Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue light.

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

The yellow drop is flux from the factory.

DMM Diode Check function will test these devices. See datasheets for pinouts. See Google for How to Test Diodes or Transistors with DMM.

Here's a starter:

http://www.allaboutcircuits.com/vol_3/chpt_3/2.html

http://www.allaboutcircuits.com/vol_3/chpt_4/3.html

------------------------------

DZT851 - BZX84C27 - 27v zener - http://search.digikey.com/us/en/prod...STR-ND/1793193

QT851 - MMBT2222AFSCT - http://search.digikey.com/us/en/prod...FSCT-ND/458969

RT852 - 1/8w, 101Ω, 5% thick film, (0805 / 2012 metric) - http://search.digikey.com/us/en/prod...ACT-ND/1180316

Toast

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Thanks for the help Toasty!

With diode test on DMM:
DZT851:
one way = 1.
other way = 708

QT851:
B to E at 2000k Ohms : 10/10
C to E at 2000k Ohms: 270/1

B to C at diode test: 740/1
B to E at diode test: 740/1


Both seem good from what I read. Is this correct?

Just to confirm: Do I only have to replace that one resistor then? (And caps as preventative measure?)

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

As long as the 1 means no reading or the same as the leads not touching together, then I agree.

They don't show it there, but you can use the diode test function for transistors as well. The middle letter in its type designation tells you which lead goes to its base.
In this case, QT851 is an NPN type and that means the P = positive = red.
Then you reverse and read with the black on the base. You should get OL or infinity or at least a large difference "in circuit", with some exceptions. It's all very interpretive at times.

If you have any parts or boards lying around, perhaps you could grab a resistor from them. Even a "regular" one would work as you could just tack solder it in place to test.

Toast

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Reconnected the jumper J830 across the bottom, and tacked on a 100 Ohm resistor to RT852, tested for connectivity.
Unfortunately, same result. >12V on 24V rail which decreases to 0.1V, with SB and PS_ON connected with 3.3K Ohm resistor.

Anything else I can check for? Will clearer pictures of the board be helpful? How about testing more components in that general area?

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

The problem with ordering a new supply is that you are still going to have to recap it.

If it has not been recapped, then do that first. If it still does not work, then you could order a replacement unit and have the caps already for it. Best I could find was ~$65 with shipping for this with an unknown warranty.

Toast

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Fair enough. I'll update the thread if I get around to ordering the caps and installing them. Thanks for the help!

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

If you have questions as to which caps, please post back before ordering.

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

I've been cross-referencing the threads https://www.badcaps.net/forum/showth...t=9343&page=21 and https://www.badcaps.net/forum/showthread.php?t=2280 to figure out which caps are appropriate.

I went back and tested all 12 capacitors in-circuit, they all increase in varying resistance, so I'm not sure any of them are dead. Is this reliable enough to tell? It would be neat to figure out at least how to narrow it down, I'm having a lot of fun learning.

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

An ohmmeter will only confirm that the cap is "working" by taking the charge from your meter, or that it's not internally open or dead-shorted.

An ESR meter will give a much better result in that the cap is doing its job as it should in these PSUs. That device, in conjunction with some others, can give a fairly accurate idea as to the caps actual health. Without the ESR meter, you're guessing.

When it comes to these PSUs, a full re-cap will cost ~$15, and that -includes- the mains cap.

I have a strong suspicion that QT851 is bad after going over my notes. That blown 100Ω resistor is inline with its base. I believe that it's shorted E to C, even though your test doesn't seem to indicate that.

It drives an optoisolator that when turned on, disables the ICM801 (MC33067) PWM controller via pin 10, the fault input.

So, in looking at this again, if you remove the 0Ω chip resistor at JB803, you -should- be able to turn the supply on and have everything work.

It's located, by your pictures, slightly down and right of QT851. Marking is simply "0".
Just follow the collector trace from QT851 to the next component.

Be careful and DO NOT PRY or BEND the resistor. They fracture easily. Two (2) soldering irons in tandem make quick work of getting these loose, safely.

Toast

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

I'll be darned, it works! Outstanding!
I'm very impressed- huge thanks, Toasty!

Is it generally safe to use the monitor without the fault input? Is this (QT851?) something I can fix, and does it matter?
I will replace the capacitors as soon as I've got enough in my account to buy them, hopefully keeping it going for awhile!

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

QT851 is necessary as is the fault detector. If those voltages go askew, it is meant to protect the inverter and the video board. The unit should not be run without that protection in place.

Running as it is, do the 24v and the 5.3v lines read the correct voltages?

Unsolder one end of the 100Ω resistor you tacked in place. Just to its left is DT851.
Measure the voltage from ground to DT851 on the side with the single pin. Report.
Then measure on each pin on the 2 pin side. Again, report.

Toast

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

5.3V measures as 5.4V
24V is 24.4V

Measure the voltage from ground to DT851 on the side with the single pin.
Then measure on each pin on the 2 pin side.

I assumed you needed the inverter on for this so I connected PS_ON and SB with 3.3K resistor and made sure the inverter was plugged into the CCFLs, had to keep the PSU awkwardly connected on top of the assembly.
(100 Ohm resistor disconnected)

DT851 single pin = 4.8V
pin left = 0.55V
pin right = 5.53V

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

bump

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

I'm fairly certain the 27v zener is bad (along with QT851). The voltages on DT851 upper pins should be within a volt or so of each other. The single pin should be less than 2 volts (~1.8v) with that 100Ω resistor out of the circuit.

Do you have a 470Ω resistor (or close) around? One more test to confirm if you do.

(2 - 1kΩ will do too.)

Toast

[robertp]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Sorry for the delay, I got a new DMM (ExTech MN42) and yes, I have a 470 Ohm resistor here. Awaiting further instruction!

[Vhaos]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Hello, I am new to the forum but I have the same issue.
I got Samsung 2493HM. The monitor will not turn on ( just black screen). All caps look good, but I went ahead and replaced all with no results. I have no way to test other components, so I'd like to just buy a new Power Supply. Now, I saw in the beginning of thread a link to this power supply : http://www.iccfl.com/product_info.php?products_id=6573

But, my Power Supply is this: http://www.iccfl.com/product_info.php?products_id=11238

Which one should I get? Thanks for any helpful info =)

[budm]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Are the three 68 Ohms resistors OK? They are close by CN801
See pictures, and more pictures at:
http://s807.photobucket.com/albums/y...msung%20245BW/

[Toasty]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Umm, really should be a new thread as this is for the 245BW model. Even thought the PSU is the same, it just gets confusing dealing with different models.

[Vhaos]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

so which one for me ?

[selldoor]

Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh

Hello, I am new to the forum but I have the same issue.
I got Samsung 2493HM. The monitor will not turn on ( just black screen). All caps look good, but I went ahead and replaced all with no results. I have no way to test other components, so I'd like to just buy a new Power Supply. Now, I saw in the beginning of thread a link to this power supply : http://www.iccfl.com/product_info.php?products_id=6573

But, my Power Supply is this: http://www.iccfl.com/product_info.php?products_id=11238

Which one should I get? Thanks for any helpful info =)

Seems like a silly question to me? The original Poster asked if he could useBN44-00173A in place of the board he had ( BN44-00195A.) Because when the BN44-00173A goes wrong it is usually easier to fix. At the time the vendor CLAIMED that BN44-00173A was fully compatible with BN44-00195A. If you look he no longer makes that claim. In addition this was relative to a 245BW NOT a 2493 HM. I would ask the vendor if it is suitable.

You have to bear in mind that it may not be the power supply that is faulty?