Samsung Syncmaster 245BW

[WiseguyTom]

Re: Samsung Syncmaster 245BW

I had the same problem with my syncmaster 245B (which has a BN44-00195A power supply).
Blue light came on but no image on the screen.

I was able to fix it and want to share my experiences.

At first, the problem was intermittent.
Sometimes an image was displayed and then suddenly it went black again.
Hitting the back or side of the screen a few times, often brought back the image.
But I had to hit it harder and harder to get the image back and after a few weeks I deciced to have a look inside.
After visual inspection I saw nothing special, no bad capacitors or resistors.
Also the fact that hitting it often/sometimes brought back the image made me believe it's not caused by an electronic component but by something else.
But what? A bad or loose transformer was my first guess.

I took out a DVM and started measuring on the stand-alone power board.
Standby 5.2V was ok. Connected it to the Pwr-On line to activate the other output voltages.
Nada, no 24V.

Then I started bending the PCB, pulling up one side while holding down the middle.
Don't do this with you bare hands or you'll get electrocuted!
All of a sudden, the 24V appeared!

Then I stumbled on this blog:
http://blog.whitesites.com/How-to-Fi...97265_blog.htm

Here they mention soldering joins that went bad.
So I re-soldered all big end medium joints and that did the trick.

So get your soldering iron out guys!

Cheers,
Tom

[AlexHan]

Re: Samsung Syncmaster 245BW

I had a long time problem of hi pitched buzzing when moving the mouse. After a year of the buzzing the monitor went kaput. Replaced RB805 and everything was fine again, no buzzing. The replaced resistor looked fine but was completely open. Just wanted to add my experience and say thank you to everyone! Saved another monitor!

[Melej]

Re: Samsung Syncmaster 245BW

Hi, i have read till page 33, if some one can help...

the volt on big cap 82 uF is 150volt, I assume the voltage from the bridge is correct (150v) but i can't figure it out how they duplicate the voltage?
what could be wrong?
Plus this plasma works some times beautifully and then when i turn it off stay off, and not response.
any suggestion?
I am suspecting a crack some where or bad soldering spot, but not found yet.
thank you.

[technicalspecialist]

Re: Samsung Syncmaster 245BW

Is your mains supply 120V US or 240V europe.

[budm]

Re: Samsung Syncmaster 245BW

@melej: What is your board P/N? BN-XXXXX?????? 245 uses more than one version of the power supply board.

[Melej]

Re: Samsung Syncmaster 245BW

Hi, thank for your concern, I'll answer tomorrow.

thank you.

[pyraxiate]

Re: Samsung Syncmaster 245BW

Just wanted to drop a quick thanks. I have 2 245bw's and 2 weeks ago one went out. Rather than trying to use my cheapo 30 watt ratshack iron, I waited and ordered a ratsjack temp controlled station. It did a much better job. I lifted the 2 pads which run the 3 resistors in parallel. Luckily the important pads didn't get damaged. I was able to solder bridge the 2 center pins joining the resistors and all went well. I replaced them with much larger 3 watt resistors. At .69 cents USD each it was worth waiting on them.

[pyraxiate]

Re: Samsung Syncmaster 245BW

Forgot to post pics LOL. Sorry here they are

[pyraxiate]

Re: Samsung Syncmaster 245BW

It also appears this forum doesn't allow you to add / edit your reply.... Sorry for the multiple posts in a row. I did notice that the monitor I replaced the blown resistor in runs a bit warmer on the back for some strange reason. I may add a couple 12V fans to both screens later.

One more thing to note. On the first photo I posted showing the original resistors, none looked visibly blown. I had to take out my multimeter ( yes analog..... dont ask... I just prefer them LOL ). The brown stuff in the photo is just the factory glue which I had to separate. Definitely check rb805 806 and 807 manually. I replaced all 3 and as others have posted... there's TONS of free room to add higher watt resistors.


Thanks again everyone and good luck to you all =)

[budm]

Re: Samsung Syncmaster 245BW

Good job, just make sure to remove ALL the glue, otherwise the wires and leads of the component will be damaged, the glue is also conductive which will cause shorted circuits.
BTW, those 68 Ohms resistors are connected in series.

[sky007]

Re: Samsung Syncmaster 245BW

Need help here.

Got a monitor from my friend. Power supply is BN44-00195A. It gets 2 fuse blown, NT801S blown as well. After some work, cleared up all bad glue, found QP801S blown as well, replaced QP801S. I do not know what NT801S is, just found one NTC thermistors from a old computer power supply. Now connect all the boards together, I can see the blue power LED blinking, but I can't turn it on. Measure the main board connect, only SB give the 5.2V. Checked PFC, it is 155V only.

What else should I check? Thanks.

[pyraxiate]

Re: Samsung Syncmaster 245BW

Good job, just make sure to remove ALL the glue, otherwise the wires and leads of the component will be damaged, the glue is also conductive which will cause shorted circuits.
BTW, those 68 Ohms resistors are connected in series.

As far as the glue goes, I replaced all 3 resistors No more glue. I meant to say series vs parallel. My apologies there and thanks for catching it for me. Running the multimeter across all 3 shows more resistance vs less resistance which running in parallel would so. I posted the first post on my cell and I didn't read before hitting submit lol.

