Help! B-15N Rattles only on when I play a E

[plmaurer]

I just purchased a pre Magnavox (Circa 1970) B-15 N. It is the four input variety. Here is my issue: Whenever I play an E note in the bottom two octaves it makes a horrible rattle that over powers the note. This happens at moderate volumes or above. Moreover, it does not happen on any other note anywhere else on the neck. I thought it was a speaker issue so I replaced the speaker but to no avail. The new speaker sounds just the same. Any ideas?
Thanks.

 

[plmaurer]

I was wondering if it could be an issue with one of the tubes?

 

[jmercer91]

is it a physical rattle? can you stop it by touching parts of the amp that vibrate?

 

[Sherwood]

It sounds like a cabinet resonance issue, to me. It wouldn't have anything to do with the tubes.

 

[megadan]

As Sherwood mentions, it's the cabinet itself resonating. Try tightening any bolts or screws, or consider adding some stuffing to the cabinet which (IIRC) can change the resonant characteristics.

 

[plmaurer]

It crackles and rattles and does not stop when I touch it... It is only when I play an E. Very strange.

 

[JimmyM]

b-15's rattle. it can often take days to chase them all down. check every single part. check for leaks around the dolly mount and lid gasket. eventually you'll find it. also, rattles in the room can fool you into thinking they're in the cab. take it outside or to another room and listen.

 

[plmaurer]

Thanks. I will try it out.

 

[coreyfyfe]

Lid gasket is a big one. It should be sort of cushioned around the top. You can add some thin foam around the edges to help seal the cab when it's clamped down.

 

[vin*tone]

I did a whole lot of trouble shooting on mine a while back...
http://www.talkbass.com/forum/showthread.php?t=398097&highlight=rattle+hum

On mine the baffle had come loose- there were other issues as well.

 

[fretster]

There are some ornaments on the Christmas tree that rattle when I play a Bb. Tree is coming down soon though.

 

[Jim Carr]

I remember that sound very well. I have not heard it since 1968, and I never will again, I hope.

 

[Jim Carr]

I have had a microphonic 12-ax7 tube and behave this way, for what it's worth.