LG Flatron 1718S-BN has power but no video

[De3rcr]

Hi Everyone,

This is my first time posting about a problem I have. I've fixed 2 other lcd's by replacing caps and they work fine, but this one I don't know what to do next. I have this monitor that doesn't show any video when I connect it to a computer. I replaced the power supply caps with panasonic FM's but I still get the same results.

I get 5.14v at the power supply output cable and the backlights seem to came on and stay on, but there is no video, the menu doesn't show when I push the button either.

[retiredcaps]

Re: LG Flatron 1718S-BN has power but no video

I have this monitor that doesn't show any video when I connect it to a computer.

I get 5.14v at the power supply output cable and the backlights seem to came on and stay on, but there is no video, the menu doesn't show when I push the button either.

Excellent clear focused pictures. A+

Test voltage regulators U101 and U102. It looks like U102 should be outputting 1.8V DC. I can't tell with U101 because of the angle of the photo. With U102, the last two digits are 18 which indicates 1.8V DC.

[bonney]

Re: LG Flatron 1718S-BN has power but no video

try reseating the screen cable on both screen and logic board also a good check of dry joints on logic board

[PlainBill]

Re: LG Flatron 1718S-BN has power but no video

Seriously good pictures, Dude. I have only one question. In the first picture one pants leg appears to be longer than the other. Is that a fashion thing, or just the camera angle?

This is a strange problem. Here are a few things to check.

1. Is the monitor detected when it is hooked up to a computer?

2. You have indicated the "backlights seem to came (sic) on and stay on". Could you verify that? Usually there is some light leakage from the back of the LCD panel when the backlights are on.

3. Check if the backlights are on when the cable from the power supply to the logic card is disconnected.

4. There are two voltage regulators on the logic card - U101 and U102. Pins 1 and 3 are numbered, the tab is pin 2. With the logic card connected to the power supply, power supply on, etc, measure voltage from one of the mounting screws to each pin on each voltage regulator.

5. Does the power LED react when you push the power button?

PlainBill

[De3rcr]

Re: LG Flatron 1718S-BN has power but no video

OK, got some more info
The pant leg was just the camera angle.
1. With just the power to the monitor I power it on and the light is green, when I plug in the vga cable it goes from amber to green(this is with the pc off). With it connected to the pc and power on its amber then when the pc is turned on it goes green, and when I shutdown the pc it goes back to amber.
2. The backlights are working, I took the panel out of the plactic back panel and saw that the lights were on.
3. The power button panel plugs into the logic board so I can't turn it on without the logic board pluged into the power board.
4. Voltages without the vga cable attached
U101
pin 1: 0v
pin 2: 3.31v
pin 3: 5.18v

U102
pin 1: 0v
pin 2: 3.84v
pin 3: 5.16v

It seems to act like it normally would but it doesn't show any video

Thanks for your help

[retiredcaps]

Re: LG Flatron 1718S-BN has power but no video

4. Voltages without the vga cable attached
U101
pin 1: 0v
pin 2: 3.31v
pin 3: 5.18v

U102
pin 1: 0v
pin 2: 3.84v
pin 3: 5.16v

U101 looks good. U102 pin 2 looks suspicious. If U102 is AS1117L-18, then I believe it should be 1.8V DC.

[jetadm123]

Re: LG Flatron 1718S-BN has power but no video

OK, got some more info
The pant leg was just the camera angle.
1. With just the power to the monitor I power it on and the light is green, when I plug in the vga cable it goes from amber to green(this is with the pc off). With it connected to the pc and power on its amber then when the pc is turned on it goes green, and when I shutdown the pc it goes back to amber.
2. The backlights are working, I took the panel out of the plactic back panel and saw that the lights were on.
3. The power button panel plugs into the logic board so I can't turn it on without the logic board pluged into the power board.
4. Voltages without the vga cable attached
U101
pin 1: 0v
pin 2: 3.31v
pin 3: 5.18v

U102
pin 1: 0v
pin 2: 3.84v
pin 3: 5.16v

It seems to act like it normally would but it doesn't show any video

Thanks for your help

Great pics and welcome to the forum! I suspect U101 is a 3.3V regulator and looks to be good. However, U102 seems a bit high. Please list the part numbers of U101 and U102.

