Getting started with troubleshooting [Samsung 245BW]

[nerdbot]

Re: Getting started with troubleshooting

If you need further help identifying the correct pins, please provide better pictures of the connector areas of the power supply.

I've taken a few more pictures:
power-logic-connected.jpg - A picture of what I had connected for the tests, just to make sure I understood you correctly.
powerboard-power-pins.jpg - Closer view of the power board pins
logicboard-power-pins.jpg - Closer view of the logic board pins

Turning the main supply on also turns on a PFC front end. Also, the board shows signs of moderate overheating.

Which board is showing signs of overheating? I'm assuming you mean the logic board since those pins are looking brownish.

One of the lines (pins) should be labeled 5VSB or something similar. Other pins will be labeled Gnd. With the monitor connected to power, measure the voltage between Gnd and 5VSB.

I saw what appears to be an S_B pin (just to the left of the PSON pin), and I tested that voltage and, depending on how steady my hands were, between 3.5V and 4.3V.

Because I wasn't sure if S_B was the right pin to be testing, I also tested the three 5.3V pins. Those all read 0V.

If 5VSB is present, look for a pin labeled PSON, On/Off, or something similar. Measure the voltage from Gnd to that pin. Does the voltage change when you press the power button?

The PSON pin measured between 0.6V and 1.4V. I noticed though that if I had a voltage over 1.0V, it would often slowly decrease until it reached 0.6V or 0.7V.

When I connected the cable that leads to the buttons on the front bezel, and pushed the power button, I noticed at most a 0.1V drop, but I wasn't sure if that was from my unsteady hands, the decreasing voltage behavior I mentioned above, or what. Pressing the power button repeatedly did not cause the voltage to go down any further, nor would it go back up 0.1V. I tried to wait until the PSON voltage stabilized before pressing the button, but it was a little difficult holding the leads with one hand, pressing the button w/ the other, and staying steady enough to read the DMM. If you like, I can try it again when my wife gets home to help me out.

If 5VSB is not present, check the voltage across the very large cap in the center of the board. That should read either 165 volts or something like 380 volts. If that voltage is missing, check the two fuses.

I tested it anyway, it measured at 160V.

Connect everything to get a "load" on the power supply.

I didn't connect everything, because as you correctly noticed, I'm new to this and wanted to start out with the simpler setup first. But, if you think the results below warrant more tests with everything connected, I can certainly do that.

1) Put your multimeter on 20V DC.
2) Put your black probe on a ground screw on the logic board.
3) Put your red probe on each pin on connector CN700. Use a steady hand and do not let the red probe slip and touch 2 connector pins because that might cause a short.
4) Report each pin and its voltage measurement. Some will be 0, and others should be 5V DC.

Going from top to bottom:

NC: 0V
NC: 0V
+5V_IN: 0V
+5V_IN: 0V
+5V_IN: 0V
GND: 0V
GND: 0V
GND: 0V
NC: 0V
NC: 0V
NC: 0V
GND: 0V
GND: 0V
GND: 0V
5.2V_ST: Ranged between 3.5V and 5.2V
POWER_EN: 1.41V

Anyway, we are both saying esentially the same thing, but his response covers A to Z, while mine is more "step by step" one at a time and deliberately slower because I sense you are newbie at using your multimeter (I was in your shoes recently).

Definitely appreciate it, you are right, this is my first time working w/ electronic components.

Thanks again for the advice guys!

[PCBONEZ]

Re: Getting started with troubleshooting

An ESR meter checks the AC 'resistance' of a cap.
It's test voltage is [usually] 100kHz.
The purpose is to know how well the cap is handling Ripple which is a random AC [usually] at about 100kHz.

A DMM can only check DC resistance because it's test voltage is DC.
Still somewhat useful with caps because you can find completely open or completely shorted caps but it will miss caps that are shot insofar as their AC properties which is how most caps fail and/or a sign the cap is seriously degraded.
.

[retiredcaps]

Re: Getting started with troubleshooting

It looks like PlainBill and I were composing responses at the same time, but his ISP beat mine. :-)

Anyway, we are both saying esentially the same thing, but his response covers A to Z, while mine is more "step by step" one at a time and deliberately slower because I sense you are newbie at using your multimeter (I was in your shoes recently).

Note that measuring the main filter capacitor involves high voltage so be careful.

PS. Since responses are already present in this thread, don't tack onto to the other 245BW threads. Keep everything here.

[retiredcaps]

Re: Getting started with troubleshooting

1.) The DMM I have should be sufficient for measure voltages, and is what I'll need for testing that there is voltage present between various components

Yes, the Greenlee multimeter is much better than those generic 830 made ebay junk and is more than sufficient to measure voltage.

2.) An ESR is for diagnosing specific capacitors

An ESR tester measures the equivalent series resistance (ohms) of a capacitor. While nice to have, it is not a requirement.

the power board is the one that has the power switch and power cable connector, and the logic board is the one with the DVI and VGA ports?

Correct.

If so, can I just connect those two together to test for voltage, or do I need to connect everything together (power board to inverter board, logic board to LCD panel, etc)?

Connect everything to get a "load" on the power supply.

And how exactly would I test for voltage between those two boards (i.e., which pins would I use)?

1) Put your multimeter on 20V DC.
2) Put your black probe on a ground screw on the logic board.
3) Put your red probe on each pin on connector CN700. Use a steady hand and do not let the red probe slip and touch 2 connector pins because that might cause a short.
4) Report each pin and its voltage measurement. Some will be 0, and others should be 5V DC.

[PlainBill]

Re: Getting started with troubleshooting

Pretty good pictures, but there is a slight problem. The legends on the bottom aren't quite clear enough to read. I'll describe what I need, then you can take it from there. If you need further help identifying the correct pins, please provide better pictures of the connector areas of the power supply.

