Gateway 24" LCD Model LP2407

[USchabon]

Re: Gateway 24" LCD Model LP2407

No, the menu buttons are on the bezel. The screen didn't light up at all. I can tell when the backlight is on on this monitor, and it is not on at all. The backlight is not turning on for sure. Don't know if it is because it is dead or because something isn't telling it to turn on, but it is not coming on, with or without signal. Even without signal this monitor would display the logo for a few seconds, and the menu buttons would open the GUI menu which appears on the screen, and neither show up.

[momaka]

Re: Gateway 24" LCD Model LP2407

I "fixed" the cable with a lot of silicone applied in batches, little by little adding all the cables and making sure they weren't going anywhere. I plugged it in and applied a little more silicone to the cable since this will be is resting position. Once it dried up a bit I tested for continuity and I got a solid beep on each cable, between the connector on the power supply and the male connector that is soldered into the LCD inverter.

Sounds more than good enough for testing.

Everything checked out so I went for it and tested with the component out of the TV receiver...

...the menu lights up, but the screen stays full black all the time, through power up and no matter what I do.

What gives now?
...
Could it be that all along it was the backlight that died?

Do you mean that you can see the monitor's menu/OSD controls on the screen? Can you see it well lit? (As if you would on a normally working monitor too?)
If YES, then this is not a backlight issue.

Another way to see if the backlight is working is to go in a dark room and turn on the monitor with a signal. If the monitor LED indicates that the screen is ON, then you should see the backlights in the screen turn ON as well. Even with a black image signal, you can still tell when the backlights are ON, because you should be able to see them "bleed" through the screen.
(If you are not sure what I mean, try putting a black image on a working monitor. Again, do this while in a dark room. Even though the screen is displaying all black, you will see a backlight and/or slight glow from the screen - this is the backlight.)

Feel free to post pictures of what you see as well.

[USchabon]

Re: Gateway 24" LCD Model LP2407

9 PC LCD Monitor
6 LCD Flat Screen TV
20 Desk Top Switching Power Supply
10 Desk Top Power Supply
10 Battery Charger Switching Power Supply for Power Tool
1 Battery Charger Power Tool Power Supply
6 18v Lithium Battery Power Boards for Tool Battery Packs
1 XBox 360 Switching Power Supply and M Board
6 Servo Drives 220/460 3 Phase
1 De-soldering Station Switching Power Supply 1 Power Supply
1 Dell Mother Board
10 Computer Power Supply
1 HP Printer Supply & Control Board


These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

1 Over Head Crane Current Sensing Board
2 Hem Saw Computer Stack Board

All of these had [bad] CAPs POOF
All of the mosfet that are taken out by bad caps [also bad ones]

Could it be a bad mosfet or two that need to be replaced somewhere? I guess we confirmed the power supply is ok with all the readings we gathered, so not there...

But are power supplies the only place where there are mosfets?

[USchabon]

Re: Gateway 24" LCD Model LP2407

If I power up the monitor without a signal, allowing it to boot up and go to sleep as it normally would without any signal being fed, THEN I plug the TV signal in... based on the menu buttons lighting up I can confirm that it does in fact detect the signal.

This points away from the ROM needing to be flashed with the software again. Instead it points towards the backlight, or something else having to do with the LCD inverter, but not the logic board...

[USchabon]

Re: Gateway 24" LCD Model LP2407

The one that broke is the one going to the LCD Inverter, which has 8 cables.

I haven't received the new adjustable one yet, and I was hoping to fix this quickly so I got impatient and went for it. Things went a lot easier than the first time, so I think a lot of it was just inexperience. I think the only reason why things took a while this second time around was just not knowing enough to interpret the readings I was getting.

I "fixed" the cable with a lot of silicone applied in batches, little by little adding all the cables and making sure they weren't going anywhere. I plugged it in and applied a little more silicone to the cable since this will be is resting position. Once it dried up a bit I tested for continuity and I got a solid beep on each cable, between the connector on the power supply and the male connector that is soldered into the LCD inverter.

Everything checked out so I went for it and tested with the component out of the TV receiver...

...the menu lights up, but the screen stays full black all the time, through power up and no matter what I do.

What gives now?

We've replaced all caps on Logic board, all caps (but the big one) on the power control, and both caps on the LCD inverter. The cable that cracked looks to be OK.

Could it need to be flashed? Maybe the software got wiped?

Could it be that all along it was the backlight that died?

[momaka]

Re: Gateway 24" LCD Model LP2407

Nevermind, I think they are all fine, some of them just beep for about a second or so before shutting up

Like I said, that's other caps in the circuit charging up, so don't worry about it if beeps quickly and stops.

That's why I usually suggest to check with the 200 Ohm scale, and not anything else. Continuity is a very general setting - typically used for simple stuff, like seeing if a long wire has breaks in it. Continuity is NOT good for determining if stuff is shorted or not. Most multimeters will show continuity and beep only if resistance is less that 25-100 Ohms... which again, is NOT a good indicator for short circuit.

Question, the little 10uF 16V however gives me an infinity reading (1 on the left). Is that normal.

Yes.

