SyncMaster 2493HM with no picture and solid blue LED

[InfiniteSquareWell]

My problem is related to this thread, but it's over a year old, and my problem is slightly different.

I have the same type of monitor (Samsung SyncMaster 2493HM) with the same basic problem: When I turn it on, I get no picture, but the LED remains a solid blue, which is supposed to mean that the logic board and power supply are working. I, however, don't hear a persistent clicking sound; I only hear one quick "click" when I touch the power button.

I received the monitor as a gift from a friend who knew I liked to repair electronics. When I first attempted to repair it about a month ago, I heard something come loose inside the case as I was about to open it. Rather than continuing to pry the monitor apart, I decided to plug it back in, and it worked! It continued to work without any issues until I went on vacation last week.

I was gone for about a week and a half, and the monitor was left sitting in my apartment (without air conditioning in Florida). Upon attempting to use it again, I have found that it is having the same exact problem it had when I first received it. I have now actually opened it only to find that all of the capacitors appear to be fine (no bulging whatsoever).

One thing I was expecting to find once I opened it was whatever had come loose originally; I found nothing. I removed the logic board and found that some component on it rattles when I shake it. I have no idea if this is the problem since it appeared to be present when the monitor was working.

I do not think that the capacitors are the problem, and I am hesitant to replace them because my current soldering iron is awful for desoldering (it can't seem to heat any solder through the desoldering braid).

I love this monitor... is it wrong to love a monitor? When it works, it is simply beautiful. My backup monitor is from ~2004 and is ugly by comparison, but at the very least it is reliable. I very much want to fix this, so if anyone has any suggestions, they will be greatly appreciated.

[retiredcaps]

Originally Posted by InfiniteSquareWell

When I turn it on, I get no picture, but the LED remains a solid blue, which is supposed to mean that the logic board and power supply are working.

1) It could be a simple as a blown fuse or shorted transistor somewhere in the inverter section.

2) Post clear focused top down pictures of all your boards following my sig file below exactly. We want the picture compositions like so

http://www.badcaps.net/forum/showpos...94&postcount=1

3) If you have a multimeter, post a picture of it for one retiredcaps' bonus points.

[InfiniteSquareWell]

Here are the pics of the boards in my monitor and my multimeter. Let me know if any additional pictures would be helpful.

[retiredcaps]

1) One retiredcaps bonus point for a picture of your RadioShack multimeter.

2) Now use the multimeter to see if F1 is blown on the inverter board. A good fuse should measure less than 1.0 ohm. Report your findings.

3) There are 4 mosfets on the inverter board. One of them is U6 (APM4030A). I can't make out the pcb designation for the other 3. For all 4, see if they are shorted. Section 2 at

http://www.badcaps.net/forum/showpos...4&postcount=19

has procedures on how to test.

Report your findings for all 4. You should have 12 readings in total.

4) The power board has a lot of brown dried up glue that might have turned conductive. I suggest removing them with an exacto knife or like too.

[InfiniteSquareWell]

Originally Posted by retiredcaps

2) Now use the multimeter to see if F1 is blown on the inverter board. A good fuse should measure less than 1.0 ohm. Report your findings.

3) There are 4 mosfets on the inverter board. One of them is U6 (APM4030A). I can't make out the pcb designation for the other 3. For all 4, see if they are shorted. Section 2 at

http://www.badcaps.net/forum/showpos...4&postcount=19

has procedures on how to test.

Report your findings for all 4. You should have 12 readings in total.

I checked the fuse and the mosfets and all give readings which indicate they are working (fuse = 0 - 0.1 ohms, each of the 12 readings for the mosfets >= ~4700 ohms).

I'll remove the dried glue tomorrow. Any other suggestions? Thanks for your help so far.

[retiredcaps]

Originally Posted by InfiniteSquareWell

Any other suggestions?

1) On the power board, there is usually a legend by the connectors. Show a picture of it

2) We are looking for BL_ON or something like that. This pin is generated by the main/logic board and tells the power supply to turn on the backlights. What is the DC voltage on this pin?

3) What is the DC voltage on both sides of Fuse F1 (inverter board) wrt to ground?

[retiredcaps]

4) Q4 on the inverter board looks like a voltage regulator.

What is the part number? What are the DC voltages for each pin wrt to ground?

Report them like so along with the part number (include all lines on the IC) of the IC.

