5150 makes ringing/pinging noise

[patsplat]

My 5150 has went to making a ringing/pinging type noise through the speakers if I tap on the case.This is with the guitar volume down.I can also hear my voice when talking/yelling into the back of the head,especially right above where the preamp tubes are.

I was having a feedback problem and found this when trying to track it down.I have changed many of the tubes around,both power and pre,but so far the problem continues.If it doesn't turn out to be a tube,any other ideas on what may be going on?

I found this when doing a search for microphonic power tubes...

A BIG time YES, an OPT can go micro.<snip>

 

[tituba]

microphonic tube in the pre amp. try v-1 1st.

 

[BURNTHISCORPSE]

+1 on the microphonic tube

 

[Red]

take a pencil and tap each tube with the eraser end, you should be able to find it easily

 

[Buckeyedog]

+3

 

[patsplat]

Yep....bad V1 tube...I tapped it with a pencil eraser and it made a big ringy "PLONG" sound....it was a fairly new tube too

The feedback problem is gone and now the only sound I hear is just a slight tapping on a light bulb type sound.I went ahead and replaced all the pre tubes as well.

I'm off to band practice...thanks for all the replies!