I am trying to res-erect a ViewSonic VG1930WM which shows no signs of life(no LED, no anything). I see no bulging caps. I have verified 14.7v and 5.19v from the power supply. I have attached a page from the LG L192WS manual which apparently uses the same control board(ILIF-020) as the ViewSonic. Pardon my sloppy notes on the schematic. My thoughts are that the voltage regulator U102 is bad. It is an AS1117L-18. I appreciate any input.
ViewSonic VG1930WM
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Re: ViewSonic VG1930WM
U101 should also be outputting 3.3V DC. You can test both U101 and U102 to see if they are shorted. Any resistance reading less than 30 ohms between the pins 1-2, 2-3, and 1-3 suggests a short.--- begin sig file ---
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Re: ViewSonic VG1930WM
Thank you for the response. I measured U101 and 102 in circuit. The lowest reading I got was about 400 ohms between pins 1-2 on U102.Comment
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Re: ViewSonic VG1930WM
Thanks for the idea. I have lifted the leg off the pad for pin 3 on U102. I still get 1.26v on the pad and 4.89v on pin 3 of U101. Maybe C101 is shorting out?Comment
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Re: ViewSonic VG1930WM
I missed the part where you are only reading 1.26v on the output of U101.
Something is taking the voltage low .Is anything hot to the touch
Al.Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!Comment
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Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!Comment
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Re: ViewSonic VG1930WM
I have a monitor right now with 2 shorted out voltage regulators on the logic card. So it isn't impossible that you have 2 bad voltage regulators? I realize yours are not shorted, but since U101 is outputting low voltage it is bad.
From what I understand of reading PlainBill's posts, a voltage regulator failing low is better than failing high and destroying other components with too much voltage.Last edited by retiredcaps; 11-20-2010, 02:42 AM.--- begin sig file ---
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We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
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Re: ViewSonic VG1930WM
There are two problems here. First, the schematic is wrong (or you made a mistake measuring voltages). The schematic shows both U101 and U102 getting power from the 5V supply. That is an unusual arrangement. Given other flaws in the schematic, I suspect it is wrong.
By the voltage measurements, U102 gets it's power from the output of U101. That is a common arrangement.
Either U101 is bad, or something is overloading the output. U102 appears to be good. One trick you can try is to apply 3.3V to the output of U101. If it comes up to 3.3V, the regulator is definitely bad. If it does not rise, something is overloading the 3.3V power rail.
You probably don't have a spare 3.3V power supply sitting around. Use two 'D' cells (flashlight batteries) in series. Fresh alkaline cells will provide about 1.6 volts each.
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: ViewSonic VG1930WM
Thanks for all the input. I never thought about the schematic being incorrect but it makes perfect sense when I see the input voltage of U102 is the same as U101 output. I was only able to get up to 3.1v with the batteries I have on hand(4 C's in a parallel series combo). When I apply the 3.1v to the output of U101 the voltage falls to 2.6v. Keep in mind that this test was performed with the input leg of U102 still lifted from the pad and the power on. Any advice from here is greatly appreciated.Comment
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Re: ViewSonic VG1930WM
Thanks for all the input. I never thought about the schematic being incorrect but it makes perfect sense when I see the input voltage of U102 is the same as U101 output. I was only able to get up to 3.1v with the batteries I have on hand(4 C's in a parallel series combo). When I apply the 3.1v to the output of U101 the voltage falls to 2.6v. Keep in mind that this test was performed with the input leg of U102 still lifted from the pad and the power on. Any advice from here is greatly appreciated.
PlainBillFor a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.
Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.Comment
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Re: ViewSonic VG1930WM
Just wanted to update and give thanks to everybody and especially PlainBill. The VG1930WM is back in service!! I replaced U101 (the AS1117L-33 regulator) and the old girl reciprocated with a blue led then a full screen picture. No problems after several hours. Thanks again.Comment
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