[De3rcr]

Re: LG Flatron 1718S-BN has power but no video

Here they are

U101
A1
S1117L-33
B0549

U102
A1
AS1117L-18
B0548

[PlainBill]

Re: LG Flatron 1718S-BN has power but no video

Here they are

U101
A1
S1117L-33
B0549

U102
A1
AS1117L-18
B0548

Bingo!! U102 is toast. It should be 1.8 volts. No promises that you will have a working monitor if you replace it. Feeding 3.84 volts into an IC designed to take 1.8 volts tends to do BAD things.

PlainBill

[De3rcr]

Re: LG Flatron 1718S-BN has power but no video

Anybody know where I can find this part or the locic board, I've searched the parts and can't find any?

Thanks for the help finding out what was wrong with it.

[jetadm123]

Re: LG Flatron 1718S-BN has power but no video

This is a common off the shelf part made by several manufacturers. Available through digikey.com. Part # 497-7308-1-ND

Select USPS First Class Ship for lowest cost shipping.

[De3rcr]

Re: LG Flatron 1718S-BN has power but no video

This is a common off the shelf part made by several manufacturers. Available through digikey.com. Part # 497-7308-1-ND

Select USPS First Class Ship for lowest cost shipping.

Thanks jetadm123
I searched digikey with the part number off the chip and got no results(guess I was just searching wrong). will order and see if my soldering skills are good and post results.

[jetadm123]

Re: LG Flatron 1718S-BN has power but no video

Unfortunately, all the manufacturers have their own part numbers for the same part. In addition, there are several variations of this regulator:1.8V, 3.3V, etc. Therfore, it's not suprising that one has trouble finding the part.

[bonney]

Re: LG Flatron 1718S-BN has power but no video

Pin 48 is the panel enable pin 84 is the reset might be worth checking them

[johnboy183]

Re: LG Flatron 1718S-BN has power but no video

Just acquired one of these with exactly the same symptoms. Read this post and tried the two voltage regulators and the 1.8 was reading 3.84. Luckily I had another similar logic board with the same regulators so scavenged the 1.8 from it and used it to replace the faulty one and the monitor has now fully fired up and been running for several hours!
Really glad I saw this post as I was certainly scratching my head upto that point!

[PlainBill]

Re: LG Flatron 1718S-BN has power but no video

Just acquired one of these with exactly the same symptoms. Read this post and tried the two voltage regulators and the 1.8 was reading 3.84. Luckily I had another similar logic board with the same regulators so scavenged the 1.8 from it and used it to replace the faulty one and the monitor has now fully fired up and been running for several hours!
Really glad I saw this post as I was certainly scratching my head upto that point!

Good news. Glad it worked for you.

PlainBill

[shovenose]

Re: LG Flatron 1718S-BN has power but no video

hey op did u ever get it fixed?

[De3rcr]

Re: LG Flatron 1718S-BN has power but no video

I ordered the part Friday, should get it tomorrow or tuesday. Then I'm going to try to replace it. I've never replaced a part that small or a surface mounted chip, I've only replaced caps on power supply boards. Anybody have advice on how to go about it?

[jetadm123]

Re: LG Flatron 1718S-BN has power but no video

I ordered the part Friday, should get it tomorrow or tuesday. Then I'm going to try to replace it. I've never replaced a part that small or a surface mounted chip, I've only replaced caps on power supply boards. Anybody have advice on how to go about it?

You can use ChipQuik, or if you have a fine sharp pair of diagonal wire cutters, you can cut through each of the 3 legs. With your soldering iron, heat the tab and remove the chip with a pair of needle nose pliers. If you're having trouble melting the solder, try melting a small amount of lead/tin solder along the edge of the tab. Once chip is removed, with your soldering iron and a pair of pliers or tweezers remove each leg.

[De3rcr]

Re: LG Flatron 1718S-BN has power but no video

You can use ChipQuik, or if you have a fine sharp pair of diagonal wire cutters, you can cut through each of the 3 legs. With your soldering iron, heat the tab and remove the chip with a pair of needle nose pliers. If you're having trouble melting the solder, try melting a small amount of lead/tin solder along the edge of the tab. Once chip is removed, with your soldering iron and a pair of pliers or tweezers remove each leg.

Thanks jetadm123
Digikey sent an email that it shipped friday. We'll see how long it takes to get here in FL. then I will try what you suggest.