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Discussion Starter · #1 ·
When I am questioning sometimes unknowledgeable sellers about CRT condition, what is it reasonable to ask for in regards to tube condition? How should I describe tubes in acceptable condition? Obviously no localized burned in pattern, but what is normal visible discoloration of the raster area?


Thanks
 

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Good question. I really do not think there is a definative answer. Clearly, if you look in the face of the tube and the raster area is darker than the rest of the face this constitutes visible wear (a partial burn?). Dark streaks in this area would be a severe burn. Most who see any discoloration on a tube face would describe the tube as being burnt. A tube could be old, its brightness deminished by say 50% without the tube being visibly burnt. :)Its 2AM and I am burnt. :)My tubes are fine.:) AGIASB
 

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Noah,


It's tricky. Case in point. I often buy AmPros which are the same models as what I use just to have more parts projectors on hand. I can only have a very cursory examination of these before I buy them and so never really know what condition they're in before I get them home.

Earlier this year I bought one (7") and when I got it home I discovered that it only had about 500 hours on the CRT timer and was making a brighter and better picture than any 7" AmPro I owned (of about a half dozen of the same model). I was so happy with it that I took down my existing projector and replaced it.

A couple days later after watching two or three movies I put on "The Beach". I then noticed in the scenes in which the beach sand goes all the way across the picture that the beach looked darker on the left half than on the right. Once I saw this I then started to see a difference in color from left to right in most all bright scenes.

Even though the tubes had so little mileage the previous owner had let an image slightly burn the left half of the tube faces (all three tubes).

It was such an even wear pattern that it was not really noticeable at first. But once I did notice it my eyes could never avoid seeing it again.

Needless to say it was a great disappointment. I took that projector back down again and it's now on the parts pile.


I don't think it's going to be easy to rely on an unknowledgable seller to be able to always reveal wear or burn. Frankly for this reason I would never even consider paying real money for a CRT projector when buying it sight unseen from a situation like an online auction. Not unless the seller in question is someone known to be able to provide an accurate appraisal of tube condition. It's just too risky.


The few CRT projectors that are originally purchased only to display home theater images are probably going to be okay. But unfortunately the lion's share of these things were used for data display and the institutional users gave little concern to preventing tube wear and burn. The AmPros I own fall into this category and when I receive them more often than not they have one or more unusable tubes.


Bob
 

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Here's my experience with wear vs burn, as I had an NEC xg135 that had wear.

First look at the tubes with a flashlight, (PJ off) do you see any signs of discoloration? If the answer is no, then you don't have burn...now fire up the PJ open the raster and display an all while test pattern. If the whole test pattern is a uniform white then you have no wear...if however, you have an area within the test pattern that is tinted Blue, Green, or Red then you have tube wear on the tube that is the color of the tint.

On my old xg135 it was a Blue tint, so that PJ had wear on the Blue tube.
 

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I have a heat question. In all these pictures, I see the projector mounted close or flush to the ceiling. Does this allow adequate ventilation? I have a Sony 1271 in mounting and the installation manual says to leave some space when you ceiling mount it. More to the point, there is a picture of the bottom of the projector with a rectangle marked out. Underneath it says, "There are ventilation holes in the area marked with oblique lines. Do not block this area". Is this unique to my Sony, or is it something I don't need to worry about.


- Brian
 

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Discussion Starter · #8 ·
Boy, am I glad I asked about this; I was under the impression that some light visible discoloration was normal, but apparently even what look like pristine tubes can be worn.


Thanks very much, guys, this was very helpful.
 

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I think what Robert is describing is a special circumstance where the "burn" not wear was of a pecular manner.

That said, I totally agree with him that purchasing a CRT from an inexperienced seller who doesn't know how or doesn't take the time to visually inspect the CRT's is relying an awful lit of faith.

All of the projectors I inspect have the lens's removed and a careful inspection of the CRT's with a light. That is one wat to see wear or burn in. It can be deceiving to try and do it with the lens's on, and they are easy enough to take off. Second thing to do is get a white screen, like the Sony start up screen, and look into the lens at the CRT through a blank CD. That will reveal any other problems that couldn't be seen with the visual.

Wear is normal as the tube ages and will show up as a gradual darkening of the phospher. Burn is just that and will show up as something that has been etched into the phospher unevenly. And as Bob pointed out, it doesn't have to be a point or a line, but could be a larger area.
 

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Of course it can go the other way too. I bought (or rather traded for) a BG808s sight unseen. When I received it and first put power to it I looked at the total run time and it was showing 23,000 hours. At that point I threw up my hands in disgust because I just knew the tubes were toast.

