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Old 15th March 2012, 04:01 PM   #1
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Default Glass bead inside of KT88

I shipped a couple of EHKT88s. The receiver of the tubes said that he can see a small glass bead, about 1mm, free moving, inside the tube. He also said that the getter was still silver and there did not appear to be loss of vacuum. The tubes are part of a kit, so he has not powered them up yet.

Has anyone else ever seen this? Could it just be from the manufacturing process? Is it a problem?

Thanks,

Scott

Last edited by scott17; 15th March 2012 at 04:11 PM.
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Old 15th March 2012, 04:26 PM   #2
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I've seen small glass extrusions from the manufacturing process brake off. In one of my rectifiers I have a 2cm piece of glass which broke off the anode connecting rod (top connection to internal plate). No harm comes to the tube but it obviously depends. Being a sphere I guess manufacturing debris and NOT piece of the tube. Hopefully it did not damage anything.
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Old 15th March 2012, 04:40 PM   #3
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Every KT88 has balls, that one moreso?
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Old 15th March 2012, 06:05 PM   #4
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Quote:
Originally Posted by cyclecamper View Post
Every KT88 has balls, that one moreso?
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Old 15th March 2012, 07:51 PM   #5
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I am the receiver of the tube

I have attached a picture where it can be seen a small piece of glass in the bottom part of the tube, I think you can figure out the real size by comparing it to the base.

Best regards!
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Old 15th March 2012, 08:53 PM   #6
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Meh,let it settle out into the bottom of the tube,It shouldn't cause any harm.
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Old 15th March 2012, 09:15 PM   #7
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Quote:
Originally Posted by regiregi22 View Post
I am the receiver of the tube

I have attached a picture where it can be seen a small piece of glass in the bottom part of the tube, I think you can figure out the real size by comparing it to the base.

Best regards!
Completely harmless, nothing to worry about. It actually happened more on old stock stuff than on the new production.
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Old 16th March 2012, 02:48 AM   #8
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I had exactly the same issue with a set of Electro Harmonix KT88's I bought a couple of years back - a small piece of glass about 2 or 3mm across inside the tube. Did not have any issues with that tube. I'm sure I could dig the tube up if you want a photo. Ironically, it was the tube WITHOUT the random glass bead out of that set that failed first....
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Old 16th March 2012, 09:41 AM   #9
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Seems ok so far, but it looks like the glass bead is small enough to fit through the holes in the anode structure - where it might cause mechanical damage to the screen grid. So better be careful when moving the tube and check/watch where the debris is.

Luckily, glass is non-conductive, so there shouldn't be any problem with it.

Greetings,
Andreas
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Old 16th March 2012, 09:43 AM   #10
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I have a CV717 that's exactly the same, never given any grief.
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