CurtPalme.com Home Theater Forum

[Curt Palme]

This has bugged me for years, and since it happened again today, someone needs to 'splain this to me.

I've installed a number of CRT projectors into bars over the years. I've installed 100s of Zenith PRO 851/Sony 10 XX series, and I've gotten the expected 10K hours out of the tubes. Most bar owners stretched this to 15K to 20K hours, and of course the sets looked like crap past the 10K mark, etc.

Now, I inherited a porno theater customer years ago, and they'd bought a Barco 801s new, and I finally converted them to two BG808s after the 801 had 21,000 hours on it. to my surprise, the 801s, while worn, didn't have tubes at a '2' condition as you'd expect, with an Inline line doubler, the tubes were rated maybe a 6 or so. It was more the focus than the emission that got them to swap the sets. Now, this place ran 14 hours a day, 365 days a year. I had the two BArcos in there for about 4 years, they wanted one for backup, but they ran each set about 10-14 K hours or so, and when I pulled them out, the tubes were still in decent (6-7) shape.

Today I went to a sports bar that I'd sold an 808 to with a DVDO line doubler. I put in a transcoder and went HD with them. I could tell the tubes were worn, as the pix was reddish, so I bumped the G and B gains, and backed off the reds. After a convergence, I stood back, and HD looked good. Not great, but certainly OK for pub use. The manager noticed a b ig difference in detail in jumping rom the DVDO to the HD signal.

So I pulled up the hour meter. 41K. I installed the set at I think 18 K hours with new tubes. SO these tubes have well over 20K hours, and from looking into the lenses, they are at a 6-7 scale for the G and B, the red is probably an 8-9. They run maybe 5-6 hours a night, contrast and brightness are run at 70 right now.

So the question is, why do line doubled sets seem to run forever, well past the expected 10K hour mark? Why do industrially used Barcos and Marquees seem to wear faster, when they are run well past 480i as well?

I should have the answer to this, but I don't.

[Curt Palme]

This has bugged me for years, and since it happened again today, someone needs to 'splain this to me.

I've installed a number of CRT projectors into bars over the years. I've installed 100s of Zenith PRO 851/Sony 10 XX series, and I've gotten the expected 10K hours out of the tubes. Most bar owners stretched this to 15K to 20K hours, and of course the sets looked like crap past the 10K mark, etc.

Now, I inherited a porno theater customer years ago, and they'd bought a Barco 801s new, and I finally converted them to two BG808s after the 801 had 21,000 hours on it. to my surprise, the 801s, while worn, didn't have tubes at a '2' condition as you'd expect, with an Inline line doubler, the tubes were rated maybe a 6 or so. It was more the focus than the emission that got them to swap the sets. Now, this place ran 14 hours a day, 365 days a year. I had the two BArcos in there for about 4 years, they wanted one for backup, but they ran each set about 10-14 K hours or so, and when I pulled them out, the tubes were still in decent (6-7) shape.

Today I went to a sports bar that I'd sold an 808 to with a DVDO line doubler. I put in a transcoder and went HD with them. I could tell the tubes were worn, as the pix was reddish, so I bumped the G and B gains, and backed off the reds. After a convergence, I stood back, and HD looked good. Not great, but certainly OK for pub use. The manager noticed a b ig difference in detail in jumping rom the DVDO to the HD signal.

So I pulled up the hour meter. 41K. I installed the set at I think 18 K hours with new tubes. SO these tubes have well over 20K hours, and from looking into the lenses, they are at a 6-7 scale for the G and B, the red is probably an 8-9. They run maybe 5-6 hours a night, contrast and brightness are run at 70 right now.

So the question is, why do line doubled sets seem to run forever, well past the expected 10K hour mark? Why do industrially used Barcos and Marquees seem to wear faster, when they are run well past 480i as well?

I should have the answer to this, but I don't.

[WanMan]

I would imagine high-electron bombardment of the metal halide (MH) molecules is non-linear in their ability to break molecular bonds and thus create 'wear'.

If you got X number of lines generating Y light output and then compare it to 2X to generate the same Y output then I'd imagine the impact to the MH molecules to be less, and probably below a threshold that imposes a noticeable condition over time (say, Z period).

Imagine throwing N number of electrons at a MH molecule vs. 1/2N. Purely guessing, of course.

[_in_peace_]

I't must be the porno that goes very gentle on the tubes

But a line doubler in the end is similar to higer resolution's? perhaps not then

[ecrabb]

I think Wan's got the right idea. Phosphor electron beam exposure is a function of two things: Beam current and scan velocity (time). Think of the electron beam like an airless paint sprayer. Move the gun fast, and you put down less paint (with a smaller spray pattern); move it slow, and put down more paint (with a larger spray pattern - and with gaps).

For simplicity's sake, let's compare 480p and 1080p. 480p is 31.5khz and 1080p is 67.6khz. So, at 480p, each scan line takes about 1/31,500 of a second. At 1080p, that same single swipe of the phosphor happens in 1/67,500 of a second - or less than half the time.

