CurtPalme.com Home Theater Forum

[RogerH]

I have read just about everything I can find on the topic of doing an intentional pattern burn to help even out and extend a light/moderate CRT wear pattern. I'm ready to try it for real, and I would like to hear any stories of successes and pitfalls from anyone that has actually carried out the process.

I picked up a couple XG852s (Runco 991s) that were used stacked side-by-side in a 16x9 aspect. They must have been run fairly hard (harder than my own) in their 1300 hour lives and they were apparently very poorly set up up by the professional installer. The green wear patterns are undersize and off center horizontally and vertically. On top of that, they each have vertical keystone from being placed off center.

BTW, this effort is for education and experimentation, with the side benefit of possibly improving a low-time set of CRTs. I know that I could get superior results by just replacing the CRTs, but that isn't going to happen. These are parts machines for my good 852. Maybe more, if I'm successful.

Red and Blue CRT wear is very light and the tubes will be OK as-is, but I would like to extend the Green wear area. The existing wear is very uniform, but it is enough to give a color-shifted rectangle if I use a larger image area on the CRT face.

The good news is that I have been doing a controlled test burn on another (toasty) green crt and I believe that the wear-in time to match the candidate CRTs will be in the <100hr range.

I am planning on using Photoshop to create the burn masks from photos as others have apparently done. My strategy is to use a 2 tone, white-center/offwhite-border mask first (the shades found by trial and error), using the convergence and alignment controls to tweak the shape to exactly match the wear patterns until the projected (or through the lens) all-white image appears uniform. Then in photoshop I would replace the white with black and the gray border with green, and use this image to burn the CRT.

I was surprised to see that I could start to see my experimental burn mask outline become permanently visible after only about 10hrs of high contrast operation. That's good news for what I am trying to do here, but it is a little shocking to realize just how little it takes to damage a tube.

Comments, hints, and tips before I undertake this would be appreciated.

RogerH

[dvh99]

you will probably notice that the wear begins way before the wear frame, this must have been because contrast has been run harder towards the edges to keep a uniform brightness.
so your mask should have a rollof in colour from 255-255-255 to 250-250-250 and so on but this certainly is trial and error and the wear towards the edges is gradually so maybe you can enter certain values in photoshop for the rising values towards the edges starting at a certain point.
good luck but i would put in new tubes and forget all the hassle.

[Nashou66]

There was a thread on this last year with pics. I forgot who did it.

Athanasios

[RogerH]

Actually I see no wear outside the actual image area, either under external illumination or when turned on with a white or gray field. There is a very, very slight gradient from left to right of the trapezoidal wear area which I attribute to the vertical keystone. The left side (which is slightly shorter vertically) is proportionately slightly darker, as you might expect. I would probably use a solid mask to wear the entire border down to the lightest shade, then substitute a gradient mask for some additional time period, monitoring along the way.

I think these green tubes would be considered in pretty decent usable condition except for the undersize wear pattern.

I kept seeing references to a thread with pictures, but I don't think I ever found any pictures.