In theory, capacitors have infinite resistance. But some caps can become (electrically) leaky, so you may actually see a high resistance across their leads. This is all out-of-circuit measurements, of course. In circuit, it can be a completely different story, depending on what is connected to that capacitor.

Does this look like the right one? Not like I am going to see it anyway

http://www.ebay.com/itm/5-Pcs-2-54mm...AAAOSw7hRWPFUv

Looks okay to me. But it is an 8-pin connector, whereas yours looks like a 9-pin. Or am I mistaken here?

Gosh, should I be worried about these little soldering points?

How does it work when it comes to "safe areas" for people that use 3 lbs of solder like me?

Just use less solder and more flux to re-do the joint until it looks right.

I'm wondering, though... are you using your new adjustable iron or the "old" 30 Watt one?

[USchabon]

Re: Gateway 24" LCD Model LP2407

Awesome. Thanks Budm!

Does this look like the right one? Not like I am going to see it anyway

http://www.ebay.com/itm/5-Pcs-2-54mm...AAAOSw7hRWPFUv

[budm]

Re: Gateway 24" LCD Model LP2407

It looks like JST connector:
http://www.ebay.com/sch/i.html?_from...n+jst&_sacat=0

[USchabon]

Re: Gateway 24" LCD Model LP2407

Nevermind, I think they are all fine, some of them just beep for about a second or so before shutting up

"I was using 2000k to test them" Then it is not shorted then, you need to use 200 Ohms scale.

Cool, makes sense.

Question, the little 10uF 16V however gives me an infinity reading (1 on the left). Is that normal.

Assuming it is, I am ready to rest but I would much rather order the cable than short the whole thing out again. Where can I get this:

[budm]

Re: Gateway 24" LCD Model LP2407

"I was using 2000k to test them" Then it is not shorted then, you need to use 200 Ohms scale.

[USchabon]

Re: Gateway 24" LCD Model LP2407

I was using 2000k to test them

Budm, do you have any tricks to cleaning up the PCB? I am getting connectivity between two of those points even without any solder (that I can see) and without a cap installed...

[budm]

Re: Gateway 24" LCD Model LP2407

BTW, 001 Ohms, or 001K Ohms?
I doubt that the cap shorted out.

[USchabon]

Re: Gateway 24" LCD Model LP2407

%#$@!! Now I have the same issue with another one of those small tight cap holes... is there a trick that helps to clean up the PCB so that I stop getting connectivity between the holes even without a cap installed?

[USchabon]

Re: Gateway 24" LCD Model LP2407

Pheeew, I think I got it, please disregard the last post, working on the rest now.

[USchabon]

Re: Gateway 24" LCD Model LP2407

Ugh... I am getting a solid tone from the multi when testing for continuity between these two points. I used the vacum pen a million times and I still can't seem to get rid of whatever is connecting the two points, with or without the cap. I tested the cap and it seems to be ok, but the beep is there even when I test like this (photos):

[USchabon]

Re: Gateway 24" LCD Model LP2407

Okay, sorry, but you got me confused again. First you say dropped down to "001", then to "1". Again, be specific. If it's a "1" on the left side of your multimeter screen with no other digits behind it, then that is an "out of range" indicator. When you get that, just say "I get out of range reading". That way, we (err. I? ) don't confused about what you are seeing.

Hahaha, sorry, yes, both times I meant "001"

Yes sir.

Gosh, should I be worried about these little soldering points?

How does it work when it comes to "safe areas" for people that use 3 lbs of solder like me?

Seems so right now.
That said, were you able to (temporarily) fix the cable between the power and inverter boards?

No, let's order it... I am concerned about blowing the whole thing up again

[momaka]

Re: Gateway 24" LCD Model LP2407

I get a continuous beep between the negative on both caps and 3 of the power connectors

Good. So the negative leads are connected well then..

I get a SUPER short beep, not even half a second, between the positives on both caps and the same 3 power connectors.

Good.
That means the positive leads on the cap are also making contact. If you had a long beep / good continuity to the same 3 pins as the negative leads, then I would have been worried, since that would indicate a short-circuit between the 24V rail and ground. But since that is not the case, were are okay here.

Yup. Thank you for helping me out. To be safe I just checked them again. They both started somewhere around 300 or 200, then dropped to "001". Then I used a screw driver to discharge them and tested them again, they started with a small negative value them went up gradually and dropped again to 1.

Okay, sorry, but you got me confused again. First you say dropped down to "001", then to "1". Again, be specific. If it's a "1" on the left side of your multimeter screen with no other digits behind it, then that is an "out of range" indicator. When you get that, just say "I get out of range reading". That way, we (err. I? ) don't confused about what you are seeing.

So, does it look like we are on to swapping the caps on the logic board?

Yes sir.

It seems everything else might be ok, right?

Seems so right now.
That said, were you able to (temporarily) fix the cable between the power and inverter boards?

[USchabon]

Re: Gateway 24" LCD Model LP2407

First test for continuity between the negative lead of each capacitor and the pins on the power connector. At least a few pins should show a low resistance and/or multimeter beeping at you for several seconds (a quick beep does not mean good continuity). If YES, then the negative lead on the capacitor is connected.

