Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Computer Displays
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 01-01-2011, 06:23 PM   #21
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

From your photo, pins 7 and 8 of the Z1010A are connected together and are connected to one end of the coil (the plastic rod with copper wire wound around it). Measure the voltage at the other end of this coil.

Secondly, measure the voltage at the 8-pin connector of the power board for the on/off pin. Measure once before you push the on/off button and once after you've pushed the button. It will be good if you can have your positive probe connected at all times while you press the on/off button.

Last edited by jetadm123; 01-01-2011 at 06:27 PM..
jetadm123 is offline   Reply With Quote
Old 01-02-2011, 04:24 AM   #22
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Okay, the coil says 1.76V on the opposite side. When I held the probe, it sometimes said 1.78V, but it was pretty stable on 1.76V. I measured by trying to hit the solder joint on the PCB where the wire from the coil was joined.

I measured the ON OFF pin, and imediately after I switch the flip on the power supply board, it says 0.03V on it. I measured it while pressing the POWER button on the front, but nothing happened, the output was still 0.03V.

So I guess that tells us that the logic board doesn't ask the power supply board to start?
reneg is offline   Reply With Quote
Old 01-02-2011, 10:52 AM   #23
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
Okay, the coil says 1.76V on the opposite side. When I held the probe, it sometimes said 1.78V, but it was pretty stable on 1.76V. I measured by trying to hit the solder joint on the PCB where the wire from the coil was joined.

I measured the ON OFF pin, and imediately after I switch the flip on the power supply board, it says 0.03V on it. I measured it while pressing the POWER button on the front, but nothing happened, the output was still 0.03V.

So I guess that tells us that the logic board doesn't ask the power supply board to start?

Looks like the Z1010A is ok. You are correct about the power board not getting the signal to start (as PlainBill mentioned back on post #12). With power off and monitor unplugged, I suggest you check the pushbutton board. With your meter set to resistance or continuity test, try measuring across each pushbutton switch while pressing the pushbutton. It's a switch that's normally open and when you press the button, it completes the circuit. So, you should see infinite resistance initially and when you press the button, you should see close to 0 ohms. Check all the buttons this way.

Last edited by jetadm123; 01-02-2011 at 10:55 AM..
jetadm123 is offline   Reply With Quote
Old 01-02-2011, 04:55 PM   #24
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Okay, I tested the all the pushbuttons and they are working correctly. I tested all of them by placing my probes on the two terminals (They have 4, but it seems only 2 of them are connected) and when I push the button, the resistance is 0 ohm. I also tested the connection from the power button to the logic board, by placing the black probe on the solder joint to the negative/ground wire in the connector on the logic board, and my red probe on the solder joint which is connected to the correct wire in the connector on the logic board. And this test also passed. Whenever I pressed the power button, I got 0 resistance.

Maybe I should check if there's any voltage going to the power button?
reneg is offline   Reply With Quote
Old 01-02-2011, 05:24 PM   #25
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
Maybe I should check if there's any voltage going to the power button?

Yes, I agree with you. Please check for voltage going to the power button. If you see none then we'll have to figure where that voltage got cut off. Also, do a quick scan of the logic board to see if there are any fuses (probably marked FXX, where XX is a number).
jetadm123 is offline   Reply With Quote
Old 01-03-2011, 11:20 AM   #26
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

All the buttons get 3.11V, measured right on the solder joints next to each individual button.

I did a pretty thorough scan through the logic board but found zero fuses.

I was wondering if my problem could be caused by bad ground connection? Two of the holes to the groundscrews looks a bit wrecked. I've attached photos of the holes.
Attached Images
File Type: jpg 005_s.JPG (62.4 KB, 29 views)
File Type: jpg 006_s.JPG (73.3 KB, 23 views)
File Type: jpg 007_s.JPG (92.2 KB, 26 views)
File Type: jpg 008_s.JPG (103.8 KB, 19 views)
reneg is offline   Reply With Quote
Old 01-03-2011, 12:31 PM   #27
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
All the buttons get 3.11V, measured right on the solder joints next to each individual button.

I did a pretty thorough scan through the logic board but found zero fuses.

I was wondering if my problem could be caused by bad ground connection? Two of the holes to the groundscrews looks a bit wrecked. I've attached photos of the holes.

The ground pads seem ok. On the logic board, you have a connector that connects the ribbon cable to the pushbutton board. To the left of that connector, there are several surface mount caps and resistors. Try checking these for shorts.
jetadm123 is offline   Reply With Quote
Old 01-03-2011, 04:44 PM   #28
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

I really appreciate you taking the time to help me with this. Thank you so much for your patience!

However, I might need a little more guidance. When you say surface mount caps and resistors, do you mean these I circled? Or by caps, do you mean the bigger ones more to the left? And should I just measure resistance in the capacitators and expect it to be larger than 0 for it to be OK?
Attached Images
File Type: jpg Skærm 013_s.JPG (250.6 KB, 37 views)

Last edited by reneg; 01-03-2011 at 04:48 PM..
reneg is offline   Reply With Quote
Old 01-03-2011, 05:34 PM   #29
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
I really appreciate you taking the time to help me with this. Thank you so much for your patience!

