ViewSonic VA1930WM VS11354 won't power on

[gustagen]

I just rescued a ViewSonic VA1930WM model VS11354 LCD from someone who said it "crapped out" on them yesterday. They had it in the trash and I decided I would tackle fixing it.

It has a ILPI-025 Rev. C dated "2006.07.28".

The unit will not power on. No screen activity, no power LED, no noises, nothing. I have disassembled it and done some very basic troubleshooting. I tested the power switch and the fuse on the power board. The caps all look ok, no bulging or leaking. No funny smells from the power supply board. I didn't see any bad solder joints. I have not looked at the other PCB.

Attached are two pics, front and back of the power board. I have _very_ limited experience repairing electronics, a cheapo multimeter, and a soldering iron. My experience with bad caps is replacing the visibly leaky ones. I have no experience with "testing" them. Anyone have suggestions for what I do next? Thanks!

[retiredcaps]

Re: ViewSonic VA1930WM VS11354 won't power on

no power LED

1) On CN801, measure DC voltage on each of the 8 pins with respect to ground. You can use a ground screw for your ground (black probe). Report DC voltages for each pin.

If you have a manual multimeter, set it to 20V DC.

2) If no DC voltages are present (they all read 0.0V DC), then CAREFULLY measure the voltage across the blue Su'scon large capacitor. Put your multmeter on 200V DC and put your black probe to the negative leg and your red probe to the positive leg.

If you live in North Amercia, you should get around 165V DC.

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

Thanks for the quick reply! I tested the voltages at CN801 as you instructed. Here are my findings:

1 - 5.18 V
2 - 5.18 V
3 - 0.00 V
4 - 0.08 V
5 - 0.04 V
6 - 0.00 V
7 - 0.72 V
8 - 0.68 V

I had previously measured the large 100uF 450V cap. Tested again and it still reads 168.1 V. I am indeed in the US.

Thanks again for your help!

[smason]

Re: ViewSonic VA1930WM VS11354 won't power on

Hmm, sounds like maybe the other board has an issue.
Can you measure pin4 while pressing the power button, also photos of the other board may help.

[retiredcaps]

Re: ViewSonic VA1930WM VS11354 won't power on

The 5.18V DC indicates that the logic board is probably getting power. We will need to test the components on that board.

Post a picture of the logic board so we can suggest test points.

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

Just got back from dinner to find two more replies. Thanks guys!

I measured Pin 4 at CN801 on the power board while pressing the power switch. There is no change--still measures 0.08 V. I measured while momentarily pressing the power switch as well as while holding it closed.

I removed and photographed the logic board on both sides. It is labeled "ILIF-020 Rev. A". There are several caps on the logic board, none bulging or leaking, and no other immediately visible faults that I can see.

Looking forward to your advice on points to test on the logic board. Thanks again!

EDIT: Just want to add that I have had the LCD panel disconnected during all the testing. All other connections are in place and I had the power switch PCB grounded to the chassis.

[jetadm123]

Re: ViewSonic VA1930WM VS11354 won't power on

In the upper left of your logic board, try checking the voltages on voltage regulators U101 and U102. Leg numbers are silkscreened on board for each regulator. Measure and report voltage on each leg.

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

I set my multimeter to "20" on the DCV scale and checked the three legs each of U101 and U102 on the logic board:

U101
1 - 0.00 V
2 - 1.25 V
3 - 4.89 V

U102
1 - 0.00 V
2 - 0.41 V
3 - 1.25 V

Thanks!

[jetadm123]

Re: ViewSonic VA1930WM VS11354 won't power on

I set my multimeter to "20" on the DCV scale and checked the three legs each of U101 and U102 on the logic board:

U101
1 - 0.00 V
2 - 1.25 V
3 - 4.89 V

U102
1 - 0.00 V
2 - 0.41 V
3 - 1.25 V

Thanks!

Hmmm....I'm thinking that U101 may be bad. What's the part number of U101 and U102? The part number is usually followed by a dash and two-digit number like 18,33,etc. This number is the output voltage, ie, 33=3.3V

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

Wow, this forum moves fast!

U101 reads:

A1
AS1117L-33
80630 14

U102 reads:

A1
AS1117L-18
80630 87

So, U101 is 3.3V and U102 is 1.8V?

[jetadm123]

Re: ViewSonic VA1930WM VS11354 won't power on

Wow, this forum moves fast!

U101 reads:

A1
AS1117L-33
80630 14

U102 reads:

A1
AS1117L-18
80630 87

So, U101 is 3.3V and U102 is 1.8V?

Correct. From your previous measurement the output of U101, pin 2, was 1.25V. This output is fed to the input of U102, pin 3. Since the output of U101 is bad, then it also affects the output of U102. Replace U101. Also consider replacing U102, since we cannot determine whether it's good or bad at this point. These regulators are very cheap and are available at digikey.com.

