Samsung Syncmaster 245BW

[retiredcaps]

Re: Samsung Syncmaster 245BW

A -> B = 1.820K ohms
C -> D = 1.796K ohms
E -> F = 1.792K ohms
G -> H = 1.757K ohms
I -> J = 1.807K ohms
K -> L = 1.788K ohms

Since April 2010, PlainBill changed the 5% variation down to 3%.

Using that then,

1820 x 0.97 = 1765 lower bound
1757 x 1.03 = 1809 upper bound

The outlier to me looks like 1757 given the other 4 readings. However, this is also dependent on the accuracy of your multimeter.

Of course, it could be 1820 as well. While I did take an University level statistics course and somehow passed, my days of doing mean, median, bell curves are over.

More information on the entire subject matter starts with post #19 and #20 at

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

[PlainBill]

Re: Samsung Syncmaster 245BW

I too have the same monitor and it will turn on and stay on but the screen blanks out after several seconds. If I turn it off for a bit and turn it back on it may start displaying video again, but is questionable if it stays on and is getting worst. So like the other two I thought I'd pull it apart and try to get a schematic to repair and came across this wonderful site with experienced people with monitor repair. I have an electrical degree but haven't played with circuit diagnostics for many years.

<SNIP>

A -> B = 1.820K ohms
C -> D = 1.796K ohms
E -> F = 1.792K ohms
G -> H = 1.757K ohms
I -> J = 1.807K ohms
K -> L = 1.788K ohms

<SNIP>

You seem to be having a 'Two Seconds to Black' problem. Two things stand out as possible causes. First, secondary G is slightly low, about 4% lower than the highest. Second, it has been reported that the electrolytic caps on this inverter often fail. I'd replace the caps first.

Edit: Darn!!! You-know-who beat me to it!

PlainBill

[Stebono]

Re: Samsung Syncmaster 245BW

Thanks guys for the quick response, I'll figure out what electrolytic's I need from the inverter board and replace all of them. Since DigiKey is in my state I get quick service so I'll do it tonight and hopefully that will fix it.

Otherwise I may need to replace all three transformers I would guess? If I'm following you correctly.

Again thanks guys!

[PlainBill]

Re: Samsung Syncmaster 245BW

Thanks guys for the quick response, I'll figure out what electrolytic's I need from the inverter board and replace all of them. Since DigiKey is in my state I get quick service so I'll do it tonight and hopefully that will fix it.

Otherwise I may need to replace all three transformers I would guess? If I'm following you correctly.

Again thanks guys!

No. One of the failure modes is shorted turns in a transformer. This has multiple effects. First, since that winding now has fewer turns, it reduces the output voltage. Next, it shunts some of the energy from the primary, further reducing the output voltage, Lastly, sometimes the entire transformer will be destroyed.

To reliably test for shorted turns a 'ring tester' is required, but an adequate job can be done with a DMM. We take the threshold as a 3% variation in resistance. If the transformer is actually bad, all you would have to do is replace that transformer, the other two would be fine. If the variation were larger, or this was a different model monitor, I would have suggested that as the first approach. However, this monitor is known for bad caps on the inverter and the variation is very close to 3%, so I suggested replacing the caps first.

PlainBill

[Toasty]

Re: Samsung Syncmaster 245BW

Whoa! Hold it a minute...

Before you go tearing at the inverter, has the PSU been recapped? Correctly?

That's a more likely failure here than the inverter which pops one of the FETs before anything else. Not the case here as that would be 0 seconds of run time.

Some photos of the back side also under the big transformer and towards the standby/pson and 5.3v output plug.

Toast

[Stebono]

Re: Samsung Syncmaster 245BW

@Toasty,

That is exactly what I did as my first step and it turns out to have fixed the problem for almost $10 bucks worth of quality caps. I did screw up on one cap though that I didn't replace since I thought it was a 2.2uF and turned out to be a 22uF. It was right next to the 2.2uF cap and I could barely see the 2 2uF on it so since it was the same size can I assumed, shame on me, that it was also 2.2uF.

Here is the list of caps, there location, value, and manufacture part#'s I used for my rebuild. The monitor works fantastic now and has ran for several hours without the screen blanking out on me.

Samsung SyncMaster 245BW
========================

Power Supply Board assembly Aluminum Electrolytic Capacitors
------------------------------------------------------------
(1) CP801S  82uF 450WV 105 C Panisonic-ECG EET-ED2W820CA
      (cap requires a hot iron with large tip)
(1) CB853 2200uF  10V 105 C Panisonic-ECG EEU-FR1A222L
(1) CM857 1000uF  10V 105 C Panisonic-ECG EEU-FR1A102L
(2) CM851 1000uF  35V 105 C Panisonic-ECG EEU-FR1V102
  CM852
(1) CM855  470uF  35V 105 C Panisonic-ECG EEU-FR1V471
(2) CP804  10uF  50V 105 C Panisonic-ECG EEU-EB1H100S
  CM814
(1) CB805  2.2uF  50V 105 C Panisonic-ECG EEU-EB1H2R2S
*(1) CB804  22uF  50V 105 C Panisonic-ECG EEU-EB1H220S
(3) CB809  47uF  50V 105 C Panisonic-ECG EEU-EB1H470S
  CB812
  CM806

* Put old cap back in since I screwed up on my cap order and
  thought this was a 2.2uF instead of the actual 22uF

Thank you very much, retiredcaps, PlainBill, & Toasty, for steering me in the correct direction rendering me a good monitor again,

Stevo