cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Sat Oct 22, 2016 3:02 am Post subject: OLD Marquee LC assembly glycol leak |
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Something to watch out for if you have any old (say 10 years old or more) Marquee LC assemblies.
I had an older assembly sitting on my shelf, with a worn tube, that I hadn't gotten around to taking apart and
pulling the tube out. It's just not that important to me to do that given that I have maybe sixty sets of LC hardware
if I need to pot up a tube.
But I moved the tube as I was trying to reorganize to get some space back, and found a small puddle of glycol under it.
I know that tube hadn't leaked before. It was bone dry outside when I pulled it from the projector several months ago.
The tube is in storage in a NON-air conditioned storage unit. That might be important.
So I investigate this leaker and discover, to my surprise, that the leak is coming from between the tube glass
and the silicone potting!
The potting is clearly a factory Electrohome or early VDC job, perfectly done, smooth, clean, and shiny, with that
distinctive dark grey silicone that Electrohome used.
That silicone is something I like to find if I do have to yank a tube out because it's easy to pry it out in big chunks,
far faster than the time it takes to cut any other kind of silicone out. This silicone is hard, not very flexible, and has
a friable character to it. You break it up rather than cut it up.
Well, to make a longish story short, the potting had failed around the tube and you could actually move the tube
around a little in the potting while it was still fully potted. I didn't have to break out much of the potting to get the
tube out, and when I did, the tube came out with NO potting compound still adhered to the sides.
If it happened once, it could happen again. So watch for that if you have a mystery leaker.
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