CurtPalme.com Home Theater Forum

[comm]

Hey guys,

Well, I am back to working on the Marquee after over a year. Due to moving, work, and now trying to finish the theater I have not had a chance to touch it. Guess I need to get my priorities straight.

I had the nice edge-a-sketch like spot burn on the blue tube.
https://www.curtpalme.com/forum_archived/viewtopic.php@t=11051.html

So here is where I am at: I can now turn on the projector and it does not spot burn the tube like it did the first two times.

Well at least I don't think it does. I have noticed now that there is more burn on the tube that I originally thought, it was just too light to see without the tube powered on. Horizontally across the tube face there is a light ellipse drawn and below the horizontal line a vertical ellipse. I drew what it looks like on a crappy paint diagram since I don't know if I can get a picture of it.

I am guessing it was one of three things?

1. Contamination. This is what Curt suggested. I turned to tube on its face and tapped on the neck and have not had a problem since I did that.

2. I don't know how well my ground strap is working, I can hear some very quiet static discharge when it is running. Just a small tick every second or so. I do not see any arcs with the lights off. Maybe it arced to the deflection yoke and caused burn? Since I moved the tube around to tap on it not sure a wire it was arcing from got shifted.

3. I might not have waited long enough for the silicon to dry and it arced from the HV boot?

I am hesitant to put another tube in until I have a better idea of what caused it. Any suggestions?

[Nashou66]

The ticking could be the boot since you did not let it dry fully, at least a week before turning on. Now there might be a small path for the HV to travel through, more silicon and a week of curing will stop it, if that is where the tick is coming from.

I would remove the plastic covers from the blue tube and run the PJ in the dark to try to se if the arc is visible anywhere along the entire tube.

And I agree do not put another tube till you find out what caused the strange spot burn.


Others might have more to add.

Athanasios

[comm]

Thanks for the reply Athanasios.

I have removed the cover for the tube and looked for arcing in a dark room and have not been able to see any. I have noticed the ticking sound seem to get worse the longer the projector has been running.

I can't remember how long I let the silicon dry. It was either two days or a full week, it has been too long now.

I am trying to get a picture of the other burn on the tube.

David

[comm]

Ok, I took a picture of the burn through the lens. I lightened the image to make it more visible, very hard to see without the tube lit.

I noticed that the burn does not extend past where the rastor was set before I reset the geometry.

Is a stray arc something that could cause this or something else altogether?

David

[draganm]

I've never seen anything like that before. It looks like contamination was picked up by the electron beam and and slammed into the Phosphor, sept that doesn't make sense?

[Nashou66]

Looks like the Phosphor is delaminating from the glass. I have heard of it but never seen it.

Unless the Spotkill circuit went south and where the voltage should shut off during beam collapse it did not, all happening together with a Horizontal and vertical scan fault. Ummm make sense? Possible? I do not know for sure but maybe...

Nashou

[comm]

I am sure its been burned onto the phosphor. It's hard to see in the picture but there are some wicked patterns in the burn; kind of looks like a picture of a Tesla coil.

What's gets me is that after all this damage it just stopped and I didn't really do anything. Just tapped on the neck and moved some cables around. Or at least I think it stopped, it would be hard to notice if it was still burning in that same pattern. At very least the two times it spot burned the upper left corner have quit.

David

[stefuel]

Take your pictures with the lenses off. Less distortion that way.

[comm]

Here are a few better pictures.

While taking these, I spent quite a while trying to trace that ticking sound down and finally saw an arc. There is a small arc coming from the shrink wrap on the HV boot to the front plastic edge of the deflection yoke. I have looked for an arc before in the dark times and never found anything because it seems to only arc visibly 3 or 4 minutes.

So I am guessing that is my problem...

David

[draganm]

[comm]

Yep, I have the old style boot. I'll try filling it with silicon and see if that fixes the arcing.

I think I am going to set up the projector and see how bad the blue looks on screen, but I am guessing that I will probably have to start the search for a new blue tube.

David

[comm]

Well, thanks for the help everyone.

I have put silicon on the boot and in the heat shrink sleeve and still had arcing. So I went ahead and removed the boot, reattached it to the tube, and globbed silicon all over the outside. I let it cure for a week and still had arcing. Found the leak in a dark room, patched where I could see the arc coming from and let it cure again. Still have arcing!

