Mesa Clean channel started humming

T

tom18222

yes
Hey,

I have a mesa boogie dual recto. Recently my clean channel started to hum and when i turn the amp up loud it feeds back wicked. I assume i have a bad tube, right? I used to post here every day for years, now adulthood has totally taken over my life and I totally forget about how to diagnose these things. Do i need to replace every tube? Do i have to bias the amp or something?

Thanks

Tom
 
Mesa's don't have bias adjustments, so no need to worry about that. To test for a microphonic tube, remove any tube covers, and with nothing plugged into the amp, turn it on and allow it to warm up. Take the amp out of standby and turn up the volume. Using a pencil or light wooden dowel, gently tap each tube, starting with the pre amp tubes. If you can hear the tap being amplified through the speaker, then the tube is microphonic and needs to be replaced.
 
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