CurtPalme.com Home Theater Forum

[LOTREE]

I couldn't find anything posted on this but again my searching techniques may not be that good.

I've been doing my best prior to shutting off the projector to keep the phosphorus from staying hot, allowing the source signal to continue to be painted with a dark image to clean the face. I'd generally put the projector in standby, or used to at least, to prevent any signal feedback from displaying when powering off. Contrast is usually between 3-5, brightness 6-7 although now most is controlled via the computer which is another question in a second. I used to turn the brightness and contrast near zero before power off.

I may have put 100-200hours at best on the 4500 since I bought it used and even now I notice extremely faint 4:3 wear checking with a LED flashlight. The amount of 4:3 display is probably 5-10% of the overall usage and that generally involves power up and shut down, program control, anything I need to do to access the desktop prior to starting a movie. I don't use it for watching tv or full screen movies. If I shut down the computer like normal I get the big blue XP splash screen "Windows is shutting down" and then only the green tube is left with the final image that slowly dims out after 5-10min. Is there a way to eliminate this ghost image prior to turning the projector off? The red and blue tubes are completely dark after shutdown.


The second part to this is if I set the contrast and brightness as low as I need on the projector but tweak both in ZoomPlayer using FFDShow or the ATI graphic settings would that overdrive the tubes as if I just left both higher through the projector controls instead?

The next investment will certainly be a greyscale calibrator but for now I have to work with what I have.

Greg

[ecrabb]

Greg,

There is no reason to display one thing or another before you shut the projector off. There is no real active cooling of the glycol, so no cool-off period of any kind is necessary. The phosphor cools when you power down as well is at cools when you turn down brightness/contrast. Even if you're displaying a solid white screen of some kind, and shut off the projector, there is no different cumulative effect than if you turned down brightness and contrast and shut down.

As for the wear, it's entirely a function of brightness/contrast settings and the content you display. If you have contrast maxed, but always watch low-APL material, you'll have little wear. If you have contrast reasonable, but watch a lot of movies with snow (or bright red/green/blue screens), then you'll get wear. If you're seeing some faint 4:3 wear after you've only used the projector for 100-200 hours, then I'd say you must be driving contrast pretty hard. Where is your contrast control set when you're watching?

As for your second part, think of the contrast control like a volume control on an amplifier. If you turn it way down, there's nothing you can do at the source to make it any louder. Same with the contrast. Contrast controls maximum beam current, and whatever the max beam current is, nothing you can do with the HTPC will make it any brighter than the contrast control allows.

What's your screen size/material?

SC

[LOTREE]

I generally have the contrast set to 3-4, rarely 5 out of 10 so it's rather low to begin with.

The 4:3 wear might account for even less than I stated, most of it seen during tweaking, opening software and checking a few things online. I see no 16:9 wear at all and was mainly concerned with final image blasted at the green tube before the computer shuts off. Basically the projector doesn't clean the face with another frame as it would if it changed from a white to black scene in a movie. If I shut it off at that moment with a black image displayed the tube face would also be dark looking through the lens. I just feel as if this memory/ghosted image is damaging the tube face unnecessarily. It's not an issue of the tube/glycol actually being hot/warm and needing to cool down but rather keeping the phosphorus free of bright images before I turn off the power. I'll probably find the windows shut down splash screen and replace it with something else regardless.

The screen is currently 59" wide painted with Berh UPW. New DW will be here Monday.

[Mark_A_W]

What projector uses a 1-10 scale for contrast?


And I don't get the logic behind this thread. It will make no difference to the tube life. The green glows after shutdown because the phosphur glows - what do you reckon they make glow in the dark stuff out of?

Turning the projector contrast down and the source up is the same in the end.


And what's the point anyway? You didn't add the 4:3 wear in 200 hours, it came from the 4500hours.

Run it as hard as you can before blooming, watch a movie a few times a week, and the tubes will still be fine when the projector dies, or is replaced.

[LOTREE]

The projector is an Electrohome ECP 4500 with tube condition of 9 or near mint. They also use an adjustment digital scale of 0-10 for most settings, Contrast, Brightness, Focus, Color, Pin, etc.

The reason I'm asking is if it IS a problem and could it be causing premature wear, much like spot burn... it's fine when on and scanning the face but the moment you shut it off you can damage the tube. I also understand the fundamentials of how the phosphorus screen works and why it glows, that's not my question. I'm interested to know if at shut off and a static image is left imprinted on the tube face even for a second if that can cause more burn than if it was on scanning happily. Like I said, the projector can switch from an all white scene to complete dark, shut it off and not have the same memory effect.

[ecrabb]

Mark's probably right... You probably didn't put on the wear you're seeing last 200 hours... You're just now noticing it. Which tubes are you seeing it on? All three?

[LOTREE]

[ecrabb]

Nope, the only face cleaning that goes on in your house probably involves a washcloth.

You probably just notice it more because you see the decay much earlier in the decay cycle... When you turn the contrast down, the phosphor is decaying while you're turning down the contrast, so there isn't nearly as much decaying left to go by the time you hit the power button.

Blue and green worn together is normal wear, meaning average viewing wear. If it was all on the blue, I'd suspect a Windows desktop or whatever.

You can just "shut 'er down"!

SC