CurtPalme.com Home Theater Forum

larryp · Joined: 24 Jan 2012 Posts: 252 Location: eden prairie mn

What wears a tube faster, hi Brightness or contrast?

barcodude · Joined: 14 Jun 2014 Posts: 169 Location: The Netherlands

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Brightness = low level, setting the low end of the grey scale, contrast sets the high end of the grey scale.

Contrast affects phosphor wear the most.

Phosphor wear is due to a combination of drive level, temperature, and duration. You could burn a tube to toast with a very low contrast level, but it would take many years to do it. More likely the cathode would be depleted before you toasted the phosphor under those conditions.

If you had a tube to waste for the experiment, say one that's already well worn, you could drain the coolant out of it until it's only half full, then run a full white raster on it at high contrast. The top half, lacking coolant, will heat up and the phosphor will
wear very, very quickly. But it may heat up so much that the glass breaks from thermal stress.

You could burn a tube in a matter of hours if you ran it with no coolant.

I'm sure someone here has had that happen to him.

barcodude · Joined: 14 Jun 2014 Posts: 169 Location: The Netherlands

so what are the best settings? 50 contrast 50 brightness or does it depend on tube wear?

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Guys

Nothing kills a tube faster than high filament voltage, as Marquee owners discovered back in the 1998 range. A supplier had saved three cents and put a cheaper part in the low voltage power supply, and when that part changed value the filament voltage fried the guns. If you want the brightest Marquee on your block, just try ten volts on the filament!!!!!

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I don't consider cathode stripping to be quite the same thing as tube wear. One happens at one end of the tube, the other should NOT happen at the other during the normal expected life of the tube.

What's the best contrast and brightness setting?

Whatever it takes to put your projector into proper calibration. It's different for EVERY projector and it's pointless to guess
what's best for yours. You need to go through the setup guide and adjust by test patterns according to the directions.

Settings even change depending on the signal characteristics of different input devices.

Settings and calibration are a complex issue. You want a simple "50 and 30" type answer but that answer is going to be wrong for your projector.

At the very minimum, you need to read the Marquee installation manual and use the internal test patterns to set the grey scales
for each channel (red, green, and blue) and then balance them out so the greyscale pattern looks like shades of grey from the black
all the way to the white, without any color shift anywhere on the pattern. But for most people it's difficult to set a neutral grey
by eye. So invest in a calibrator. A Datacolor Spyder will be sufficient.

barcodude · Joined: 14 Jun 2014 Posts: 169 Location: The Netherlands

i got a bg 801s from a dutch like e-bay for only 60 euro's (+/-40$) so even investing in such a high end thing is a little bit over doing it and i already got a resonable picture from following:

http://www.curtpalme.com/ES_Tube_Projector_Gray_Scale_Adjustment1.shtm

and suprisingly low tube wear on a 20.000+ hour pj (think they were muted a lot and it's more chassie hours than tube hours)