Hi all,

I've been having a nagging problem over the last 15 months or so where the
blue tube on my Pioneer PRO-510HD never seems to completely shut off causing
visible blue hue during dark scenes . Hue is basically trapezoidal and
accompanied by inverted arc running along top of screen. This shape widens
somewhat when the 1080i (33kHz) scan rate is used, but its still there. With
a blank input selected and front cover off, the blue crt has a dim glow
about it while the red and green tubes are totally black. Also minor flashes
of blue randomly occur which are very distracting. All this is painfully
obvious when viewing dark programming in a dim room which is how I first
noticed it.

I've replaced low voltage PS (twice) without luck. Swapped video signals
with G drive board and problem remains on blue. Disconnected SVM coil - no
joy. After some research using Sams FAQ, determined that common elements
like H and V deflection, flyback, and chroma decoder couldn't be at fault
without affecting other guns. Only option left was mark and adjust SCREEN
(G2) pot. No dice, when raised too much screen went totally blue (with no
input), when lowered it made no difference. Lastly, tried changing Vref
setting at non-inverting input of video amp in the hopes that beam cutoff
(G1) wasn't being fully acheived at black causing a low level "leakage" beam
emission- again, no change visible.

I haven't swapped the driver card with another in the set yet since it would
be more complicated than I'm willing to undertake at this point given the
wiring constraints. This is also because another individual repoting this
*exact* same set of symptoms had a tech working on it with direct support
from Pioneer for months before essentially giving up. The guy then got the
schematics and first thing he changed was the driver card - but it wasn't
it. (He also changed dig conv, deflection and video ip assy all with no
luck.)

So, just wondering if anyone has ever seen a blue CRT go bad like this? I
would say I got about 3 years of trouble-free operation out of it before I
started to notice this behavior. Its not a common problem, in a year of
asking around I've only ever seen this one other person recently report the
same issue. Naturally, since replacing a tube isn't trivial, I want to be
absolutely sure before I go down this path.

Any comments or feedback greatly appreciated. My apologies for the lengthy
post!

Regards,

Doug