Viewsonic VG2230wm no power

[snakezz]

Greetings,

I have a LCD Monitor Viewsonic VG2230wm that doesn't power at all. If I plug the power cable to the monitor anything respond, even the power led doesn't turn on. So I decide to open my monitor an verify the power supply board hoping to find some bad caps in the board. But unfortunately all the caps in the power board looks good. Even I test directly on the board with an ESR and seems to be no problem on them. But the Monitor no power on. I notice that I have some caps with the same specs but different brands, I don't know if that could be the problem their tops are flat.

So I really need some guidance here with this. Here are some pictures of the board.

http://sdrv.ms/14NK1J1

[budm]

Re: Viewsonic VG2230wm no power

What voltage are you getting at that main large filter cap, measure right at the two legs, it should have about 160~170VDC. Just be careful not to touch anything with your hands or body since you are working in the HOT side of the circuits.

[snakezz]

Re: Viewsonic VG2230wm no power

What voltage are you getting at that main large filter cap, measure right at the two legs, it should have about 160~170VDC. Just be careful not to touch anything with your hands or body since you are working in the HOT side of the circuits.

I measured it like you said with the power cord plugged and I read just like you said 168.8 VDC.

What next?

[budm]

Re: Viewsonic VG2230wm no power

Since this power board is always-on board, you can run the board by itself for testing, There is a black rectangle fuse on the secondary side of the power supply next to the multi pin connector that connects the power supply board and the Logic/Main board together. Is that fuse OK?
http://s807.photobucket.com/user/bud...ml?sort=3&o=14

[snakezz]

Re: Viewsonic VG2230wm no power

Since this power board is always-on board, you can run the board by itself for testing, There is a black rectangle fuse on the secondary side of the power supply next to the multi pin connector that connects the power supply board and the Logic/Main board together. Is that fuse OK?
http://s807.photobucket.com/user/bud...ml?sort=3&o=14

Ok, I tested with my multimeter and beeps my multimeter as sign that is good.

[budm]

Re: Viewsonic VG2230wm no power

Then check and see if you have voltage at both ends of the fuse, Black lead of the meter to the negative leg of any one of the filter caps in the secondary side, red probe on the fuse.

[snakezz]

Re: Viewsonic VG2230wm no power

Then check and see if you have voltage at both ends of the fuse, Black lead of the meter to the negative leg of any one of the filter caps in the secondary side, red probe on the fuse.

Tested! 5.05 VDC on each leg of that fuse. I measure it exactly as you told me with the negative black lead of my meter on a negative leg of a cap near the fuse in both legs of the fuse and read the same.

[budm]

Re: Viewsonic VG2230wm no power

OK, so is this voltage being measured with the main board connected to the power supply board? If it is then we need to check the voltage regulators on the main board next.
Please post the pictures of the main board next.

[snakezz]

Re: Viewsonic VG2230wm no power

OK, so is this voltage being measured with the main board connected to the power supply board? If it is then we need to check the voltage regulators on the main board next.
Please post the pictures of the main board next.

No! I measured this voltage of 5.05 VDC with the power supply board disconnected from the main logic board. Do I need to do it with the main board connected to the power supply board?

[budm]

Re: Viewsonic VG2230wm no power

Yes, so we can tell if the 5V will remain or drops out due to it is heavily loaded down by the main board.

[snakezz]

Re: Viewsonic VG2230wm no power

I have added a picture of the main logic board. But Im not sure of which component is the voltage regulator.

Here is the picture
http://sdrv.ms/14NK1J1

[snakezz]

Re: Viewsonic VG2230wm no power

Yes, so we can tell if the 5V will remain or drops out due to it is heavily loaded down by the main board.

Ok I have test the Fuse again with main logic board connected and still reading 5.05 VDC in the Fuse.

So how I test the voltage regulators in the main board?? they are the 3 leg ones??

[budm]

Re: Viewsonic VG2230wm no power

Yes.

[snakezz]

Re: Viewsonic VG2230wm no power

Yes.

This is the mainboard, which one here do you think is the voltage regulator.

[mariushm]

Re: Viewsonic VG2230wm no power

Those that say 17-33 are LD1117 fixed 3.3v regulators. Instead of "LD", it can be anything else, it's a generic voltage regulator.

U9 is also a fixed voltage regulator, again a 1117 but a fixed 1.8v voltage regulator this time.

Put the multimeter on DC voltage. As you look at the chip with the text the way you can easily read it, the pins are arranged like this: GROUND, OUTPUT, INPUT. On the regulator with only two pins soldered to the board, the one that's in the air (the output) is also connected to the large tab.

So between GND and OUTPUT, you should have about 3.3v for the 3.3v ones, 1.8v for the other one. Between ground and input, there should be at least 1-2v above the output voltage... I would guess around 5v for the 3.3v regulators and 3.3v for the 1.8v regulator.

[snakezz]

Re: Viewsonic VG2230wm no power

Those that say 17-33 are LD1117 fixed 3.3v regulators. Instead of "LD", it can be anything else, it's a generic voltage regulator.

U9 is also a fixed voltage regulator, again a 1117 but a fixed 1.8v voltage regulator this time.

Put the multimeter on DC voltage. As you look at the chip with the text the way you can easily read it, the pins are arranged like this: GROUND, OUTPUT, INPUT. On the regulator with only two pins soldered to the board, the one that's in the air (the output) is also connected to the large tab.

So between GND and OUTPUT, you should have about 3.3v for the 3.3v ones, 1.8v for the other one. Between ground and input, there should be at least 1-2v above the output voltage... I would guess around 5v for the 3.3v regulators and 3.3v for the 1.8v regulator.

Correct!! here is a picture with results by each pin. I did the test with the mainboard connected to the powerboard and the power cable.

No idea what should be wrong?

[snakezz]

Re: Viewsonic VG2230wm no power

Yes.

After read the voltage in the regulators in the main board. It is normal that regulator in the left side read 4.82 VDC in the input pin??

Please help don't know what else to do.

[snakezz]

Re: Viewsonic VG2230wm no power

I'm including better top view pictures of both side of the PS board and logic board, in case somebody need to see them.

I really need help on this.

[budm]

Re: Viewsonic VG2230wm no power

4.82V is on a low side but the main board IC does not run directly off the 5v power supply but from regulator. At this you will need to locate the service manual for this version of the main board to do more probing.

[snakezz]

Re: Viewsonic VG2230wm no power

4.82V is on a low side but the main board IC does not run directly off the 5v power supply but from regulator. At this you will need to locate the service manual for this version of the main board to do more probing.

So you believe that the Power Supply board is not the problem?