This is a common type of power supply used in larger monitors. It is actually a dual supply. The standby supply normally produces 5 volts whenever the power cord is plugged in. There is a control line from the signal board (logic board) that turns the main supply on. Turning the main supply on also turns on a PFC front end. Also, the board shows signs of moderate overheating.

For the first test, all you will need are the power supply and the signal card hooked together; disconnect the cable that runs to the inverter. The first test is on the connector from the power supply to the signal card. One of the lines (pins) should be labeled 5VSB or something similar. Other pins will be labeled Gnd. With the monitor connected to power, measure the voltage between Gnd and 5VSB.

If 5VSB is present, look for a pin labeled PSON, On/Off, or something similar. Measure the voltage from Gnd to that pin. Does the voltage change when you press the power button?

If 5VSB is not present, check the voltage across the very large cap in the center of the board. That should read either 165 volts or something like 380 volts. If that voltage is missing, check the two fuses.

EDIT: The 'solenoid' is an inductor. Check the leads for cracked solder joints.

PlainBill

[nerdbot]

Re: Getting started with troubleshooting

I forgot to mention, when I noticed the monitor wasn't turning on, I smelled the back grill and detected a an electronic burn smell. In A-front.jpg, I highlighted a solenoid(?) in the lower right hand corner that had a faint electronic burn-type smell to it. None of the other components seemed to have a noticeable smell. Not sure if that means anything or not.

[nerdbot]

Re: Getting started with troubleshooting

Thanks for the reply guys. So, just so I understand -

1.) The DMM I have should be sufficient for measure voltages, and is what I'll need for testing that there is voltage present between various components

2.) An ESR is for diagnosing specific capacitors (assuming it isn't obvious what's wrong from other tests)

So I guess the next thing for me to do is to test that voltage is present between the power board and logic board. I believe I know which is which - the power board is the one that has the power switch and power cable connector, and the logic board is the one with the DVI and VGA ports? If so, can I just connect those two together to test for voltage, or do I need to connect everything together (power board to inverter board, logic board to LCD panel, etc)? And how exactly would I test for voltage between those two boards (i.e., which pins would I use)?

I've attached pictures of the 3 boards I can see, and I'd just like to make sure I've identified them properly:

A-front.jpg and A-back.jpg is the front and back of the power board.
B-front.jpg and B-back.jpg is the front and back of the logic board.
C-front.jpg is the front of the inverter board (the back is empty).

Thanks again!

[jetadm123]

Re: Getting started with troubleshooting

The 245BW is pretty well documented on this site and it seems that problems for this monitor are narrowed down to bad caps or bad resistors.

Another great tool for troubleshooting is the "search" function located in the above toolbar. You're already ahead of the game, since you've taken the time to read some of the threads. There's one thread that spans 15 pages! You definitely get the gold star if you can stomach reading through it all. However, there's great info and it's likely you'll solve the problem using that info.

If you still have problems, then as mentioned above, post some photos and provide a good description of the symptoms and we'll go from there.

[PCBONEZ]

Re: Getting started with troubleshooting

I agree...

An ESR measures Ohms, yes, but it measures it using [in our case] a 100kHz test signal.
A DMM measures it with DC.
.

[retiredcaps]

Re: Getting started with troubleshooting

Now, I'd like to start troubleshooting the issues w/ my 245BW - the power button doesn't even light up.

The power LED not lighting up could also be a sign of bad capacitors. Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300.

Will I need an ESR meter?

Replacing all your caps is probably less than $10 while a low end ESR meter is $50. So unless you are doing a lot of repairs, the economics don't justify the purchase of an ESR meter.

Also, I see people advising to measure voltages and resistances of various circuits. Am I correct in assuming that this is done w/ the monitor opened up, but everything still connected and w/ power on?

Yes. Since there is no power LED, you will be asked to see if there is secondary voltage present between the power and logic board using your multimeter. The logic board needs probably 5V DC to enable the power LED. Resistance is ALWAYS measured with power OFF and lcd unplugged.

Once I'm ready, should I post my issue in there or should I start a new thread? Not quite sure what the etiquette is here.

Either tacking on or starting a new one is okay here. Each has its pros and cons. Make a decision and keep it in one thread so people are not confused.

[nerdbot]

Hi all,

I have two dead monitors right now, one is a Samsung Syncmaster 245BW that died mysteriously last night and was a replacement for my first dead monitor, a Samsung Syncmaster 204B.

The 204B has the flickering issue, and about a year ago I had found all the howtos for replacing the capacitors on the power board, but I never got around to actually fixing it. That is, until last night when my 245BW died. The 204B has now been disassembled, and I see the tell-tale bulging capacitors and I will be having a friend (who is handy w/ a soldering gun) help me replace them shortly.

Now, I'd like to start troubleshooting the issues w/ my 245BW - the power button doesn't even light up. I see there are other threads already about similar issues w/ the 245BW, so I want to try the existing suggestions/tests to make sure the solution to my problem hasn't already been discussed. However, as I read through the threads I realize I'm in a bit over my head.

So, I wanted to make sure I had the right tools and get some basics down before I got started. I have a multimeter (attached a picture), but I see people mentioning an ESR meter. From what I gather, it's designed to measure much lower values than most multimeters can measure? Will I need an ESR meter?

Also, I see people advising to measure voltages and resistances of various circuits. Am I correct in assuming that this is done w/ the monitor opened up, but everything still connected and w/ power on?

Finally, I see there's a 245BW thread already. Once I'm ready, should I post my issue in there or should I start a new thread? Not quite sure what the etiquette is here.

Thanks!