Glass bead inside of KT88

scott17 · 04:11 PM

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

Alexontherocks · 15th March 2012, 04:26 PM

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.

cyclecamper · 15th March 2012, 04:40 PM

Every KT88 has balls, that one moreso?

Rundmaus · 15th March 2012, 06:05 PM

Quote:

Originally Posted by cyclecamper

Every KT88 has balls, that one moreso?

regiregi22 · 15th March 2012, 07:51 PM

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!

DigitalJunkie · 15th March 2012, 08:53 PM

Meh,let it settle out into the bottom of the tube,It shouldn't cause any harm.

Jim McShane · 15th March 2012, 09:15 PM

Quote:

Originally Posted by regiregi22

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.

MellowTone · 16th March 2012, 02:48 AM

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....

Rundmaus · 16th March 2012, 09:41 AM

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

Doz · 16th March 2012, 09:43 AM

I have a CV717 that's exactly the same, never given any grief.

15th March 2012, 04:01 PM	#1
scott17 diyAudio Member Join Date: Aug 2009 Location: JFK	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.

16th March 2012, 02:48 AM	#8
MellowTone diyAudio Member Join Date: Jun 2006	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.... __________________ I Reject Your Reality And Substitute My Own - Adam Savage, Mythbuster

16th March 2012, 09:43 AM	#10
Doz diyAudio Member Join Date: Jul 2010 Location: Sat Down	I have a CV717 that's exactly the same, never given any grief. __________________ "To err is human.. to make a real balls-up requires a computer"

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15th March 2012, 04:26 PM	#2
Alexontherocks Account disabled at member's request Join Date: Jul 2009	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.

15th March 2012, 04:40 PM	#3
cyclecamper diyAudio Member Join Date: May 2010 Location: was Chicago IL, now Long Beach CA	Every KT88 has balls, that one moreso?

15th March 2012, 08:53 PM	#6
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	Meh,let it settle out into the bottom of the tube,It shouldn't cause any harm.

16th March 2012, 09:41 AM	#9
Rundmaus diyAudio Member Join Date: Aug 2005	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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