I just replaced all three CRT's in my Runco DTV-991 (NEC XG-851). I ordered all three tubes from Runco, got an NEC Red, VDC Green, and a VDC Blue.
The blue CRT came in a box that looked like it had been sent to another dealer and subsequently returned.
The packaging consisted of the usual foam at the face end of the box, but rather than the cardboard insert that protects the neck of the tube, there were 4 peices of foam surrounding the neck.
The serial # is on the box is 49294.
The ceramic support inside the tube is not the same color as the other two tubes, it is a brownish pink, where the other two are light blue.
The coating inside the neck is brownish, not grey.
There are obvious ripples where the new neck was attached to the older bell and face.
If you are wondering where this is leading to, here is the issue:
The Red and Green CRT's work flawlessly, the NEC has a slightly finer spot size, but both will focus sharply and hold the sharp focus with the contrast run all the way up to 100. Astigmatism adjustment with both was simple and the results are perfect.
Center focus is perfect and edge focus is the best I have ever seen it.
The blue tube, well this &%
[email protected]*() thing is giving me fits. Where to start:
1. The tube would not cut off unless I adjusted the black bias to a value outside the normal 2.5 +/- .1 volts.
2. The astigmatism was a bear, it's just barely OK after a major battle with it, but not at the level of the other two CRT's.
3. Focus degrades at high contrast levels, at 100 the blue crosshatch lines are easily 10 times the width of red and green. (I know blue won't focus as well as red and green, but the original blue tube was much better on focus, although somewhat worn).
4. The edge focus is terrible, in fact it can't be focused.
5. Color temperature tracking is off, I have to boost the blue bright bias and drive to much higher levels than the other CRT's adjustment.
My question:
Did I get one of the early VDC rebuilds from the days before they perfected the process?
Vern
P.S. Tube replacement procedure and setup info courtesy of Guy Kuo and Doug Baisey via AVS.