Now, it's not quite linear because you have scan line gaps (or overlap) due to beam shape, etc... But, assuming similar beam current levels (contrast), I'd expect similar phosphor wear at 5000 hours on a 480p machine that you'd see at 10,000 hours on a similar machine running 1080p.

You can see this effect even on a multi-scan CRT monitor. Run at 640x480, and the image looks pretty damn bright (but with pretty good sized scan line gaps). Switch to 1600x1200, and the image gets more solid, but MUCH less bright overall.

SC

[dturco]

SC, Thanks for that analogy. The paint sprayer brought it right in to focus for me.

With that said, does this mean running 1080i will be "Brighter" than 1080p? Or at least be perceived as more light output?

[Curt Palme]

[Curt Palme]

[ecrabb]

Geek alert!!! Here's some funny trivia...

I just plugged the values into an Excel spreadsheet and calculated beam velocity. I assumed a 7.5-inch wide scan line (not sure if that's reasonable or not), I get 224mph (362kph) and 479mph (777kph) for 480p and 1080p, respectively. 479mph/777kph... Wow!

SC

[ecrabb]

[Curt Palme]

Tough to say of course, but I can't imagine some end user in a gov't facility running a monitoring system getting into the remotes and pushing them to 100/100 contrast and brightness. I have seen that happen in bars though. Good for business, selling them tubes every 18 months.

[Curt Palme]

Tough to say of course, but I can't imagine some end user in a gov't facility running a monitoring system getting into the remotes and pushing them to 100/100 contrast and brightness. I have seen that happen in bars though. Good for business, selling them tubes every 18 months.

[macgyver655]

I'm not going to say that everything I say here is fact but I'm working off memory here. Scott I'm sure can correct and/or verify.

The heater emits electrons that must strike the phosphor to make it glow and emit light. The heater does not shoot these electrons out with force. The high voltage charge on the tube face attracts them at a constant velocity. I'm pretty sure this velocity does not change because you would have to vary the high voltage for that. The intensity of the glow is based on the volume of electrons. No electrons, no glow. Lots of electrons, lots of glow.

Now when large volumes of electrons are used to make more glow for an extended period of time, it generates more heat which if not reduced will cause the phosphor to brown, such as baking. Different phosphors can withstand more heat then others before burning.

I'll start with this until anyone wishes to comment.

[ecrabb]

Mac,

I wasn't referring to the speed of the stream of electrons in the beam itself... That speed would be REALLY fast - in the ballpark with the speed of light, I'd imagine - or some good percentage of that.

Instead, the changing velocity I was referring to (that changes with scan rate) was the horizontal scanning of the beam spot, or the horizontal linear deflection velocity of the spot on the tube face. Slower - more phosphor exposure time. Faster - less phosphor exposure time.

SC

[perisoft]

One would think that running 1080p48 causes less wear than 1080p72 - the phosphor is lit up for less time overall. Obviously, because 48p flickers and 72p doesn't. With 48p you're letting your eyes 'drag out' the length of the phosphor glow, whereas with 72p you keep 'painting over' faster than is necessary for your eyes to perceive continuous light.

To take this to its logical conclusion, imagine running at a 1hz refresh rate. It would obviously take a long-ass time to create any wear on the tubes. And if you run at 1000hz, so there's never ANY 'down time', it'll have to wear faster.

But... this might be altered by the PJ's behavior. Will the beam be more intense with lower refresh rates and less intense with higher ones, thus canceling out the effect?

I agree. Study is needed.

[macgyver655]

[dturco]

What about the simple question from the simple guy , 1080i vs 1080p brightness ?

[Tom.W]

1080p should appear brighter then 1080i but it is more a visual perception.

[macgyver655]

Curt, before I add any more speculation to this, what res are you saying wears faster from what you've seen?

[Nashou66]

I think Ken Whitcombe proved 1080p is Brighter that 1080i by measuring with his light meter. the reason be , since its a progressive scan image and all the phosphor is lit up compared to interlaced where only half is lit at any one moment in time. This was explained last year at Cliffs meet by Ken.

Athanasios

[ecrabb]

Yeah, there's no perception about it... 1080p is definitely brighter than 1080i, and yes - Ken did prove that with a meter. If you wanted 1080i to be as bright as 1080p, you'd need to crank the contrast to do it (and probably lose some spot sharpness in the process, depending on where you started).

SC

[dturco]

I don't particularly care 1080i or 1080p. I just want to make sure that using 1080p will achieve the most Output-Brightness. Since using 1080i shrinks my image ever-so slightly which I find very strange because its the width that pulls in not the height.My limited understanding is that both are 1920x1080 but at double the frequency for 1080p. 1080i is 33.75hz/ and 1080p is 67.5? and both have the constant of 59.5hz?

But more so that I would have to move GOZER forward even when using 95H 1080i setting compared to the 90H setting for 1080p.

Weird huh?

[Curt Palme]

[Curt Palme]