However, I might need a little more guidance. When you say surface mount caps and resistors, do you mean these I circled? Or by caps, do you mean the bigger ones more to the left? And should I just measure resistance in the capacitators and expect it to be larger than 0 for it to be OK?
Yes, what you circled is what I was referring to. It's a quick check to look for shorts. Measure and report findings.
jetadm123 is offline   Reply With Quote
Old 01-04-2011, 08:33 AM   #30
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Okay, I'll do that tonight. However, I'm sure someone once told me it was risky to measure resistance on a PCB, as there was a possibility of damaging some of the components. Is that incorrect?
reneg is offline   Reply With Quote
Old 01-04-2011, 09:21 AM   #31
Th3_uN1Qu3
Believe in
 
Join Date: Jul 2010
City & State: Bucharest
My Country: Romania
Line Voltage: 230VAC 50Hz
I'm a: Professional Tech
Posts: 5,359
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
I'm sure someone once told me it was risky to measure resistance on a PCB, as there was a possibility of damaging some of the components. Is that incorrect?
That was applicable many years ago when ICs were extremely sensitive and meters used higher voltages. Not an issue nowadays.
__________________
Quote:
Originally Posted by PeteS in CA View Post
Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
A working TV? How boring!
Th3_uN1Qu3 is offline   Reply With Quote
Old 01-04-2011, 12:26 PM   #32
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Okay, I've attached my measurements. It was not easy to measure. I had to do some scraping on the solder joints on each side to even get a reading. Here are some comments to the results:

C33: I could not get any connection on this one. Even on 2.000M ohm, and scraping and scraping, trying different places on it and so on. Nothing. Absolutely nothing.

C34: This gave me a reading first, but when I double checked and triple checked, I could not get a connection no matter how hard I tried.

I made about 4 passes to make sure the results were reliable.
Attached Images
File Type: jpg 003_s.JPG (206.0 KB, 52 views)
reneg is offline   Reply With Quote
Old 01-04-2011, 01:40 PM   #33
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
Okay, I've attached my measurements. It was not easy to measure. I had to do some scraping on the solder joints on each side to even get a reading. Here are some comments to the results:

C33: I could not get any connection on this one. Even on 2.000M ohm, and scraping and scraping, trying different places on it and so on. Nothing. Absolutely nothing.

C34: This gave me a reading first, but when I double checked and triple checked, I could not get a connection no matter how hard I tried.

I made about 4 passes to make sure the results were reliable.

Interesting.....Now, how about checking C33 and C34 to see which pins they're connected to on the ribbon cable? Again, using the resistance or continuity setting on your meter, try to follow the path from C33 and C34 to see which switch they're connected to on the pushbutton board.
jetadm123 is offline   Reply With Quote
Old 01-04-2011, 03:50 PM   #34
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Okay, C33 is connected to pin 3 starting from the bottom, which is connected to the orange LED (Standby LED). C34 is connected to pin 2, which in turn is connected to the green LED (On LED).

Do you think the logic board shuts down because the LEDs don't work?
Actually when testing, it seems the orange LED itself works OK. It's okay bright when I'm testing resistance. But the green LED hardly lights up. However, I guess other factors might be in play here.
reneg is offline   Reply With Quote
Old 01-04-2011, 04:10 PM   #35
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

I did some more testing and found out that R95 is connected to pin 8, which is connected to the power button. And after R95 comes C32.
reneg is offline   Reply With Quote
Old 01-04-2011, 08:39 PM   #36
jetadm123
Badcaps Veteran
 
Join Date: Feb 2010
City & State: California
Posts: 2,132
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by reneg View Post
Okay, C33 is connected to pin 3 starting from the bottom, which is connected to the orange LED (Standby LED). C34 is connected to pin 2, which in turn is connected to the green LED (On LED).

Do you think the logic board shuts down because the LEDs don't work?
Actually when testing, it seems the orange LED itself works OK. It's okay bright when I'm testing resistance. But the green LED hardly lights up. However, I guess other factors might be in play here.
I don't think the logic board board is shutting down, since the voltage regulator for it is getting the required 5V. The LED is for visual purposes only and should not play a role in the power board starting up, although from your measurements, it looks like C34 is open, which adds to the confusion. But on the other hand, I'm not sure why the LEDs are are connected to the caps C33 and C34. Usually, they are connected only to a current limiting resistor.

You can try measuring the voltage on the left side of R95 when you press the power button to see if anything is happening.

Also, see if there are resistors tied to the the two LEDs (and there should be) and measure the voltage at the resistor to see if a signal (voltage) is trying to reach the LEDs when you press the power button.
jetadm123 is offline   Reply With Quote
Old 01-04-2011, 11:42 PM   #37
Ken256
New Member
 
Join Date: Oct 2009
Posts: 17
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

I just saw this thread and recognized the Samsung panel LTM240M2. If I remember, this is the same panel in my Dell 2405fpw. I did do a repair on it last summer. Some of it looks similar, but the circuit boards in my Dell are made by BenQ, and were more complex. My dell was having power-on issues, but the backlight would work briefly.