[pyraxiate]

Re: Samsung Syncmaster 245BW

Need help here.

Got a monitor from my friend. Power supply is BN44-00195A. It gets 2 fuse blown, NT801S blown as well. After some work, cleared up all bad glue, found QP801S blown as well, replaced QP801S. I do not know what NT801S is, just found one NTC thermistors from a old computer power supply. Now connect all the boards together, I can see the blue power LED blinking, but I can't turn it on. Measure the main board connect, only SB give the 5.2V. Checked PFC, it is 155V only.

What else should I check? Thanks.

Check rb805/6/7 ? Don't go on visual inspection alone. Make sure they all read 68 ohms. 805 was blown on mine but I couldn't tell until I ohmed it out. My blue power button also blinked with no picture.

[re-atari]

Re: Samsung Syncmaster 245BW

Check rb805/6/7 ? Don't go on visual inspection alone. Make sure they all read 68 ohms. 805 was blown on mine but I couldn't tell until I ohmed it out. My blue power button also blinked with no picture.

His PSU is a 00195A, a completely different design that doesn't have the 3 resistors with the (always) failing RB805. The PSU is probably from a 245B Plus, but is also used in HM2493's.
For the 3-resistor 00137A PSU, your advice is spot on.

re-atari

[sky007]

Re: Samsung Syncmaster 245BW

His PSU is a 00195A, a completely different design that doesn't have the 3 resistors with the (always) failing RB805. The PSU is probably from a 245B Plus, but is also used in HM2493's.
For the 3-resistor 00137A PSU, your advice is spot on.

re-atari

Correct, my is 195A.

[pyraxiate]

Re: Samsung Syncmaster 245BW

Correct, my is 195A.

Since the symptoms are similar, I'd still probably focus on the PSU. Have you tested things with a meter? Its time consuming to troubleshoot and I looked online elsewhere with no luck for you. If you do find a bad resistor or cap, please post back.

[budm]

Re: Samsung Syncmaster 245BW

Need help here.

Got a monitor from my friend. Power supply is BN44-00195A. It gets 2 fuse blown, NT801S blown as well. After some work, cleared up all bad glue, found QP801S blown as well, replaced QP801S. I do not know what NT801S is, just found one NTC thermistors from a old computer power supply. Now connect all the boards together, I can see the blue power LED blinking, but I can't turn it on. Measure the main board connect, only SB give the 5.2V. Checked PFC, it is 155V only.

What else should I check? Thanks.

The PFC IC controller ICP801S (FAN7530?) is probably bad also (the PFC MOSFET was already blown) since you are not getting the Boosted voltage, need to check the Gate drive resistors and Diode to make sure they are not damaged also.

[sky007]

Re: Samsung Syncmaster 245BW

The PFC IC controller ICP801S (FAN7530?) is probably bad also (the PFC MOSFET was already blown) since you are not getting the Boosted voltage, need to check the Gate drive resistors and Diode to make sure they are not damaged also.

I was suspect the same thing. Either no VCC for PFCIC which is M_Vcc power by QB801, or boost circle problem. Can you tell M_Vcc reading when power on?

Also I test all components around ICP801S, looks like something wrong with DP803. Using multimeter, switch to diode, get the same reading on both side. Does it suppose one side no read?

Sorry my bad English.

[budm]

Re: Samsung Syncmaster 245BW

If you look at the spec of the PFC IC, the startup voltage at VCC pin is 12V, the recommending running voltage is 20V. You should check and see if there is resistor/diode network between the Gate drive output pin and the Gate of the PFC MOSFET, check them out to see if they are damaged, I usually replace the MOSFET and the IC at the same time.
The transistor that feeds the VCC pin of the PFC IC and the 24V SMPS IC is setup as a linear voltage regulator to put out about 15~20VDC, the voltage feeding the transistor is from rectified and filtered from the AUX winding of the STBY power supply transformer, this transistor is turn on by the PS_ON signal from the main logic board.

[sky007]

Re: Samsung Syncmaster 245BW

If you look at the spec of the PFC IC, the startup voltage at VCC pin is 12V, the recommending running voltage is 20V. You should check and see if there is resistor/diode network between the Gate drive output pin and the Gate of the PFC MOSFET, check them out to see if they are damaged, I usually replace the MOSFET and the IC at the same time.
The transistor that feeds the VCC pin of the PFC IC and the 24V SMPS IC is setup as a linear voltage regulator to put out about 15~20VDC, the voltage feeding the transistor is from rectified and filtered from the AUX winding of the STBY power supply transformer, this transistor is turn on by the PS_ON signal from the main logic board.

Just checked resistor/diode network between the Gate drive output pin and the Gate of the PFC MOSFET, they looks good.

Using a 330k resistor connect Sb and PW_On, so I have PSON 3V single. It switch on QB851, so PC801S and PC802S on.
I ahve trouble now, the ICP801S (PFC IC) Vcc is 1V only which should above 15V. And the Vcc on IC801S (SMPS IC) is 14V.

Checked around components, look good. My question is, if PFC IC is damaged, will it cause Vcc pin low voltage?

Thanks.