Best way to cure preamp tube rattle?

[leydenjar]

I have an AB763 Super Reverb with a rattle coming from V2 that I need to eliminate.

Holding the tube firmly works but the old tube shield doesn't do anything except make it worse.

Recommendations?

[Jazz P Bass]

Does changing out the tube help?
If it does not, that begs the question of what is rattling.
I have noticed some preamp tubes where the bottom of the glass is not flat.
Is that the rattle? Tube to socket interface.
Try lifting the tube up (down in this case) a little & see if that helps.
Another thing is the pin & socket connections.
Are the pins straight?
Did you try 'retensioning' the socket tabs?

[Chuck H]

+1
Usually a rattling tube is either a mechanical problem with the tube itself or a loose/dirty pin connection. Sans that, I've has pretty good luck putting a pad of rubber, heat resistant gasket material between the tube and socket. But I've only done this make shift shock mount with EL84 power tubes in an amp that would blow them out microphonic in about sixty hours otherwise. Never found a need to do it with preamp tubes.

EDIT: I should also metion that rattle problems that can be traced to a specific tube may also be cold solder joints associated with that tubes circuitry.

[clyde1]

I've use heat-shrink tubing with good results. You can size and position it so that the shield can still be used.

[pdf64]

When I've raised this problem, various types of vibration dampening O Rings (fitted over the tubes) have been recomended (need to be used without the tube shield).
I didn't end up trying them out, rather I put the amp chassis into a head cab, I decided that I've had it with combos.
Pete

[leydenjar]

Thanks for the replies.

I'm attaching a photo of an odd solution I'm only aware of because one of my collection of tube shields has it stuffed inside. The "it" in this case is some kind of foam. It seems to work nicely.

Has anyone ever seen foam implemented in this fashion?

[oc disorder]

Has anyone ever seen foam implemented in this fashion?

No I haven't seen that exactly but as long as the foam doesn't melt it should help providing it's firm.

Mesa Boogie had a bracket that contains foam which when screwed down pushes firmly on the tubes.
Peavey also use foam in the 5150 and more recently have implemented it in the classic 30 on the output tubes !

Although I haven't tried it I have been impressed with German engineering in the old "goldish" looking Klemt Echolette.
On the most sensitive tubes the sockets are shock mounted, rubber grommets on the mounting holes.
Somewhere on the forum another Aussie is selling one not working but perhaps thats going a little too far !

Saw this
Weber Chassis Products

9 Pin Shock Mount (Tube socket and shield not included)
Shock mount device for preamp tubes to help prevent chassis-induced vibration noises.
May also be used for 9 pin output tubes.
Includes shock plate, grommets, springs, and #4 mounting hardware.
9 pin socket ID is 3/4", mounting ear holes center to center is 1-1/8".

Otherwise I think finding a non microphonic tube for that position is the way to go.

[Chuck H]

+1
Any shock absorning material will help. But it's much better to stop the shock from getting to the tube than to try and remove it once it's there. That's why I mentioned the rubber gasket thing. I used heat resistant gasket material because I had it on hand. But a silicone pad should work even better. Short of replacing the tube socket with a shock mountable one or shock mounting the one you have if it's possible, a small pad between the tube and socket should help a lot. If the pad isn't too thick you could still use your foam topped tube cover for added benefit. I've read here about builds where guys take it all the way with shock mounted chassis AND tube sockets AND retainers. It would seem your not alone in your quest.