Samsung Syncmaster 245BW

[PlainBill]

Re: Samsung Syncmaster 245BW

We are back ! Was busy at work so this monitor had to wait. For those that have not given up I have good news to report. If your 245B monitor problem is not related to QM802 or RB805 and you have a flickering monitor then the following might help you.
I did not have the 82uF, 450V bulk cap or sometimes referred to as the hold-up cap that allows a line dropout of maybe a 1/2 cycle to go by without
you noticing there was a line dropout but decided to remove it today and
measure it. I do not have an ESR meter but do have a cap meter and
surprisingly it measures 0 uF. I was able to find a 270uF, 450V at hand and
installed it on the board at location CP803 and the monitor turned on with no
more flicker ! This 82uF, 450V cap is from "Samwha".
now that the monitor is working correctly I measure a solid 386VDC on this
cap and my power factor meter shows the power factor is 0.97 versus 0.65
when it was flickering. The 24V output is also measuring a steady 24V.

Another success story regarding BAD CAPS.
Thanks to everyone's help here.

Congratulations, and thanks for the update. That cap is part of the PFC circuit and should be a low ESR capacitor.

PlainBill

[retiredcaps]

Re: Samsung Syncmaster 245BW

PlainBill wrote (today, before seeing your swapout of the big cap) ...

https://www.badcaps.net/forum/showpo...79&postcount=3

There are two schools of thought on replacing the large cap. One group says that it rarely fails, so don't bother. The other school notes that 'rarely' is NOT 'never' and asks if saving $5 is worth the risk of having to open the monitor up again?

Boy, if you can see this clearly into the future, go buy a lottery ticket! :-)

Congratulations, and thanks for the update. That cap is part of the PFC circuit and should be a low ESR capacitor.

PlainBill

[PlainBill]

Re: Samsung Syncmaster 245BW

PlainBill wrote (today, before seeing your swapout of the big cap) ...

https://www.badcaps.net/forum/showpo...79&postcount=3



Boy, if you can see this clearly into the future, go buy a lottery ticket! :-)

I can clearly see the future. I can predict many things. At the bank I know I will be right behind the lady who used to work at the bank and wants to discuss her former boss, her 6 Grandchildren, the economy, and the teller's love life while filling out three deposit slips and signing a dozen checks - after she finds her glasses.

At the grocery store I will have the last remaining box of the pasta my wife MUST have. And the bar code won't scan, and the bag boy who is sent to check the price will slip and fall on a broken jar of baby food.

If I buy a lotto ticket none of the numbers I choose will come up. If I use the 'quick pick', the guy who cut ahead of me will use it, and get 5 of 6 numbers.

The only time this helped was the time I deliberately got in the slow line because I KNEW the girl with the 36D's in a bikini top would be getting in line behind me. And it turned out she had onions for lunch - LOTS of onions.

PlainBill

[technicalspecialist]

Re: Samsung Syncmaster 245BW

We are back ! Was busy at work so this monitor had to wait. For those that have not given up I have good news to report. If your 245B monitor problem is not related to QM802 or RB805 and you have a flickering monitor then the following might help you.
I did not have the 82uF, 450V bulk cap or sometimes referred to as the hold-up cap that allows a line dropout of maybe a 1/2 cycle to go by without
you noticing there was a line dropout but decided to remove it today and
measure it. I do not have an ESR meter but do have a cap meter and
surprisingly it measures 0 uF. I was able to find a 270uF, 450V at hand and
installed it on the board at location CP803 and the monitor turned on with no
more flicker ! This 82uF, 450V cap is from "Samwha".
now that the monitor is working correctly I measure a solid 386VDC on this
cap and my power factor meter shows the power factor is 0.97 versus 0.65
when it was flickering. The 24V output is also measuring a steady 24V.

Another success story regarding BAD CAPS.
Thanks to everyone's help here.

I would've thought caps would be he first components you'd've checked/tested judging by the unstable voltages. Glad you managed to fix your PSU in the end anyway.

I have a saying that goes: You always find it in the most obvious place you never looked. I guess that was the case here!

[lucky13]

Re: Samsung Syncmaster 245BW

I did not have the 82uF, 450V bulk cap or sometimes referred to as the hold-up cap that allows a line dropout of maybe a 1/2 cycle to go by without
you noticing there was a line dropout but decided to remove it today and
measure it. I do not have an ESR meter but do have a cap meter and
surprisingly it measures 0 uF. I was able to find a 270uF, 450V at hand and
installed it on the board at location CP803 and the monitor turned on with no
more flicker !

That's a rather flat pancake style cap. Would 270uF be too high? I would suggest maybe 100uF 450V cap as a repalcement.

With your tip, I will repalce mine and see if the flickering goes away on mine...

[Aruba]

Re: Samsung Syncmaster 245BW

I would've thought caps would be he first components you'd've checked/tested judging by the unstable voltages. Glad you managed to fix your PSU in the end anyway.

I have a saying that goes: You always find it in the most obvious place you never looked. I guess that was the case here!

It was not as clear cut. The 5V was rock solid and the 24V was only fluctuating when the load was above 2A or so. With these symptoms
and not having seen a large bulk cap reduce its capacitance by more than 50% ever before it was not an obvious place to look. It was only through
persistance that the 24V was fixed and secondly that is is a nice big 24"
monitor. I couldn't see this monitor sitting in a corner collecting dust.
Oh I also liked your saying, so appropriate !

[Aruba]

Re: Samsung Syncmaster 245BW

That's a rather flat pancake style cap. Would 270uF be too high? I would suggest maybe 100uF 450V cap as a repalcement.

With your tip, I will repalce mine and see if the flickering goes away on mine...

