CurtPalme.com Home Theater Forum

[gjaky]

[stridsvognen]

[gjaky]

No comment.

[stridsvognen]

so the arc are going from the neck board, and to the aquadag.?

[Nashou66]

[Tim in Phoenix]

Guys

When the Marquees first rolled out in late 1992 the dealers were very excited. We installed the first twenty M8000s in three months, then the problems began. Streaks in the video or just dead tubes. Electrohome sent us dozens of neckboards to change out but those failed too. They halted all shipments of projectors for a month and spared no effort to identify the cause of the failures. Tube arcs were suspect, but how do you make tubes arc on demand to study the problem? The answer was lasers! They brought in some consultants, and they looked at things and returned shortly with some gear. By shooting the electron guns with lasers they got a tiny poof of vaporized metal, and they got an arc nearly every time. They identified the need to add diodes in certain points on the neckboards, and the next batch of neckboards had extra stuff tacked on everywhere. Those were not pretty boards but they held under arc, and foil layouts were redone to incorporate the diodes onto the boards.


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[stridsvognen]

[gjaky]

Probably Scott (tse) is the only one here who could give the most statisfactory answer.
Read here:
http://en.wikipedia.org/wiki/Aquadag

The driving of the tube is referenced to the ground that is on the VNB, so connecting the aquadag there would be the best solution, if you connect it somewhere else that means if any current flows there it elevates the ground of the VNB through its ground resistance.

In a CRT projector the ground loop is not that bad as is an audio amplifiers because of it's more complex structure, eg. focus and convergence have no real effect on each other, so the ground loop neither affects their function. But good surge protection is crucial, as everything near to the tube is endangered of high voltage arcs.

[stridsvognen]

The hole crazy idea trying something new is that i see both my Marquee have some crosstalk betwen colors, anyone try put up a 100% IRE window on green tube and look into blue and red and tell me whats going on there.

Also try look the blue and red when it writes no sync on the screen.

[Nashou66]

Kurt the static build up on the Tube is very high and the best place to remove that ground was on the VNB surge arrestors since the tube and VNB are sort of a closed system.

Now I have noticed the raster light up on all tubes when for instance onl;y showing the Green grid etc.

I have been wondering about it for some time. I used to think it was the HVPS G2 resitors. I had to use a higher resistor on one HVPS and it corrected the issue. Then I noticed it from a certain CLM I had. If i moved it from PJ to PJ the issue followed.

So I think it might be the G2 section on the CLM but not sure. It is all on one chip, a quad op amp. I am wondering if a better chip there might help.

But this is all theory.

Athanasios

[stridsvognen]

I actualy noticed changes when changing the G2 resistor in the HVPS to, so im sure it can be some sort of noise traveling true the G2 conections.

The thing is that its mostly visible on the right and left side of high level stuff. Put the green 100% IRE test window from your radiance, and i think you will see 2 vertical lines one on left and on another on right side of the window.

I cant pin it on any of my 3 different CLM.

I moved the aquadag cables back on the neck board, and im sure i liked the image better before, it was sharper and had more low level details.

[Nashou66]

[stridsvognen]