Gateway 24" LCD Model LP2407

[USchabon]

Re: Gateway 24" LCD Model LP2407

I checked on these pins, and got these values (starting away from power cord and going towards it):

1. 0.04 (200 Ohms)
2. 2.65 (20k Ohms)
3. 2.65 (20k Ohms)
4. 0.05 (200 Ohms)

[USchabon]

Re: Gateway 24" LCD Model LP2407

Well, here are the best photos I could get without getting the big camera out.

All of them seem to be the same: 9985GM - 645022

The schematics read like there is 3 source pins and 4 drain pins on the other side. Does it matter which of them I measure?

[budm]

Re: Gateway 24" LCD Model LP2407

I can read P/N on one of the 4 Power MOSFETs, 9985GM.
You need to find out what the other 3 are all the same or not.
See spec sheet for the Source and the Drain pin of the 9985GM.

[USchabon]

Re: Gateway 24" LCD Model LP2407

If I check the caps at 200 Ohms I get a 1 (to the left) on both caps.

Which are the MOSFETs, and which are the source and the drain pins? I don't see anything like this on the LCD inverter board. Do you mean on the power supply unit?

[budm]

Re: Gateway 24" LCD Model LP2407

I set the multi to 20k and I get 2.63 and 2.64 on the caps. Does that mean the MOSFETs are fine because it is less than 10?

We are looking for low resistance, so use 200 Ohms RANGE, so 2.63K Ohms mean you do not have shortes between the two legs of the caps.
Right now it does not mean the MOSFETs are not shorted out until you check the resistance between the Source pin and the Drain pins of the MOSFET.

[USchabon]

Re: Gateway 24" LCD Model LP2407

I set the multi to 20k and I get 2.63 and 2.64 on the caps. Does that mean the MOSFETs are fine because it is less than 10?

[budm]

Re: Gateway 24" LCD Model LP2407

So you have blown fuse, so next thing you need to do is to check resistance between the two legs of those two filter caps to find out if it is showing >10 Ohms, if it does, then it can be solder bridge dues poor soldering works, shorted out power MOSFETs, you need to get the P/N of those MOSFETs.
If they are shown as shorted circuit, then you need to get then new inverter board because I do not believe you can do surface mounted repair.

[USchabon]

Re: Gateway 24" LCD Model LP2407

I did the same at all Ohms ranges of the multimeter and got nothing on the fuse when touching both gold ends

[USchabon]

Re: Gateway 24" LCD Model LP2407

How do I test the resistance for the fuse? If I set the multi to continuity and connect the gold sides and I get nothing

[budm]

Re: Gateway 24" LCD Model LP2407

Does it show very high resistance? If it does,then you may have done bad power MOSFETs the 8-pin SMD devices, that are shorted out. You will need to get the P/N so you can test the resistance between Source and Drain pins for low resistance readings.

[USchabon]

Re: Gateway 24" LCD Model LP2407

Fuse (White body with gold ends) designator is F1 as printed on the board right next to the inverter connector.

Cool. How can I make sure I order the right one? And can it be soldered in place?

[budm]

Re: Gateway 24" LCD Model LP2407

I'll go pick up a new 9V and post the readings again, but it was a new battery when I bought it around 1 month ago or less. Could be a bad one, could have left it on... we'll find out.

What does the inverter's fuse look like? Can it be swapped? Would make sense since the spark that jumped out of the socket when I messed up was about 3 inches long HAHAA

Fuse (White body with gold ends) designator is F1 as printed on the board right next to the inverter connector.

[USchabon]

Re: Gateway 24" LCD Model LP2407

I'll go pick up a new 9V and post the readings again, but it was a new battery when I bought it around 1 month ago or less. Could be a bad one, could have left it on... we'll find out.

What does the inverter's fuse look like? Can it be swapped? Would make sense since the spark that jumped out of the socket when I messed up was about 3 inches long HAHAA

[budm]

Re: Gateway 24" LCD Model LP2407

Your meter batteries must be low since you are getting 29.9Vdc feeding the inverter board, it should be around 24VDC.
The inverter fuse has to be bad, open circuit, because you are not getting the 24VDC on the two filter caps on the inverter board.

