Rattling power tubes

[Leevi]

I know this topic has been handled several times here.


I have a problem now in a 5E3 I built recently. JJ 6V6s are rattling with certain notes.


In my case it's very difficult to analyze if the rattling is mechanical vibration or is it caused
by microphonic tubes?


I know that there are silicon tube dampers but are there any other ways to prevent/minimize
rattling?


/Leevi

[tubenit]

In my case it's very difficult to analyze if the rattling is mechanical vibration or is it caused
by microphonic tubes?

Those two concerns are usually inter-related.   Remove the chassis some short distance from cabinet and play thru the amp that way. How much of a problem is there then?

Silicon tube dampers do work somewhat.  Creating a head and cab separate also.  Sometimes making a socket isolated with a silicon washer from chassis helps.  Sometimes a bear claw clamp can help, but then I've seen that be a contributing factor also.

With respect, Tubenit

[Leevi]

Remove the chassis some short distance from cabinet

I have done this. With shorter distance the problem is there still but with 2-3 meters distance
the situation is remarkable better. I'm thinking that it's microphonic since the rattling occurs
even if the chassis has been taken out of the cabinet.


/Leevi

[tubeswell]

I use adhesive door weather seal strip rubbery stuff between the chassis and cab contact surfaces, and in fact between the baffle and the cab contact surfaces, and between the back-panel and cab contact surfaces and (for tweed type amps) between the back panel and chassis contact surfaces. This deadens any vibration being transmitted into the chassis from the cab, and works for me. In short, wherever you can deaden mechanical vibration, you will increase tube resilience.

[Leevi]

This deadens any vibration being transmitted into the chassis from the cab, and works for me

This might help. I have noticed that when I touch the tube during the rattling the
rattling stops immediately. So it has something to do with vibration but a good question is
if there is even an electrical factor causing it, like microphonic or oscillation?


/Leevi

[AZJimC]

If touching the tube stops the noise, then I'd say the tube is bad, or the touch is causing better contact on a loose pin. Try re-tentioning the pins, and check the solder connections, and then if the noise is still there, swap the tube. I think if you had an internal part become microphonic, touching the tube would likely have little effect.

[Leevi]

then I'd say the tube is bad

You are right. I changed one the power tubes and the situation improved a lot.


Hopefully the root cause was the tube.


Thanks
Leevi

[tompagan123]

I've had some quality issues with JJ 6v6S lately.  I've heard of other reports of quality with the factory in Slovakia.  I've also had a similar internal rattling problem with a Tungsol 5881 reissue.  Really nice sounding tubes.  Better than the JJ 6v6s. I don't know if this was a fluke or not.  I finally settled on Electro Harmonix 6v6.  I'm losing a watt or two in output power but they sound great clean and overdriven and *seem* to be reliable.  Time will tell.   

[jeff]

I recently had a similar problem. Certian notes would sound awful but sound good when I held the tube still. I tried to retention the pins and nothing, so I replaced the socket and it solved the problem.

"Improved alot" or fixed? Have your tubes been in and out and in and out alot? If the new tubes fixed the problem, great. But if it shows up again try retensioning or replacing sockets, worked for me.