Then I put up a white field and was shocked to discover that it was exhibiting absolutely no sign of visible tube wear or burn. What a rush!


Bob
 

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Do not confuse tube wear and "hot spotting".

Tube wear will show up as a distinct pattern, square or rectanglular, and is in a set position in the screen.

New tubes will have none of this.

Hot spotting is seen when using a screen that has high gain, it shows up as "areas" of the screen that are usually either Red or Blue, and as you move your position from side to side the hot spots move with you.
 

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"Burn" is common with computer sources (static). On video sources it should be "wear".


I have yet to see "burn" on a video only CRT, unless, there was a static image left on for a very long period of time...
 

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Excessive wear = burn


I have seen many PJ's offered for sale with various wording, ie: slight wear, minor burn in.


When I hear burn I think of text burnt into the tube. When I hear wear I think of even video wear that is tolerable and un-noticed to the average viewer.
 

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Quote:
When I hear wear I think of even video wear that is tolerable and un-noticed to the average viewer.
Wear which results exclusively from displaying a video image will be more uniform and more tolerable. But it's still no picnic. Unless you position the new image exactly within the worn area (not always ideal) you'll see color shift where it overlaps. It might be seen as subtle at first but after extended viewing it starts to stick out like a sore thumb.


Bob
 

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Quote:
Originally posted by KennyG
...if however, you have an area within the test pattern that is tinted Blue, Green, or Red then you have tube wear on the tube that is the color of the tint.

On my old xg135 it was a Blue tint, so that PJ had wear on the Blue tube.
I thought that a worn tube would emit less or degraded light in that area.


Therefore a projector with just a blue tube with wear or burn would display a white field with more red/green, not blue, eh?:confused:
 

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Perhaps that is correct, but in the case of my xg135, when I put up an all white test pattern, that pattern came up as a 4x3...inside of it was a 16X9 area that was tinted blue.

I'd assume that meant Blue wear, or I was told that was blue wear.

If what you say were true, that means both the Red and Green would have had to wear...isn't the Red usually last to wear?
 

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I aggree,

When a tube burns or ware's it is not going to produce either not as much light or no light in a specfic area. That is what makes it possible for you to see burns in the first place, there has been some cases that burns are obvious and the tube face is completly black at specfic aspect ratio shapes. It might be possible to do a search on this subject, someone posted cool pics of variously burnt tubes a while a go.


I have seen a DWIN HD700 that was left on with a DVD's menue runniung for a whilel that caused the text to burn in. It looked as though there were light stains on the screen when bright scenes were displayed. From time to time you could almost make out shapes of letters if the scens were long enough. Needless to say this unit has been sold to a guy that has a dedicated room and I dont think he is going to be too happy when he finds out the image looks "funny" from time to time. It wa snot hard fo me to see and this guy is going from a SharpVision LCD to a pretty good CRT. We'll see what happens.


Vic

VR Audio Systems

Phoenix
 

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Real interesting thread guys. A great issue of semantics. For me once I can see non uniformity in a tube when it is lit, (a darker square or rectangle where the image was on the tube face), it is time IMNSHO to replace the tubes. With VDC in LA, this $1500 for 3 non LC tubes and $2100 for 3 LC tubes. Plus the cost of tube removal and replacement and machine set up. Once done, assuming you do not burn a static image in by leaving the machine on with a static image for an extended period of time and assuming you do not push contrast too high, your tubes should last a long long time making this expense unnecessary again. Refurbish the tubes once and you essentially have got a new machine cheap. Hell Alan would say affordable. When replacing the tubes your video tech can clean connectors, resolder where heavy parts may be weakening connection and change 10 or 20 caps which may be aging. Not expensive.
 

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Exactly, Mark.

Doesn't much matter whether you call it wear or burn. Both result in a discoloration of part of the phosphor face and it's never very pleasing to look at in the projected image.


If it sounds like some of us are putting a lot of emphasis on this it's only because it can spoil otherwise very good performance in a CRT projector. And I have a sneaking suspicion that many units are purchased without the buyer knowing of it until he/she has spent the money and taken delivery of the projector.


Bob
 

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Reminds me of when I purchased my 9500LC on e-bay with tubes supposedly in good shape (for $3K) and all 3 tubes needed replacement. Set me back $8400 for the tubes (before the days of LC tube refurbishment by VDC). Even though, I ended up with a refurbished 9500LC with new tubes for about $13K. Fortunately, to me (using Alan's favorite word), it was affordable but significantly more than I was planning to spend.
 
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