So it says. Me, I've never had a problem either way. Turn it on and you get a double image until the program shifts the unit into 15KHz. Doesn't whine or anything, which would be a dead giveaway that something's not good.
This will depend on how the monitor is made. On many fixed standard res monitors, the PLL for the horizontal oscillator won't be able to lock to 30kHz, so it'll lock onto every other edge at 15kHz, resulting in two lines of video being displayed on a single line for the double image effect. This should not be harmful to the monitor. However, just because it double-images most of the time doesn't mean it always will: if 30kHz is right at the edge of the loop bandwidth or VCO range, it may occasionally lock there. This would be more likely to happen on switchable monitors, but I can't say I've ever had it happen to me.
The PLL of some monitors, especially those designed for use at (or switchable to) medium res (25kHz horizontal scan), may be able to lock their PLLs at 30kHz. If this happens, bad things are likely to result (basically toasted horizontal stuff). It may NOT whine if this happens, so don't take a lack of "whine" as a sure sign that you're OK.
The technique commonly used to protect monitors like this is to halve the horitzontal sync when it's out of range or turn it off entirely. Halving it forces the double image thing, while turning it off entirely will result in video that's rolling in both directions as the PLLs on the monitor free-run. Either should protect your monitor just fine. I presume this is what the JPAC does as it's pretty trivial to program a micro to handle this.
All that said, the best off-the-shelf way to handle this would probably be to use a JPAC or similar. I can do it much cheaper (a couple dollars), but I doubt you want to deal with bare chips.
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Topic: 120v switch delay for monitor (Read 2682 times)
