What happens if my tubes rattle when shaken+how to test tube

[sir_modulus]

I found that 1 out of 4 tubes I bought rattles when shaken. They all check out okay with a ohmmeter (6V6's) heaters have decent ohm reading, nothing else is connected. if i can hear stuff, does this mean the tubes are bad? What is a good way to test them (without tube tester).

All help appreciated, need fast replies.

thnx

[cd]

Put them in an amp and see if it's microphonic.

[Lonestarjohnny]

my experience with all the old tube's i have is that sometime's from being shiiped a long way's the tube's that have large plate's may stand a chance of getting the plate loosened, and this can lead to the tube shorting out, if you have the cathode protected with a 1n4007 diode on the amp you try these in you can run these tube's, and if they short out you loose nuthin but the diode, if your amp is unprotected in this manner a shorted tube can take out a transformer before the ac fuse can pop and then you got bad problem's so be careful useing them if they rattle when you shake them.
JD

[Dave Z]

Not a good sign...might be worth investing in a couple of JJ or EH 6V6s, about $7 ea if you hunt around.

RE short protection, I'm pretty paranoid & I put short protection across my screens, AND a fuse on both sides of the tranny...if you want to see details I have the schem of my AX84 "Cal Dreamer" in my Yahoo briefcase:

http://briefcase.yahoo.com/fenderelectric
See "Cal Dramer Amp" folder

also on AX84:
http://www.ax84.com/california.html

Note the 1K 3W resistors on the screens, and the 250 mA FastBlo after the rectifier...the 3W resistors are enough to keep the tranny from blowing up long enough for the fuse to go, but WILL burn up, providing a visual clue to the failure...if you want screens that won't die, use 5W or better, but those are kinda large!

[petemoore]

Yupp, might get a funky sound...I've seen/heard some ragged looking/sounding tubes.
 They can get to actin' 'lil' 'funny'. This can be a ragged sound, or in the case of high gain amping with treble use cause even for speaker failure, if really 'wierd' [more intense than usual] high end screeching starts coming out, stop playing and attenuate the volume or trebel immediately, then get another tube in there.
...The Old Boogie tubes [very old] got wild with the high end and blew out 1.5+ Fane 10'' speakers, out of 4 x 10'' Laney Cabinet...he started to use the microphonics for harmonic feedback 'accentuation' at high level for a few seconds [I tried screaming about Sp Damage, but..]
 That thing has 12 Tubes in it [IIRC], that's one reason I picked one out that has 5.