Question about ViewSonic PF790 19" CRT Monitor

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PF790 monitor picture issue

Hi, My PF790 had been unplugged/unused and stored away in its original box for a few months. I recently removed it from its box to connect it to a spare computer that we felt could be used as a bedroom HTPC system - for our bedroom, the PF790 could double as a decent size TV. Anyways, once I connected the monitor to the computer, it worked fine for about 10 minutes. I had not used the spare computer for some time either, so had to install few updates and reboot the PC a few times as well. During one of the reboots, the monitor simply stopped showing the picture. The green power LED light stayed green and did not turn orange even after the computer was turned off. I have even tried disconnecting the vga cable from the back of the monitor so that the only cable connected to the monitor is the power cable. Even then, the monitor power indicator led remains green - the LED does not turn orange or display a message on the CRT similar to "No signal - Going to power save mode". Another thing - when I turn the power on (whether or not vga cable is connected to monitor), I hear a very high-pitched/faint noise from the monitor. Finally, the 10 minutes that the monitor did work, for the initial few minutes, I had noticed the lower left and right corners were showing "discoloration"(?) similar to what one would see if non-magnetically shielded speakers were kept near a CRT screen. However, there weren't any speakers or any other sources of magnetism near the monitor or anywhere else in the room. I can do simple repairs (I've built computers, assembled/soldered together DIY-home theater speaker kits, etc), but haven't worked with CRT monitors - would appreciate any feedback on what could be the problem and whether the monitor is repairable or not. Sorry for the long post, but I hope the details can help someone provide an answer to whether I should even try repairing it or not and if its repairable, what would be a good starting point. Thanks and Happy Holidays, -Topper

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Re: PF790 monitor picture issue

Was it dropped? If so, it could be a board crack or damage to the CRT. Was it stored in an unheated garage, shed, or attic, etc.? Damp air or widely changing temperatures can cause condensation on the circuit boards. Minerals and other impurities can collect on the board via the condensation, leading to some nasty corrosion. Plus in my opinion, late-model CRT monitors are a real pain to work on. Many of them have so many shields and so many screws that before you get the board free to work on it, you're sick of messing with it! *grin* Then when you do some work on it and want to test it, you have to do a lot of reassembly first. I'm sure others will be tempted to jump in here and tell me how crazy I am, but unless they belong to a family member, I don't even work on them any more. When it comes to monitors, I only work on the flat-panel types. But if you go for it, look for electrolytic capacitors with bulging tops or leaking bottoms, bad board connections, etc. Good luck!

Posted on Jan 12, 2007

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