CurtPalme.com Home Theater Forum

Melifluonze · Posted: Thu Nov 13, 2014 12:38 pm Post subject: Phosphor burn rates...

So here's a question...

If I run one 9500LC at a contrast of 80 or so (running it hard) which looks just fine to me... versus running two 9500LC's at like, maybe, 50 or 60 contrast (or less???) does this significantly save the tube life?

Is phosphor burn an exponential curve, where if you increase the drive by 2X the phosphor burn rate increases by 4X?

Is there actually some point where the phosphor doesn't burn, but is still bright enough to be usable?

- M

cosaw · Posted: Thu Nov 13, 2014 4:09 pm Post subject:

What type and size of screen you got? What's your ambient light control like? What colour carpet, ceiling and walls have you got? I'd address all those factors before driving your contrast hard.

I've no experience of an Electrohome or 9" machines but I don't know why you've got to push em so hard? I don't know, maybe 80 isn't hard for an Ehome? I thought with tubes this size you could just take things easy? Surely you're gonna get bloom that will compromise your resolution? Anyway to me I'd think running at 80 instead of 50 would increase, rapidly, your wear rate.

Running two at 50 has got to be better but I don't like the complexity. If I HAD, two Ehomes and all the rest of the equipment I'd probably do it but you've got to decide at what point you want to stop tweaking and watch a film - I know that's a hard thing to strike a balance with, trust me! Smile

Just my thoughts.

Melifluonze · Posted: Thu Nov 13, 2014 6:29 pm Post subject:

Mindreader...

120" diagonal 16:9 screen. 1.0 gain
Black ceiling, walls, floor

60-70 is ok... 80 is good with a single projector...

-M

cosaw · Posted: Thu Nov 13, 2014 7:33 pm Post subject:

Edit: Just realised I've totally hijacked this thread, to everyone but Melifluonze, or those interested - please ignore the next paragraph, skip to the second. Smile

Well we obviously think along the same lines. Congrats on the full black room - not a possibility where I am. Congrats also on the five subs full range per channel plus two additional subs - my dream but again not possible. I ran stereo full range with two reasonably hi fidelity, sealed, home built subs, Q=0.707 (Two 12" Adire Shivas that found there way across to the UK - I wanted 15"ers but again not possible.) The subs aren't in action at the moment but my mains still go pretty low and are sealed also and as old as me at least (37). Houses are small you see, in the UK. Sad

My pj is a 7"ES Barco, coloured glycol which means colours are very nice - trying to get a Graphics 808s running. Screen is home built with canvas and paint, around 6.5 to 7 foot wide (left to right - not diagonal), can't be a gain of more than 1.0. As you can see I do things on a budget - even so I know what's relative quality and what is not. My crt projection setup is lacking (I still love it) but my stereo audio is not. Again 5.1 is not gonna happen in this house but the wall of sound that my stereo system puts out has always compensated and reminds me of the cinema I used to go to when I was a kid.

Anyway getting off topic. Maybe a bit more screen gain would help. If your theatre only sits one or two, then - smaller screen, sit closer, move your speakers to accomodate (oh yeah - and the projector Smile

) . I've satisfied myself with my diy screen knowing that it shouldn't really hotspot and it cost nothing. I'd love to paint my room black but, shall we say, it's a communal living space. Rolling Eyes

**AnalogRocks** · Posted: Fri Nov 14, 2014 5:03 am Post subject:

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Itll depend more on the material you display, if you display dark movies all the time itll wear less on 100 contrast than it will if you watch bright movies on 60 contrast.

Its hardly worth the thought, just enjoy it the way you want to, get a spare green and blue tube if you feel its going to be an issue Wink

cosaw · Posted: Fri Nov 14, 2014 9:07 am Post subject:

Analog, the first step is standing up and admitting you've got a problem. Well done!

Yes if you can stack up on tubes like Case says then I don't suppose you have to worry. Just make sure you max out the image, as much as is safe, to get the most output from your tubes anyway, hopefully you can notch the contrast down a few clicks in this situation.