U100
AS1117-33
pin 1 = 0.0
pin 2 = 3.3
pin 3 = 5.0

[retiredcaps]

5) If you hookup a source displaying your favourite wallpaper, do you see it by shining a flashlight on it or in a really dark room?

6) IC304 and IC113 on the main/logic board look like voltage regulators. What are the part numbers and DC voltage of each pin with respect to ground?

Report them like so along with the part number (include all lines on the IC) of the IC.

U100
AS1117-33
pin 1 = 0.0
pin 2 = 3.3
pin 3 = 5.0

[selldoor]

Not that it is any help at the moment the rattle may be a ball switch S301?
whch moves the display landscape/portrait - not listed as something this screen has but perhaps the board is used in other sets - I suppose it could also be vesa mounted.

[selldoor]

I see retired caps has suggested the flashlight on screen but reading through
I cant see if you have been asked if the screen flashes on at all when you
switch on - try in a dimly lit room.

[InfiniteSquareWell]

The monitor seems to be working again, although I didn't really do anything. While I was measuring the 5V feed to the logic board, I heard a slight click and the backlight came on. I put the monitor back together, and now it's working again.

Thanks a lot for the help! It's hard to find anyone with enough technical experience to diagnose a faulty monitor. I'll definitely be back if the monitor fails again.

[tom66]

Sounds like a cold solder joint - let us know WHEN it fails (not IF.)

[InfiniteSquareWell]

Originally Posted by tom66

Sounds like a cold solder joint - let us know WHEN it fails (not IF.)

Yeah... so I got up this morning, and it's not working again. Once it started working last night, I didn't have any problems with it. I'm starting to think I should never turn it off for more than 5 minutes.

So this is typical of a cold solder joint? How would I locate that?

[selldoor]

Pictures are not really clear enough for troubleshooting- set it all up as it was when you
were testing the 5v in and flex the board where you were probing. If it comes on take a close up in focus shot of the area front and back. If it doesnt come on (again with it all set up to come on) get a hair dryer and apply gentle heat - start with the area you were probing and work around the whole board then if still nothing move onto the power supply board.

[InfiniteSquareWell]

I think the problem might be with the power supply. I measured the voltages delivered to the inverter and logic boards (on the power board side) and found that the 5V output to the logic board is ~0.5V, and the 24V output to the inverter board is ~100mV. I checked with two multimeters and concluded the same thing. The power switch enable line (the blue wire on the smaller connection to the logic board) was ~3.5V, however.

Could the problem still be a capacitor or is a cold solder joint more likely? None of the solder joints are visibly loose, but I don't have a good eye for that.

[selldoor]

Could be either may have just come on when caps got heated up hair drier will also boost the caps specs slightly so still try that.

[Duncanbest]

The attached picture of DONG YANG's power supply remind me the bad glue cause the PFC NG at other Samsung LCD monitor.

Maybe aging glue is your problem.

[selldoor]

Originally Posted by Duncanbest

The attached picture of DONG YANG's power supply remind me the bad glue cause the PFC NG at other Samsung LCD monitor.

Maybe aging glue is your problem.

Covered that in post 4 & 5 apparently

[InfiniteSquareWell]

I tried flexing the board in that spot and repeating everything as I did when it started working, but still nothing. I do not have a hair dryer, so I haven't tried that yet. I've included some pictures of the power supply that will hopefully be easy to see.

What I've been doing is probing around the power board to look for any active voltages at all. The voltage regulators coming from the sides of the large component in the sixth picture are not outputting anything close to what they should (0.5V or less), but there are some capacitors and other components with reasonable voltage levels (5 - 15V).

As you can see in the pictures, I haven't removed all the dried glue yet. It is very tough to remove, and I'm worried about breaking components as I do it. One of the components I removed glue from is shown in the last picture and is the yellow component located next to the capacitor. When I turn on the power supply, I hear and have seen a spark, and so maybe I breached the yellow plastic casing and made the problem worse.

So should I just continue to remove the glue? If that ends up being the solution, do I need to replace all the old glue with new glue?

[selldoor]

Originally Posted by InfiniteSquareWell

One of the components I removed glue from is shown in the last picture and is the yellow component located next to the capacitor. When I turn on the power supply, I hear and have seen a spark, and so maybe I breached the yellow plastic casing and made the problem worse.

Sounds bad It may be that you just uncovered the problem rather than caused it, either way,damage is done and those transformers seem hard to get hold of. If you can get the rest of the glue off without causing any more damage it may be repairable- we would need close up pics to inspect.
Glue does not need replacing.