[USchabon]

Re: Gateway 24" LCD Model LP2407

With all the boards plugged in and the cable plugged into the wall, I set the multi to 200 VDC and this is what I get on the connector on the LCD Inverter (starting with the red cable):
1. 29.9V
2. 29.9V
3. 0V
4. 0V
5. 4.7V
6. 0V
7. 3.2V
8. 3.2V

Between the legs of the caps I replaced (multi set to 200m VDC) I get 0.02V on both. This is with all boards plugged in and cable plugged into the wall.

I then unplugged the monitor and tested those caps again. The first one started at about 130 (multi set to 200m VCD) and it slowly went down to 0, then I tested the other cap and it said 0.

[budm]

Re: Gateway 24" LCD Model LP2407

LCD INVERTER CN ON THE POWER BOARD (left to right towards LCD Inverter):
1. 0V
2. 3.28V
3. 0V
4. 5.18V
5. 0V
6. 0V
7. 25.9V
8. 25.9V

So how about at the inverter board connector?
Also what DCV do you have between the two legs of the caps you replaced on the inverter board?

[USchabon]

Re: Gateway 24" LCD Model LP2407

Even if you have one or more bad lamps, the inverter circuit should fire up the lamps then the protection circuit will monitor to see if ALL the lamps start conducting (lamps flash on) and stay conducting, but if the one or more lamps do not stay on within 3seconds then the inverter protection will shutdown the circuit.
So you at least see the lamps flash on for seconds if the inverter board is active.
So what DCV do you have now on the inverter connector? At least one pin should have the 24V, then at least two more pins should have <5VDC (one for bl-on (>2.5V), one for DIM (between 1V or so ~4.5vdc)).
DCV between the two legs of each of the two filter caps that you replaced on the inverter board? 24VDC?

I am having a hard time following your post, but please take a look at these measurements. Maybe the information you are asking me to gather is already here?

Here are the readings for the cable going to what I've been calling the LCD board (the one with the Frankenstein soldering job )

From left to right (moving up towards the LCD board):
1. 0V
2. 0V
3. 0V
4. 5.43V
5. 0V
6. 0V
7. 23.3V
8. 23.3V

Here are the readings for the cable going to what I've been calling the logic board (the one with all the processors and the I/O inputs)
1. 5.43V
2. 5.43V
3. 5.43V
4. 5.43V
5. 0V
6. 0V
7. 0V
8. 0V
9. 0V
10. 0V

Ok, I completely removed the LCD Inverter and the little USB board, I plugged in the logic board to the power board (flipped and on the back of my mouse pad) then I plugged in the power board and took all the same measurements as before:

LCD INVERTER CN ON THE POWER BOARD (left to right towards LCD Inverter):
1. 0V
2. 3.28V
3. 0V
4. 5.18V
5. 0V
6. 0V
7. 25.9V
8. 25.9V

LOGIC BOARD CN ON THE POWER BOARD (starting from the red cable)
1. 5.18V
2. 5.18V
3. 5.18V
4. 5.18V (also red)
5. 0V
6. 0V
7. 0V
8. 0V
9. 3.28V
10. 0V

[budm]

Re: Gateway 24" LCD Model LP2407

Even if you have one or more bad lamps, the inverter circuit should fire up the lamps then the protection circuit will monitor to see if ALL the lamps start conducting (lamps flash on) and stay conducting, but if the one or more lamps do not stay on within 3seconds then the inverter protection will shutdown the circuit.
So you at least see the lamps flash on for seconds if the inverter board is active.
So what DCV do you have now on the inverter connector? At least one pin should have the 24V, then at least two more pins should have <5VDC (one for bl-on (>2.5V), one for DIM (between 1V or so ~4.5vdc)).
DCV between the two legs of each of the two filter caps that you replaced on the inverter board? 24VDC?

[USchabon]

Re: Gateway 24" LCD Model LP2407

I can't seem to find one, or a used monitor for parts that can be confirmed to have a working backlight... do you guys have any links to sites that might have the part? And does it seem that it must be the backlight or am I wrong to assume that?

[USchabon]

Re: Gateway 24" LCD Model LP2407

Where/how could I get a backlight? I guess I need to open it all the way and test the backlight somehow?