Squirt that stuff in your eyes that makes your pupils dilate! Wink

Melifluonze · Posted: Fri Nov 14, 2014 11:42 am Post subject:

So funny... and so true...

I'm dropping the stack idea. Side by side means I'll be burning weird rasters and putting bad loads on the electronics. If I find a way to literally stack some day (top/bottom) I'll do it then.

- M

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

I wouldnt worry about the wierd shapes or stress on electronics, itll hardly be an issue.

Melifluonze · Posted: Fri Nov 14, 2014 4:21 pm Post subject:

Actually, it becomes a significant issue if you want to use the projector in a different configuration because you have to set the new raster into the original burn. Been there, done that. Burning a trapezoid sucks later.

For example, if I were to decide to move back to one projector later, I'd have to move it back a few feet to get into the short side of the trapezoid I burned while running the side by side stack. That's no good.

Running the projector in the center of the screen and at the right height, with the largest and most square raster possible allows you have the greatest possible latitude when reusing the tubes.

Small, weird rasters make worthless tubes.

-M

cosaw · Posted: Fri Nov 14, 2014 5:19 pm Post subject:

I like things simple. I'd just like to have a 9" LC, colour filtered, projector with spares. That's just not gonna happen in the UK. With my bad back I can't even lug the empty chassis anymore. I try not to be a nostalgic person but I find it difficult to move with the times. I would like small, affordable, light weight projectors that throw a film like CRT image - I still don't think that time is here. But on the other hand I can pick holes in an IMAX image and be preoccupied with the image and miss most of the film - that certainly annoys me. We've still got a way to go with the the 2D image (let alone 3D). Sometimes we've just got to enjoy what we've got even if it's only a 7" ES machine (like me) - get the best out of it you can and be happy. It's hard - but one day I might actually live that philosophy.

Melifluonze · Posted: Fri Nov 14, 2014 7:00 pm Post subject:

Cosaw, I think I'm agreeing with you, especially due to my room limitations.

Doesn't mean I won't try blending, though... Razz

Melifluonze · Posted: Fri Nov 14, 2014 7:02 pm Post subject:

Put a winch in your ceiling...

cosaw · Posted: Fri Nov 14, 2014 7:21 pm Post subject:

Yeah the winch. It's doable I suppose. Unfortunately the older I get the less motivation I have. Need to start scaling things back, how many stereo hi-fi amps do I actually use out of my collection? They're just sitting there with the capacitors drying up - you get the idea. Rolling Eyes

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

You wont burn any major trapzoids into the phosphor with the distance back youll have the machines... The trapazoid will be so minor you will struggle to see it on the tube face. If you went back to one projector later, THERE IS NO REASON TO MOVE IT! It is allready installed and moving it will gain you nothing, unless youre fitting new tubes, which makes your point null again.

Youre making a mountain out of a mole hill. Do, or do not.

km987654 · Posted: Sat Nov 15, 2014 2:16 am Post subject:

Melifluonze · Posted: Sat Nov 15, 2014 2:47 am Post subject:

Hey Case... it's a mountain. I've got a tube set here I can't use because of an off center issue. One side of the burn is smaller vertically forcing a move back. So, from personal experience, it's a problem. I wouldn't want to do it to two sets at once.

I'll go wild on the blend... Smile

You guys must get your tubes real cheap! Let me know the secret...

-M

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Theyre certainly not that expensive these days... Red and blue are really quite cheap, green is the only one that pulls a premium, and its not like as if theyre all that dear either.

Those tubes you have there with uneven wear... Did you set them up yourself? Same type of tube with exact same type of lens? You mension personal experience, but its just leaving alot of unanswered questions for me here, especially if the answer to any one of the above three questions is 'no'.

If you went back to a single unit, there would be no great need to move the projector at all, having it offset from the screen is not going to affect the image all that much, so just leave it that way.

Melifluonze · Posted: Sat Nov 15, 2014 6:33 am Post subject:

I had the tubes in my old 9500lc and I moved. If I use a single projector I can get close to re-using the full raster.

I hear what you're saying... in other words, if you have to move it, then move it, or retube it... Wink

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

No im saying leave it offset!! It wont matter enough to notice it if its allready worn that way!!