue.

[newbie1]

Re: Samsung SyncMaster 204BW

what i meant was..

If you leave it plugged longer (lets say 30min) will it automatically shutdown (meaning not even POWER led is turned on)?..

[Ritalin]

Re: Samsung SyncMaster 204BW

I'll give it a try and see what it does. Give me 30 mins :P

[pedro]

Re: Samsung SyncMaster 204BW

^ on all the photocouplers i have looked at, pin #1 and #2 are on the secondary side of the p/s. The correct ground location for those pins would be a plated ground screw

Indeed. Pins 1 & 2 are the photodiode which is where the secondary voltage is fed back to the SMPS controller chip, so the refence should be the secondary i.e. chassis/ground. Pins 3 & 4 are the phototransistor which is in the PRIMARY side, so the reference there should be (generally) the negative lead of the large cap. Using a secondary meter ref will give you all sorts of AC ripple on top of the DC component you are trying to measure.