I found that the failure was caused by a surface mount capacitor inside the Samsung panel. These small ceramic capacitors are used to filter the power supply and tend to develop cracks over time. Which becomes a short directly across the power supply. This might or might not blow a fuse.

The shorted capacitor in my monitor was located inside the Samsung panel, under the metal shielding, on the column driver circuit board. I don't think you have disassembled your Sun monitor to that point, yet. There might be more diagnosing you can do on the power, inverter or logic boards before you go that far.

One easy thing you can try is to measure the resistance between the +5v and ground going INTO the panel. This is the bundle of twisted pair wires. Unplug the bundle from the video input board, but leave it connected to the panel. From the data sheet you posted, ground is pins 7, 14, 17, 24. +5 volts is pins 27-30.

Measuring resistance on the panel's supply inputs *might* tell you if there is a short inside the panel. But that's not the whole picture. There could still be a short if you get a high resistance between +5 and ground. The cable connects to a T-CON board inside the panel. The T-CON board does more video processing and buffering, and has more voltage regulators and converters. The short could be hidden by a voltage converter or a blown fuse.

Its getting late here. But I can give more info and pictures if you need to dig into it.
Ken256 is offline   Reply With Quote
Old 01-06-2011, 05:43 PM   #38
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by jetadm123 View Post
I don't think the logic board board is shutting down, since the voltage regulator for it is getting the required 5V. The LED is for visual purposes only and should not play a role in the power board starting up, although from your measurements, it looks like C34 is open, which adds to the confusion. But on the other hand, I'm not sure why the LEDs are are connected to the caps C33 and C34. Usually, they are connected only to a current limiting resistor.

You can try measuring the voltage on the left side of R95 when you press the power button to see if anything is happening.

Also, see if there are resistors tied to the the two LEDs (and there should be) and measure the voltage at the resistor to see if a signal (voltage) is trying to reach the LEDs when you press the power button.
I measured on the right side of R95 and it had 3.11V constant. When I pressed the power button, the voltage decreased to 0V. On the left side of R95 it decreased to 0.55V.
I measured on the right side of C32, but there was 0V. And when I pressed the power button, still 0V.

I also tried measuring on the different components that are attached to the LEDs, but nothing happens when I press the power button. However, when I measure voltage inside the purple rectangle, sometimes the voltage is ~0.3V, but it immediately falls to zero linearly. I have to wait a bit before I can get the same result. Does that say anything?

I tracked the different pins and what components they were connected to, and measured the different places. You can see my findings in my attachment. I hope this tells you something heh. When I look at it, it seems wrong that there's no voltage on the right side of C30, C31, C32 or C33. But what do I know? :-)
Attached Images
File Type: jpg 001 - Copy_s.JPG (309.7 KB, 36 views)
reneg is offline   Reply With Quote
Old 01-06-2011, 05:47 PM   #39
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

Quote:
Originally Posted by Ken256 View Post
I just saw this thread and recognized the Samsung panel LTM240M2. If I remember, this is the same panel in my Dell 2405fpw. I did do a repair on it last summer. Some of it looks similar, but the circuit boards in my Dell are made by BenQ, and were more complex. My dell was having power-on issues, but the backlight would work briefly.

I found that the failure was caused by a surface mount capacitor inside the Samsung panel. These small ceramic capacitors are used to filter the power supply and tend to develop cracks over time. Which becomes a short directly across the power supply. This might or might not blow a fuse.

The shorted capacitor in my monitor was located inside the Samsung panel, under the metal shielding, on the column driver circuit board. I don't think you have disassembled your Sun monitor to that point, yet. There might be more diagnosing you can do on the power, inverter or logic boards before you go that far.

One easy thing you can try is to measure the resistance between the +5v and ground going INTO the panel. This is the bundle of twisted pair wires. Unplug the bundle from the video input board, but leave it connected to the panel. From the data sheet you posted, ground is pins 7, 14, 17, 24. +5 volts is pins 27-30.

Measuring resistance on the panel's supply inputs *might* tell you if there is a short inside the panel. But that's not the whole picture. There could still be a short if you get a high resistance between +5 and ground. The cable connects to a T-CON board inside the panel. The T-CON board does more video processing and buffering, and has more voltage regulators and converters. The short could be hidden by a voltage converter or a blown fuse.

Its getting late here. But I can give more info and pictures if you need to dig into it.
Thanks for tuning in! :-) I'll keep these things in mind, but right now it seems the problem lies with the logic board, as there is no signal going out to the power supply board to start the CCFLs. But it's good to know what else to look for if we find out the logic board is fine. Thanks. :-)
reneg is offline   Reply With Quote
Old 01-08-2011, 04:55 AM   #40
reneg
Member
 
Join Date: Dec 2010
Posts: 23
Default Re: Sun 24.1" LCD monitor (Samsung LTM240M2 L02 panel)

* bump *

Is anyone able to get any meaning out of the measurements I've made? Does it tell you anything?
reneg is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums © 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 06:48 PM.
Did you find this forum helpful?