A Tube That Rattles

[tablebeast]

I temporarily am without my tube tester while it is being borrowed but I just get a lot of tubes in the mail that were supposed to test great but some of them rattle. As in if you gently move them from side to side they rattle like something inside is loose. I don't see anything loose in there, but it sure sounds like it. I don't want to put them in the amp if its goign to be disasterous as I fear an internal short. Should I even bother testing these rattles or are they obviously trash?

Jesse

 

[NewYorkDave]

Are the envelopes milky white? Perhaps they were damaged in shipment.

Rattling in the way you describe is not normal. Don't plug them into your amp without testing them first--or just toss 'em.

 

[Guest]

Sometimes rattle is caused by loosen compound particles inside of a tube base.

 

[CJ]

I have some old 6L6's that rattle like a mofo.
Sound great. Nothing to worry about.
Plug them in.
If your paranoid, just stand back with the line cord in your hand, or lower the fuse a bit.
The big power tubes always rattle.
You did not say what tubes, I bet they are powr tubes.
Loose octal bases are always common. Heat, vibration, Hendrix... :razz:

 

[NewYorkDave]

I guess the question is, are you feeling lucky? :razz:

Most of us are a little more cautious than CJ.

The big power tubes always rattle.

That's news to me. I've used tons of 6L6s, EL34s, 6550s and I don't remember any of them rattling right out of the box.

 

[CJ]

Dave is probably right, I never know who I am talkin to on this forum, could be a 10 kid DIY'er, could be a vet EE, so better to error on the safe side.

The worst case of loose elements I have ever seen was during a trip I made to the office of Vacuum Tube Valley. Eric Barbour and Charles Kittleson were testing this huge 4 pin SE bottle, a new prototype Sevetlana.
It was shock mounted and had a weird yellow glow instead of the normal red heater and blue plate ions. Eric said "Watch this" and barley tapped the tube with his finger. The plate, grid and cathode all started bouncing around like a sleleton on a hot tin roof.
Each element was going in a different direction, barley missing each other!
If you hit it too hard, ZAP!
Thats it for the tube.

These SE guys are sometmes weird.

 

[peterc]

I've a few tubes before that had a loose base. Put some glue down into the gap, all worked fine.

Peter

 

[tablebeast]

The tubes in question are: one 6SC7GT (Its labeled International Servicemaster which already has me worried, aren't they the guys who've sold a lot of counterfeit tubes?), two 6SN7GTs and one 5Y3GT. They all rattle pretty good without much shaking. When I turn them upside down you can hear loose stuff falling, but like I said before nothing is visibly moving around in there. I figured even best-case-scenario these are going to be noisy and microphonic as all hell. None are milky white like they would be if the tube was cracked or letting in air somehow. I'm just spooked to put them into gear and hurting the gear. I've been building a lot of guitar amps lately and one friend that I'm modifying a Knight PA amp for insists on glass for his tubes, so its been a chore finding good GLASS 6SC7's (6SC7GT) for a decent price. There are plenty of metal ones to be had, but that won't work for this guy.
Oh, and just so you know who you are talking to... I am certainly no EE, but I'm not a total newbie either. I'm probably younger than most of you guys at 28, but I'm learning quickly. I've been poking around tubes and amps for years but only really got serious about it in the last year or so. Its tough because the stuff I want to learn about isn't taught in schools any more. Lately I've been spending all my time studying and designing by myself so my knowledge is building nicely. This board has been an infinite source of wisdom, thanks so much for all your time and help.

Jesse

 

[CJ]

OK, you can plug in the 6SC7 and SN7 and there should be no major drama.
There should be a big enough plate resistor that meltdown current will not be possible. So plug them in, one at a time.
The 5y3 is a different story, but they are so cheap and plentiful.

The worst case of stuff in a tube was the story I told too much about the 300B Chinese tube with the ciggy butt inside.
I have seen broken chips of glass in tubes, and varous pieces of the cathode and heater, so nothing new. SHould not have anything to do with noise or microphonics.

 

[walter]

Use a current limiter to first test the tubes for shorts. Some rattly tubes make rattly noise, some don't. I have seen some rattly tubes that work fine, but I don't trust loose tubes. I set up an SVT with tubes that didn't rattle, and I watched one tube produce a lattice hole in the glass as a beam of radiation? melted the glass. I turned the amp off, and it worked fine with another tube. Tubes are NOT consistent.