I get a continuous beep between the negative on both caps and 3 of the power connectors.

Next, repeat the same procedure, but on the positive lead of each cap. Again, your multimeter should beep or show a low resistance for more than a few seconds to some of the pins on the power connector.

I get a SUPER short beep, not even half a second, between the positives on both caps and the same 3 power connectors.

[QUOTE=momaka;668471]But note: you should NOT get continuity / low resistance / beeping between the capacitor's positive and negative leads - at least not when you keep the multimeter probes connected for several seconds. (Again, a short beep is OK - usually means a capacitor somewhere charging. But a loooong beep typically indicates good continuity.)[quote]

I get no sound at all when connecting the positive and negative connectors. Same for both of the capacitors.

No.

Good stuff! I was dreading having to wait for a shipment of 2 caps hehehe

When you say "went down to 1", is that the leftmost digit "1" on the multimeter screen or is it something like "1.0" or "1.00" or similar?

Yup. Thank you for helping me out. To be safe I just checked them again. They both started somewhere around 300 or 200, then dropped to "001". Then I used a screw driver to discharge them and tested them again, they started with a small negative value them went up gradually and dropped again to 1.

So, does it look like we are on to swapping the caps on the logic board? It seems everything else might be ok, right?

[momaka]

Re: Gateway 24" LCD Model LP2407

I only get a short beep sometimes, usually when I first touch it, but it is very short and I have a very hard time reproducing it.

That's typical when "testing" caps with your multimeter. Basically, it is the capacitor charging up from the multimeter. Because the capacitor is initially discharged, it will draw more current from the multimeter, and the multimeter will see a low resistance and/or beep at you... but this only happens for a short moment or two, because the capacitor quickly charges up and stops drawing current. Then the multimeter sees that as a high resistance.

I thought that the problem might be that the positive sides of the caps didn't have any solder at all on the top side, only on the bottom... so I quickly added some solder to the top side, but after re-testing I still get the same... no beep between either cap when I try continuity between their positive leads and the power connector.

First test for continuity between the negative lead of each capacitor and the pins on the power connector. At least a few pins should show a low resistance and/or multimeter beeping at you for several seconds (a quick beep does not mean good continuity). If YES, then the negative lead on the capacitor is connected. Next, repeat the same procedure, but on the positive lead of each cap. Again, your multimeter should beep or show a low resistance for more than a few seconds to some of the pins on the power connector. But note: you should NOT get continuity / low resistance / beeping between the capacitor's positive and negative leads - at least not when you keep the multimeter probes connected for several seconds. (Again, a short beep is OK - usually means a capacitor somewhere charging. But a loooong beep typically indicates good continuity.)

Maybe I did kill the caps when that sucker sparked like there was no tomorrow..?

No.

How can I test the cap itself? I looked that up and found I needed to set the multi to Ohms (2000k), and hook it up to both leads... I got about a 600-and-something reading and it quickly went down until it reached 1.

I tested both several times and I get what seems to be kind of random values that almost always go down to 1 in a matter of a second or two. Sometimes it starts around 400, sometimes 1200, I even saw -120 or so. Almost always it drops down to 1 within a second or two, but sometimes it stops at 2.

When you say "went down to 1", is that the leftmost digit "1" on the multimeter screen or is it something like "1.0" or "1.00" or similar?

The reason I ask is because I want to make sure you are not confused about reading your multimeter.

For manual-ranging multimeters, a digit "1" on the leftmost side of the screen typically means out of range value - i.e. the value you are trying to measure (whether it is resistance, or current, or voltage) is too high for the scale you have selected and you need to go to the next higher scale.
On the other hand, a number, such as "1.0" or "1.00" or "10.0" or "100" or "1000" is different from the "1" digit described above - these numbers represent an actual reading.

As for auto-ranging multimeters, you typically get a "OL" on the screen if the value you are trying to measure is too high for the multimeter.

[USchabon]

Re: Gateway 24" LCD Model LP2407

Ok, so I thought I tested the caps on the inverter board properly using the multimeter, I remember getting a beep...

I just tested them again and I only seem to get a beep on the leads that look the worst (the ones where I had to use a ton of solder). These are the negative leads.

I only get a short beep sometimes, usually when I first touch it, but it is very short and I have a very hard time reproducing it.

I thought that the problem might be that the positive sides of the caps didn't have any solder at all on the top side, only on the bottom... so I quickly added some solder to the top side, but after re-testing I still get the same... no beep between either cap when I try continuity between their positive leads and the power connector.

Maybe I did kill the caps when that sucker sparked like there was no tomorrow..? How can I test the cap itself? I looked that up and found I needed to set the multi to Ohms (2000k), and hook it up to both leads... I got about a 600-and-something reading and it quickly went down until it reached 1.

I tested both several times and I get what seems to be kind of random values that almost always go down to 1 in a matter of a second or two. Sometimes it starts around 400, sometimes 1200, I even saw -120 or so. Almost always it drops down to 1 within a second or two, but sometimes it stops at 2.

I tried a new and un-used 1000uF 25V cap and I get a very low value that slowly climbs higher and higher over time.

BTW, the caps in question are still on the board.