Samsung 2493HM issue

[retiredcaps]

Re: Samsung 2493HM issue

Leave the power boad face down. Unscrew the logic card and turn it face up (leave screws out). Put a piece of cardboard underneath the logic board so it is not touching the metal shield.

Leave the connections in place.

Now measure the voltage regulators on the logic card. You can still use a screw hole (GND) for the black probe.

[werthles]

Re: Samsung 2493HM issue

Ok, i replaced the two fuses on the power board and i am back where i started. Meaning, i get a solid blue led and no picture. Im posting two pics of the opposite sides of the semi-assembled boards. The metal shielding is blocking access to the pins on those chips that i need to test. Is there a possibility of not connecting some of the components to do the test or will that yield inconclusive results?

[werthles]

Re: Samsung 2493HM issue

Yeah, i figured out what kind they were. I checked the bridge rectifier and its good. I should have the fuses in a week or so. Ill post pics of my setup for testing out those chips when i get the fuses.

[retiredcaps]

Re: Samsung 2493HM issue

Now i just need to find out what kind of fuse they are.

It is hard to tell from the angle of the pictures, but they (the fuse values) are usually written write on the board.

[werthles]

Re: Samsung 2493HM issue

Now i just need to find out what kind of fuse they are.

[retiredcaps]

Re: Samsung 2493HM issue

Yeah, im getting no reading on either of the fuses. I tried all ranges of ohms.

If you mean "1" on the left hand side of the multimeter, then both of your fuses are blown. Don't confuse "1" on the left hand side of this display with 1.0 on the right hand side. The first means out of range and the second means 1.0 unit of your measurement.

You obviously want to order replacements (maybe 4 or 5 in case it blows again), but you also want to check out the bridge rectifier as well before installing the new fuses.

[werthles]

Re: Samsung 2493HM issue

Yeah, im getting no reading on either of the fuses. I tried all ranges of ohms.

[retiredcaps]

Re: Samsung 2493HM issue

As i am quite new to this,

I should explain the troubleshooting process here.

When the LED is green/blue, but you don't see the computer wallpaper with a flashlight, this implies that something is wrong with the logic board. That is why we are checking the voltage regulators on the logic board.

If the LED is green/blue and you can see an image with the flashlight, that implies something wrong with the inverter board or ccfl.

If you have no LED, that implies that there is something wrong with the power supply and/or the logic card.

[retiredcaps]

Re: Samsung 2493HM issue

It would also help if you could give us an overall picture of the boards when everything is assembled so we can see how you are testing it using a multimeter. That way, we can suggest test points that are easy to reach for the multimeter probes.

[retiredcaps]

Re: Samsung 2493HM issue

I had to set it up where the logic board and power board were hovering over each other.

Now, fully assembled, the led wont even light up. Is it completely dead?

I usually use cardboard to separate the boards if needed.

If you have no LED at all, you probably shorted something out. I wouldn't say it is completely dead, but we will now have to troubleshoot what components are shorted out or blown.

With power off and the lcd unplugged, check the following.

1) Check the two fuses by the AC input. A good use should measure less than 1.0 ohms.

2) There is a bridge rectifier (long black) just below the 2J 474J white capacitor. Number the pins 1, 2, 3, and 4. Set your multimeter on 200 ohms. Measure 1-2, 1-3, 1-4, 2-3, 2-4, and 3-4. Any reading under 30 ohms suggests it may be shorted.

[werthles]

Re: Samsung 2493HM issue

Well, in trying to test the voltage regulator i got some good sparks flying. Unfortunately how they built this thing it was impossible to fully assemble without the back panel and test the leads. I had to set it up where the logic board and power board were hovering over each other. Needless to say, as soon as i hooked it up i got shocked and i saw some sparks when i was trying to disconnect it. Now, fully assembled, the led wont even light up. Is it completely dead?

[werthles]

Re: Samsung 2493HM issue

Red circled chip: 6P741
Yellow circled chip: (brand: ST) LF25GKDK7747

[retiredcaps]

Re: Samsung 2493HM issue

As i am quite new to this, im not sure how to check the voltage regulator on the logic board.

1) What is the part number for the red circled component?

2) What is the part number for the yellow circled component?

3) To measure the DC voltage of a voltage regulator, put your multimeter on 20V DC. Plug in all boards and plug in the lcd into the AC outlet.

Put your black probe on a ground screw on the logic board. Put your red probe on each of the individual pins of the circled components. List the DC voltage for each component and pins.

[werthles]

Re: Samsung 2493HM issue

I did the flashlight check on the monitor and i did not see anything. As i am quite new to this, im not sure how to check the voltage regulator on the logic board. Any help with that would be appreciated.

[retiredcaps]

Re: Samsung 2493HM issue

If i were to replace all the caps, what brand would be preferred/suggested?

1) For the power board, we need a top down view of the board.

2) Still waiting for answers to questions #3 and #4 in post #2.

3) Forum members here like Panasonic FR, FM, and FC (in that order). Other good quality caps are listed in the FAQ section at

https://www.badcaps.net/forum/showthread.php?t=2280

Badcaps.net sells Rubycon.

4) You must use low ESR caps for a SMPS application.

[werthles]

Re: Samsung 2493HM issue

If i were to replace all the caps, what brand would be preferred/suggested? Thanks in advance.

[werthles]

Re: Samsung 2493HM issue

Here are some closeups of both boards.

[werthles]

Re: Samsung 2493HM issue

Ok, ill take some photos of it once my camera charges up. Ill probably just order some caps and replace the majorit of them.

[retiredcaps]

Re: Samsung 2493HM issue

I just stripped a capacitor off of another motherboard.

That used cap could be dry and also bad as well.

[jetadm123]

Re: Samsung 2493HM issue

This would be a good time to post some good focused photos of the top and bottom of your power board. Photos of the logic and inverter boards would also be good.