Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
@Toasty: Still have a test for me to do?
robertp
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Last Activity: 04-07-2012, 03:13 PM
Joined: 02-09-2012
Location: SF Bay Area
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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!Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
bumpLeave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
5.3V measures as 5.4V
24V is 24.4V
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...Last edited by robertp; 02-14-2012, 11:51 PM.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
I'll be darned, [b][i]it works![/i][/b] 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!Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
I'll be darned, [b][i]it works![/i][/b]Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
I've been cross-referencing the threads [url]https://www.badcaps.net/forum/showthread.php?t=9343&page=21[/url] and [url]https://www.badcaps.net/forum/showthread.php?t=2280[/url] 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.Re:...Leave a comment:
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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!Leave a comment:
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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?Last edited by robertp; 02-13-2012, 02:50 PM.Leave a comment:
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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?)Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
DZT851 has a bubble of magic yellow goop hanging off the side, QT851 looks physically OK to me. Any way to test these?...Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
The jumper is underneath the heatsinks the MOSFETs are screwed to, and there is another component blocking the screw... I pushed it up through the bottom but I'll probably connect it back across the bottom rather than unsolder a bunch of other stuff to get to the screw.
My multimeter only goes down to 200 Ohms and all those tiny resistors all flash ~50-150ish and then shows "1 .", RT852 has the same result as the others.
The prismatic split is from taking...Last edited by robertp; 02-12-2012, 09:37 PM.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
@Toasty: It is indeed constant 24V. Now to figure out how to reconnect the jumper!
@PlainBill: I did the capacitor tests in-circuit so far, I'll take them out if it sounds like it'll help narrow it down. I'm not too great with a soldering iron so I'm afraid to mess up the board too much.
Last edited by robertp; 02-12-2012, 07:52 PM.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
Here are alternates just in case something isn't readable, hope I got the right section....Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
Without the inverter connected (with PS_ON and SB connected with 3.3K resistor) the 24V rail gave me >12V which quickly decreased to 0.1V (only after a cold start), and the large black capacitor gave me ~385V.
[i]With[/i] the inverter connected (with PS_ON and SB connected with 3.3K resistor) I got the same results for both 24V rail and 385V capacitor.
Both measurements were with the video board disconnected.
Does this tell you anything?
I...Last edited by robertp; 02-12-2012, 02:53 PM.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
Thanks Bill!
I connected the SB to PS_ON and tested 24V, got 0.1V.
The voltage at the large blue capacitor was 1V, I think.
Seems like it's the PSU. Without being able to test the caps properly (and since it seems the MOSFETs are probably bad too) I'll just go ahead and order a new board in the next couple of days, unless anyone advises against it.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
That's great, thanks for finding that!
If we can determine whether it is the PSU that needs replacing I will just buy that, since this particular PSU seems more difficult to troubleshoot.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
CM812 (lower left) was the one I marked with a black marker, which is why it looks strange in the picture. It is not bulging and appears OK, (inaccurate) testing with a multimeter gives the same response as the others, with Ohms set to 20K it increases from 0 to 0.66 and slowly increases from there.Leave a comment:
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Re: Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue ligh
Reading that thread now.
I should mention the "flashlight test" shows no image, and the blue light does not turn amber or go into sleep mode.
I'll take some pics of the bottom of the boards later today if I can.
In case it helps before then: the PSU bottom is identical to previously posted pictures, all traces, no components.
The inverter is the "strange one" with all the traces on the top side, the bottom is blank.Leave a comment:
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Yet Another Samsung 245BW - Power Board BN44-00195A - No display, solid blue light.
I read all of these previous threads:
[url]https://www.badcaps.net/forum/showthread.php?t=15796[/url]
[url]https://www.badcaps.net/forum/showthread.php?t=9425[/url]
[url]https://www.badcaps.net/forum/showthread.php?t=6930&page=24[/url]
[url]https://www.badcaps.net/forum/showthread.php?t=15843[/url]
and a few more that were less relevant.
Admittedly, I barely know what I'm doing here but I tried my best to understand the threads.
It seems the results were bad MOSFETs, bad inverter, and maybe the long blue high voltage capacitor(?)....Last edited by robertp; 02-11-2012, 02:27 PM.
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