Yes the 270uF cap I replaced the 82uF cap with was a little too big. It
was however only for me to confirm that the problem was with the bulk
capacitor. When I assembled it back together I actually used a 100uF, 450V
cap even though it was slightly taller it still fitted perfectly in the space.
Hope this cap replacement will fix your monitor as well. If not you can post
your findings and we will see if we can help.
I am using the 245BW monitor now to type this message. I have asked my
collegue if I can use it to "run in" the monitor so to speak after it has been
fixed. So far so good. I have it set at the max 1920X1200 resolution and it
looks great, the picture on it looks very sharp. I am going to hate it
when I have to give up this monitor and go back to my regular 20".

[lucky13]

Re: Samsung Syncmaster 245BW

Yes the 270uF cap I replaced the 82uF cap with was a little too big. It
was however only for me to confirm that the problem was with the bulk
capacitor. When I assembled it back together I actually used a 100uF, 450V
cap even though it was slightly taller it still fitted perfectly in the space.
Hope this cap replacement will fix your monitor as well. If not you can post
your findings and we will see if we can help.

Hey Aruba, you are THE MAN!

I pulled a 120uF/400V cap from a dud board and replaced the 82uF on the Samsung and it works! No more flickering. I will leave it burn-in for awhile while I look for a not too cap from my junk pile that will fit there (I am too cheap to order just one from Digikey).

[PlainBill]

Re: Samsung Syncmaster 245BW

Hey Aruba, you are THE MAN!

I pulled a 120uF/400V cap from a dud board and replaced the 82uF on the Samsung and it works! No more flickering. I will leave it burn-in for awhile while I look for a not too cap from my junk pile that will fit there (I am too cheap to order just one from Digikey).

I understand the need to 'conserve financial resources', but that cap must be low ESR. It's part of the PFC 'front end' and gets a lot of stress.

PlainBill

[lucky13]

Re: Samsung Syncmaster 245BW

I understand the need to 'conserve financial resources', but that cap must be low ESR. It's part of the PFC 'front end' and gets a lot of stress.

PlainBill

Noted. I meant to yank one out from a dud board after confirming it is not a crappy brand and the capacitance & ESR are in-check, instead of ordering a new one. I recall I had seen a Rubicon somewhere in my pile...

[lucky13]

Re: Samsung Syncmaster 245BW

I just checked the old cap with my McroESR and it says 0uF and 0 ohm in ESR.

How can that be?

I measured the repalcement cap I subbed in (120uF 400V) and it measures 116uF and 1.1ohm ESR.

[PlainBill]

Re: Samsung Syncmaster 245BW

I just checked the old cap with my McroESR and it says 0uF and 0 ohm in ESR.

How can that be?

I measured the repalcement cap I subbed in (120uF 400V) and it measures 116uF and 1.1ohm ESR.

It's either open (more likely) or shorted and the MicroESR doesn't handle extremely high ESR readings properly.

PlainBill

[Aruba]

Re: Samsung Syncmaster 245BW

It's either open (more likely) or shorted and the MicroESR doesn't handle extremely high ESR readings properly.

PlainBill

Hi Bill,
I don't have an ESR meter or I could try this but could it be by default that
when the meter reads 0uF the meter displays 0 ohms ?
What does the meter read for ESR when one measures a 2 inch 20GA wire
(basically a short) ?

[PlainBill]

Re: Samsung Syncmaster 245BW

Hi Bill,
I don't have an ESR meter or I could try this but could it be by default that
when the meter reads 0uF the meter displays 0 ohms ?
What does the meter read for ESR when one measures a 2 inch 20GA wire
(basically a short) ?

I don't have a MicroESR, I've got a Bob Parker Blue ESR meter. When presented with a 2" length of wire it reads .01 ohms. Of course, it doesn't have a capacitance range.

PlainBill

[Tex]

Re: Samsung Syncmaster 245BW

Can anyone identify the marking codes on part QM801 (close to F9222L on bottom of PS board - in between a B3 diode & Y10 zener). This part is physically damaged and I cannot identify it. Thanks.

[lucky13]

Re: Samsung Syncmaster 245BW

Looks to be ZH (05).

Need a close-up picture?

[Tex]

Re: Samsung Syncmaster 245BW

Thanks Lucky13 - I'd like that close-up if possible (although ZH makes sense as I see some other transistors marked ZG on the board).

[Aruba]

Re: Samsung Syncmaster 245BW

Can anyone identify the marking codes on part QM801 (close to F9222L on bottom of PS board - in between a B3 diode & Y10 zener). This part is physically damaged and I cannot identify it. Thanks.

QM801 is specified as a KST2907 general purpose PNP SOT23 transistor.
Part is available at Mouser.

Aruba

[Tex]

Re: Samsung Syncmaster 245BW

Stewart710 :

Did you ever get your 245BW fixed ? The one I'm working on exhibits the exact symptoms as yours. Blue power light on but no 24v or 5.3v. Voltages on the 9222L look good except pin 11 is 4.5v (compared to 1.26v as measured by Aruba). Replaced several power sup. caps even though none looked bad to no avail. The resistor and transistor talked about by others on the thread test fine on my unit. I replaced a PNP transistor that was physically damaged (during removal - not burned during use) but still I only get the blue light. Any luck finding the problem on yours ?

[Aruba]

Re: Samsung Syncmaster 245BW

If you getting a steady 390V on pin 23 of the F9222L controller it means you PFC is
working correctly. The problem is then with the F9222L controller which is used to
develop the 24V output. The 5.3V output is developed from the 24V. If you don't have
the 24V output you will not get a 5.3V output.
A good place to start is to measure all the transistors, diodes and resistors connected
nearby the F9222L controller. Make sure they are not shorted or open and the resistors
are still of the correct value as marked on their bodies.