PF775 blank screen

Sep 25, 2007 3 Replies
T

Hey Folks,



I have an Viewsonic PF775 CRT monitor on an older computer. This is my linux play box/secondary computer (ie, I don't want to spend a bunch of money on). Went to fire it up and the monitor came up blank, though the power light still comes on. I read SAM's repair FAQ at

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as well as this brief article at
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Though I'm pretty comfortable with microelectronics (when I have a schematic), I'm out of my league trying to debug a CRT cold. Couple of questions though.



1) I have a 2 yr old son that may have managed to find the contrast/ brightness controls in the setup menu. I imagine though that the setup menu would still be visible even if these controls were set way out. Can somebody confirm this for me?
2) I've done a pretty close inspection of the main PCB looking for cold solder joints or signs of overheating. Is there any other simple steps I could take before I send this for recycling? I'm debating trying to probe the transistors for shorts, but would kindof be going after the problem blind. Any suggestions where to start?

The other clues I can provide are: a) Monitor was working fine last time I used it. The PC/Videocard works fine with other monitors. b) There is some sounds when I turn the monitor on as it powers up. It may be the degaussing. I can try describe these better if they seem relevant. c) Sometimes when I turn it off, there is a flash of blue light in the middle of the top 3rd of the screen.



Given that a 17" LCD is only $180, I don't think it would be worth the money to pay for a repair, but I may get a quote anyways. I love to both learn and tinker, so if I do get some insight I may really dig in. Certainly any opinions are appreciated



Thanks in advance for any help. TMFS



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H

at

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well as this brief article

Just to make sure it is the monitor, and not the PC to which it is attached, try a second monitor before assuming it is the monitor that is at fault.

Two-year-olds can do some wonderful things, maybe he/she can undo whatever they did .

H. R. (Bob) Hofmann

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T

at

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as this brief article

Sorry, should have noted that I have already tried a different monitor (which worked fine). I also hooked this monitor up to a known good PC just to be conclusively sure that it is the monitor.

Darcy

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T

at

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well as this brief article

Looks like the problem has resolved itself (at least temporarily). One of the things I did to try pinpoint the problem was to power up the monitor without a pc and look for the "input cable disconnected" warning. Initially the screen was blank, but I inadverdantly left it on overnight. Turns out it started to work of its own accord. Of coarse without a cable the monitor never went into sleep mode, so the monitor had warmed up to normal operating temp. I think this definitely points to a bad solder joint at this point. I suspect the problem will return shortly, so I'd still be happy to hear any thoughts on where to start with this problem.

While it was operational, I answered my first question. Regardless of the brightness/contrast, the user setup menu is always visible (at least on this monitor).

Thanks Again, Darcy

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