Viewsonic VG2030WM No Display

[tervel12]

Hello,

I have a Viewsonic VG2030WM LCD monitor that has no display. The backlight is on but I am unable to view anything on the screen.

I have checked voltages across the PSU, Logic board, and the board on the screen itself.

Everywhere I check I find 3.3v or 5v. The fuses (that I can find) on each board all seem fine and have voltage on both sides of them as well.

Any help is greatly appreciated. I also have the service manual if that would help out.

Thank you,

tervel12

[PlainBill]

Re: Viewsonic VG2030WM No Display

Hello,

I have a Viewsonic VG2030WM LCD monitor that has no display. The backlight is on but I am unable to view anything on the screen.

I have checked voltages across the PSU, Logic board, and the board on the screen itself.

Everywhere I check I find 3.3v or 5v. The fuses (that I can find) on each board all seem fine and have voltage on both sides of them as well.

Any help is greatly appreciated. I also have the service manual if that would help out.

Thank you,

tervel12

Do the backlights turn off when you push the power button? If they do (and the power LED turns off) the logic card and power supply are probably good. I'd check the fuse on the panel card - the long board at the top of the first picture. This will be a surface mount fuse.

PlainBill

[tervel12]

Re: Viewsonic VG2030WM No Display

The lights do turn off when I press the power button. The fuse on the long board at the top tests good. It has 5v on either side of it when powered up.

[PlainBill]

Re: Viewsonic VG2030WM No Display

The lights do turn off when I press the power button. The fuse on the long board at the top tests good. It has 5v on either side of it when powered up.

Aww, crud. That means there is a problem on the panel board. There is a square IC about 4" from the left side. What is the part number of that IC? Also, a good picture of the left half of the board would be a big help.

PlainBill

[tervel12]

Re: Viewsonic VG2030WM No Display

There are 2 square ICs on the board. The one about 4" in is about 4mm square and is labeled: AAT1164C AG6450 0736. The second one is about 14mm square and reads: AUO-030 027-FS 4V003.

I will try to get a real camera and take a better picture. I only have my cell camera at the moment.

Thank you for your help and speedy replies!!

[PlainBill]

Re: Viewsonic VG2030WM No Display

There are 2 square ICs on the board. The one about 4" in is about 4mm square and is labeled: AAT1164C AG6450 0736. The second one is about 14mm square and reads: AUO-030 027-FS 4V003.

I will try to get a real camera and take a better picture. I only have my cell camera at the moment.

Thank you for your help and speedy replies!!

The AAT1164C is the one I was interested in. That provides the various voltages required for the LCD panel. I would suggest checking all semiconductors in that area.

PlainBill

[momaka]

Re: Viewsonic VG2030WM No Display

I would suggest checking all semiconductors in that area.

And ceramic caps as well. Any ceramic cap that measures less than 30 ohms is suspect and the circuit it's in should be checked to see if that measurement makes sense.
A better picture of that area would also help.

[tervel12]

Re: Viewsonic VG2030WM No Display

Here are some better pictures (I hope).

I will check around that area as you suggested and report back the results.

Thank you.

[jetadm123]

Re: Viewsonic VG2030WM No Display

Here are some better pictures (I hope).

I will check around that area as you suggested and report back the results.

Thank you.

In photo 4, also measure the voltage on all pins of voltage regulators U1 and U4.

[tervel12]

Re: Viewsonic VG2030WM No Display

Here are all of the readings around the AAT1164C chip.

(Note: I measured across each of these components)

C277=1.98v
C93=4.74v
C92=3.3v
C29=0.45v
R11=0.45V
R10=4.27v
R70=0.0v
C91=0.02v
R23=3.74v
R22=3.74v
R61=1.04v
C95=0.16v
R62=0.16v
C90=0.0v
R71=0.0v
R72=0.0v
R66=0.0v
C94=1.24v

For U1 and U4 I measured to each leg from ground.
U1 Base=0.0v Collector=1.78v Emitter=3.3v
U4 Base=0.0v Collector=3.3v Emitter=.0v

(Hopefully they are labeled correctly. I measured them from left to right with the transistor at the top)

I have also included an enlarged picture of the area around U11 (AAT1164C).

