Mesa 50/50 "Resonating" type noise

[HRGplayer]

Hello there. I run a a mesa 50/50 in my rack set up, amplifying a POD HD. Since i've had it, about 6 months, occasionally it will start outputting a resonating type low note sound that seems to be coming from some combination of the fan and power tubes. Its almost like low pitched, quiet feedback. When playing louder than bedroom volume it's not a problem - at gigs for instance, never notice it. When I hold the top and bottom case plates and squeeze a bit the noise stops - when i let go it's back, so something is vibrating causing this - the noise comes from the speakers. I've rigged up electric tape to squeeze the top and bottom case plates together behind the power tubes, and this prevents the noise. I've made sure the case is all screwed together tight. I can also stop the noise temporarily by slightly pushing in or "reseating" the power tubes. The tubes i believe are fairly old, and i've ordered a new set of JJs - just the power tubes.

Do you think this mainly a tube issue or perhaps the fan is causing vibration issues? Anyone else had this issue?
Thanks in advance!

 

[a2dconverter]

Hey HRGplayer,

The sound that you are hearing is the Power transformer vibrating the top lid....

My 50/50 is a later version, (choke mounted to bottom of chassis), and there is a small piece of 3M dual-lock on the transformer and lid to damp that vibration.... you could use a piece of foam tape.

If you are looking at the inside of your 50/50 and it looks different to mine... mine has a bias mod installed...

I hope this helps you out

seeya

Joe

 

[HRGplayer]

Joe - THANKS!! Your fix looks to be exactly the solution to the noise.

Once i get the tubes in the mail and retube i'll unscrew the top and add some velco tape (fuzzy side) in the same spot. For a minute i was wondering if i was sold an amp missing the back panel, but apparently not. Thanks again!!

 

[HRGplayer]

Put in new Jjs and added fuzzy velcro tape to the top of the three transformers. Amp is like new now. Thanks Again

When i changed the power tubes i noticed the preamp tubes were ancient, have three on the way now too.