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

Sounds like I'll be replacing both of those components at your suggestion!

I'm having trouble locating them on Digikey using the part numbers printed on them. I found another thread in the forums referencing a replacement for AS1117L-33 as 497-1241-1-ND. Here's what I find on Digikey for that part number:

http://search.digikey.com/scripts/Dk...=497-1241-1-ND

Am I on the right track? It looks like their manufacturer part number is LD1117S3CTR. If I hadn't found that thread, how would I search using the numbers printed on the component?

Also, do you suggest the "cut tape" or "DigiReel" package type? I'll be finessing these on and off with an adjustable pencil tip iron and desoldering braid.

Thanks again everyone!

[PlainBill]

Re: ViewSonic VA1930WM VS11354 won't power on

Sounds like I'll be replacing both of those components at your suggestion!

I'm having trouble locating them on Digikey using the part numbers printed on them. I found another thread in the forums referencing a replacement for AS1117L-33 as 497-1241-1-ND. Here's what I find on Digikey for that part number:

http://search.digikey.com/scripts/Dk...=497-1241-1-ND

Am I on the right track? It looks like their manufacturer part number is LD1117S3CTR. If I hadn't found that thread, how would I search using the numbers printed on the component?

Also, do you suggest the "cut tape" or "DigiReel" package type? I'll be finessing these on and off with an adjustable pencil tip iron and desoldering braid.

Thanks again everyone!

You are on the right track. 497-1241-1-ND is the item you need for the 3.3 volt regulator. The manufacturer puts these up on a reel of tape designed for a 'pick and place' machine. The full reel contains 2500 parts, the Digi-reel is reel with a shortened tape that would contain dozens or hundreds of parts. The cut tape is simply a short piece of the tape.

For the 1.8 volt regulator you need 497-6868-1-ND.

PlainBill

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

Great! I just placed an order for both voltage regulators. I'll report back with an update after I've installed the new parts.

Thanks again to all who offered their help!

[gustagen]

Re: ViewSonic VA1930WM VS11354 won't power on

SUCCESS!!!

I am writing this reply using my "new" ViewSonic VA1930WM LCD!

I received my replacement U101 and U102 voltage regulators from DigiKey today. I managed to remove and replace U101 as suggested by jetadm123. I was too eager to test the repair, so I did not replace U102 in the hopes that it was still okay. I put the essentials back together and plugged it into my PC. It fired right up and looks great, especially considering the price!

I can't thank everyone enough for their input and help! If you subtract the days lost to shipping, this monitor was fixed in one day thanks to several kind souls on this forum!

I hope that someone else with the same problem will benefit from this thread at some point.

Thanks again everyone! You guys ROCK!

[retiredcaps]

Re: ViewSonic VA1930WM VS11354 won't power on

I am writing this reply using my "new" ViewSonic VA1930WM LCD!

Good job. Good info and pictures help us provide quality answers from people like jetadm123, smason, and PlainBill.

[jetadm123]

Re: ViewSonic VA1930WM VS11354 won't power on

Excellent work! Yes, I agree that good photos are critical in helping members analyze the problem. Worst kept secret: members that provide great photos are usually the ones that get the best and fastest responses from members.

[3apa3a]

Re: ViewSonic VA1930WM VS11354 won't power on

Hello all !
Maybe you can help me ? I have the same problem - the unit will not power on. No screen activity, no power LED, no noises, nothing. PCB's are absolutely the same.

Voltages at CN801 are as topicstarter

U101 and U102 voltages looks good:

U101:
1 - 0
2 - 3,3
3 - 5

U102:
1 - 0
2 - 1.8
3 - 3.3

What can I do next ?

[PlainBill]

Re: ViewSonic VA1930WM VS11354 won't power on

Hello all !
Maybe you can help me ? I have the same problem - the unit will not power on. No screen activity, no power LED, no noises, nothing. PCB's are absolutely the same.

Voltages at CN801 are as topicstarter

U101 and U102 voltages looks good:

U101:
1 - 0
2 - 3,3
3 - 5

U102:
1 - 0
2 - 1.8
3 - 3.3

What can I do next ?

Good work so far. What is the history on the monitor? How do the caps on the power supply look? What are the voltages on the power supply connector?

The service manual is available here.

PlainBill

[3apa3a]

Re: ViewSonic VA1930WM VS11354 won't power on

Thanks for answer.
History of monitor is unknown
PCB's with all elements looks like new. I'm from Europe, so have 230V voltage.
As for diagram 2. No Power & Power LED Off, I checked voltage on IC802 pin6 and that is 0. I checked pin6 with GND.
But I have 5.2V on 1.2 pins of CN801...