So unless I am using the wrong silicon (GE Silicon II) I think it is time for a new hv boot. Anyone know where I can get one? Maybe I should just try to find a tube with one already attached since I feel like I have found the source of the problem...

David

[CZ Eddie]

I dunno how to help with the arcing.

But I have to say that you have some serious streaking going on! Might be time to swap some boards out or check out the marquee maintenece thread to replace caps/resistors.

[Sparky015]

GE Silcone II works. I believe it's what most people here use, at least in North America. Arcing from the same spot after you patch, or different spots? Did you clean all of that dust off with Isopropl Alcohol? That dust is conductive and makes arcing worse.

[draganm]

[Nashou66]

I would not bother wasting time on a new boot for a shot tube that might have the Deflection coil fried from the Arcing of the HV boot.

Look for a different tube with all magnetics on it first. Ask Curt if he has a tube that is shot, doesn't have to be blue just one that is fried for 10 bucks or so, so you can use it for testing incase its not the arc that caused the strange spot burns on that blue tube.

Then if all is well and no more strange burns or arcing I'd go ahead and find a nicer Blue Tube.


Athanasios

[Curt Palme]

Due to being out of town, I've been a bit lax in following up on some emails and posts, so I emailed the below, and thought I'd post it here as well...

1) Any burn mark on a tube face outside of say the center 20% of the tube is almost always related to a fault in the tube. At least that's what I've seen from all the tube burns I've had here. Your burn is very light and squiggly, which I am guessing is contamination within the tube.

2) I have never seen external arcing on a tube cause a burn on the tube face. Arcing almost always damages a deflection board (H or V), but doesn't damage the tube itself. Regardless, I would change the Hv lead. Someone in Australia recently had tube arcing issues (of the HV lead) and it turned out to be the silicone he was using.

3) I am out of new Hv lead assemblies, but apparently I have a new source for them, I will call them tomorrow. Figure on $20-25 for a new lead, boot and HV connector that fits into the splitter.

4) I would run the set with the existing bad blue tube for 100-200 hours on and off to see if the wear/burn gets worse. If so, we need to make sure what the problem is before changing the tube. All deflection and almost all voltages/signals going to the tube are common to all three tubes, so again, since you only have issues with the blue, that again makes me think that it's a tube issue that you have. Getting a new or good used blue tube isn't a problem, but you'll need to reinstall the tube into your housing. (or I can do it here, but need your old tube first, as finding Marquee LC housings is difficult.

5) Trashed tubes, LUG or otherwise- got lots of those. I also have lots of good used yokes if you just want to change it to be sure. $20 for a tested working yoke assembly.

[Curt Palme]

Due to being out of town, I've been a bit lax in following up on some emails and posts, so I emailed the below, and thought I'd post it here as well...

1) Any burn mark on a tube face outside of say the center 20% of the tube is almost always related to a fault in the tube. At least that's what I've seen from all the tube burns I've had here. Your burn is very light and squiggly, which I am guessing is contamination within the tube.

2) I have never seen external arcing on a tube cause a burn on the tube face. Arcing almost always damages a deflection board (H or V), but doesn't damage the tube itself. Regardless, I would change the Hv lead. Someone in Australia recently had tube arcing issues (of the HV lead) and it turned out to be the silicone he was using.

3) I am out of new Hv lead assemblies, but apparently I have a new source for them, I will call them tomorrow. Figure on $20-25 for a new lead, boot and HV connector that fits into the splitter.

4) I would run the set with the existing bad blue tube for 100-200 hours on and off to see if the wear/burn gets worse. If so, we need to make sure what the problem is before changing the tube. All deflection and almost all voltages/signals going to the tube are common to all three tubes, so again, since you only have issues with the blue, that again makes me think that it's a tube issue that you have. Getting a new or good used blue tube isn't a problem, but you'll need to reinstall the tube into your housing. (or I can do it here, but need your old tube first, as finding Marquee LC housings is difficult.

5) Trashed tubes, LUG or otherwise- got lots of those. I also have lots of good used yokes if you just want to change it to be sure. $20 for a tested working yoke assembly.