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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Sat Jun 12, 2010 9:47 am Post subject: How critical is the tape down the tube necks? |
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I only ask this cause when i replaced the tubes in a Sony recently, the new tubes did not have the tape, and i didnt put any on either.
Is it critical or is it just there so things stay still?
Also, when i siliconed the HV boots on, i used Permatex ULTRA BLACK RTV, and i only left it about 1.5 to 2 hrs before i fired it up, what is the downside to that? I read somewhere recently it should be left for no less than 24 hrs to fully cure before it is fired up.
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Sparky015
Joined: 12 May 2009
Posts: 1185
Location: Cleveland / Akron, OH
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| Posted: Sat Jun 12, 2010 12:26 pm Post subject: |
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If you have no arcs, then there are no downsides to firing your pj up early. When that stuff cures, it outgasses a bit. Possible an arc could use that gas to arc, but if your boot is good with no holes, it doesn't really matter as long as it's sat long enough to not be able to move.
The tape does nothing else but tighten the magnetics up a bit on the tube neck. Helpful when you are making adjustments and the lock rings are not screwed down yet. Other than that, the tape does nothing else. If you didn't use it, no big deal.
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~Paul
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Sat Jun 12, 2010 12:33 pm Post subject: |
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Cheers mate, i do have an arcing issue.
I havent had the chance to open it all back up and see what's what yet, but i can only point the finger at 3 items, one was the tape, and the other 2 were lack of ground wire ( which wasnt ever there to start with ) and not letting RTV cure before fire up.
Last time i fired it up, it arced like buggery.
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Sparky015
Joined: 12 May 2009
Posts: 1185
Location: Cleveland / Akron, OH
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| Posted: Sat Jun 12, 2010 12:49 pm Post subject: |
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well, your in good company, because my red tube has arcs that I'm in the process of fixing. Problem with mine is that is only arcs twice before it blows my HDM.
Mine appears to be arcing from a damaged HV boot from when I uninstalled it from the old tube. Rookie mistake in my part. You may want to check out your boot as well. It's possible yours is due to uncurred RTV, but I don't know about that. I've never done an experiment to test uncured RTV versus cured, but I would think it wouldn't conduct.
Also keep in mind that if it's a new tube, some arcs may be normal as their might be contaminates in the tube. Good luck! Hopefully your not blowing boards like me.
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~Paul
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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Sat Jun 12, 2010 12:59 pm Post subject: |
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Arcing is also caused by inadequate connection between the graphite coating on the outside of the tube bell and the grounding system.
You can get graphite paint if your tube's coating of it is worn. Use copper foil tape and stick it to the tube bell and burnish it down well
for good contact, and solder ground leads to it and ground them well.
The glass tape on tube necks is only there to help retain the magnetics snugly into position. It's helpful but not essential.
CJ
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Sat Jun 12, 2010 6:47 pm Post subject: |
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The tape isn't necessary. The manufacturers put it there to keep things from moving in shipping.
If you can hear snaps that's tube arcs outside of the tube. The internal ones have a much duller less loud sound.
One bummer about external arcs is that they are in the atmoshere which contains CO2 which is part carbon. The arc tends to produce a carbon track on whatever it is arcing across. Carbon is conductive and will soon makes things worse. Clean the surface real well where something has been arcing. If you can't get the carbon out it will never stop.
Scott
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"Were we directed from Washington when to sow and when to reap, we would soon want bread."
Thomas Jefferson
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Jun 12, 2010 9:31 pm Post subject: |
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Lets not forget that carbon can also be resistive such as a poor HV connection causing carbon buildup and the arc then travels around the carbon causing that pfizzing sound....What's that? Shut up Ron.....  Ok, I'll shut up....  Sorry.........
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Sun Jun 13, 2010 1:56 am Post subject: |
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| Sparky015 wrote: | well, your in good company, because my red tube has arcs that I'm in the process of fixing. Problem with mine is that is only arcs twice before it blows my HDM.
Mine appears to be arcing from a damaged HV boot from when I uninstalled it from the old tube. Rookie mistake in my part. You may want to check out your boot as well. It's possible yours is due to uncurred RTV, but I don't know about that. I've never done an experiment to test uncured RTV versus cured, but I would think it wouldn't conduct.
Also keep in mind that if it's a new tube, some arcs may be normal as their might be contaminates in the tube. Good luck! Hopefully your not blowing boards like me. |
Thanks mate yeah, mine will arc all day long if you leave it run, not that i have, but it is arcing to the chassis from one or 2 leads, and arcing to the green deflector yoke near the HV splitter.
5 layers of heatshrink wouldnt stop it arcing, but again, it didnt arc right from the switch on, it takes at least 20 seconds before it does.
| cmjohnson wrote: | Arcing is also caused by inadequate connection between the graphite coating on the outside of the tube bell and the grounding system.
You can get graphite paint if your tube's coating of it is worn. Use copper foil tape and stick it to the tube bell and burnish it down well
for good contact, and solder ground leads to it and ground them well.
The glass tape on tube necks is only there to help retain the magnetics snugly into position. It's helpful but not essential.
CJ |
Cheers mate, every time i do abit of reading i find another thing to add to the list for when i get this thing pulled apart, read a few tube replacing tech tips for various projectors last night and saw the tape thing in every one of them!
If this grounding of the tubes is an issue, will it still be likely to arc from the leads to the chassis or would it arc from the tube bell it's self? This is the part that has me abit confused, but i spose the HV leads do connect to the tube bell, so i guess there wouldnt be much stopping the arc from going via the leads.
I had a thought to wrap some copper wire around the tube bell and screw that to the chassis like a ground strap, would this work or is it worth a shot?
Thanks everyone for the help!! 
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Mon Jun 14, 2010 12:31 am Post subject: |
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Ok, im going to replace that silicon today and inspect the grounding, so i should know in the next couple days if itll go again 
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Mon Jun 14, 2010 10:57 am Post subject: |
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Before i got to my NEC today i pulled the tubes out of the Sony, removed the leads and removed the ULTRA BLACK, cleaned it all up as best i could, then put them back on with some clear silicone, which ill leave to cure for the rest of the week.
Fingers crossed, i hope it bloody works!!
Got minor issues with the NEC point convergence not working now....
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Sat Jun 19, 2010 8:47 am Post subject: |
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Well ive gone from 5 separate arcs from 4 different HV leads down to one minor arc from the right flyback transformer lead, right at the point where it enters the HV block. It was arcing to the green deflector yoke.
Ive coated that lead with plenty of clear silicone about 1/4 inch thick, and put some on the deflector yoke as well, and if all goes well, this Sony will be all fixed!! One would hope....
Thanks very much to all those that have helped!!
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