Thank you.

[retiredcaps]

Re: Viewsonic VG2030WM No Display

For U1 and U4 I measured to each leg from ground.
U1 Base=0.0v Collector=1.78v Emitter=3.3v
U4 Base=0.0v Collector=3.3v Emitter=.0v

I don't know about the chip, but U4 should be outputting 1.8V DC. U1 looks correct.

With power off and lcd unplugged, see if U4 is shorted by testing pins 1-2, 1-3, and 2-3. Any reading under 30 ohms suggests it may be shorted.

[tervel12]

Re: Viewsonic VG2030WM No Display

My mistake, I got U4 and U1 mixed up.

Sorry, I know that doesnt help much when wrong information is given.

U4 Base=0.0v Collector=1.78v Emitter=3.3v
U1 Base=0.0v Collector=3.3v Emitter=5.0v

I am not reading any shorts on U4 or U1.

[retiredcaps]

Re: Viewsonic VG2030WM No Display

No worries about the mistake. I have definitely made my fair share and more on this forum.

Both voltage regulators look like they are working fine.

[tervel12]

Re: Viewsonic VG2030WM No Display

That's good to hear (about the regulators being good). So does that mean that U11 is bad possibly? Or is this just scrap?

[retiredcaps]

Re: Viewsonic VG2030WM No Display

So does that mean that U11 is bad possibly?

My intrepretation of what PlainBill and momaka wrote in post #6 and #7 is that they wanted you to test each individual component around U11. So if you see a SMD capacitor, check for shorts. Check the resistors to their stated value.

[jetadm123]

Re: Viewsonic VG2030WM No Display

If I understand the application circuit for U11 correctly, try measuring the voltage on the right side of diode D10 (located to the left of U1). Use a mounting screw as your ground for your black probe. You should get something like 12-13V. If not, then power off and unplug monitor and check D10 and any cap or resistor connected to it for shorts.

[tervel12]

Re: Viewsonic VG2030WM No Display

D10 has 5v on either side of it.

I checked some other components for shorts and D60 measures 2.5ohms across pins 1 and 2 (you can see it in the top center of the LCD3.jpg picture). The two components next to it (labeled D20 and D21) both measure 700 on the 2000K scale. L44 is what is stamped on the top of this component.

A little googling and that is a Schottky Barrier Diode. Could this be the problem?

[Th3_uN1Qu3]

Re: Viewsonic VG2030WM No Display

Mmm, that D60 sounds shorted. But it could as well be a dual diode and used with both diodes in parallel. Unsolder it from the board and measure again. If you still get 2.5 ohms then it's dead, if you get anything else it's okay.

[momaka]

Re: Viewsonic VG2030WM No Display

I checked some other components for shorts and D60 measures 2.5ohms across pins 1 and 2

That means either D60 is shorted or C61 is shorted. Probably easier to remove C61, so do that first and if the short circuit is still present between pins 1 and 2 of D60, then D60 is bad. I've seen these diodes withstand quite some abuse, though, so I think C61 is more likely to be bad. Once you remove C61, check it by measuring resistance across it.

As for D60 - it is indeed a Schottky Barrier Diode, consisting of 2 diodes inside in series, with pin 1 being the anode of diode 1, and pin 2 the cathode of diode 2. Pin 3 is cathode of diode 1 and anode of diode 2.

While you're at it, also check C20, C21, and C60 for short circuit (by measuring resistance across them). Check D10 as well (either with diode test or by measuring resistance).
Last but not least, measure the resistance between cathode of D10 and ground. Keep the negative probe of your multimeter on ground.

[tervel12]

Re: Viewsonic VG2030WM No Display

Thank you for the tips. I will check these things when I get back to work on Monday and let you all know.

Thank you for all the input and have a Happy New Year!!!