Anytime I buy an amp used, I like to go through and replace tubes with high quality new tubes (or tubes I have that I know are good). I do this to make sure the amp is running correctly and sounding as good as it can, as well as making sure it’s running stable. This week I was finally able to get a set of tubes from the Tube Amp Doctor for my Bloomfield Drive 100-watt head, so I went ahead and swapped them all out as well as bias the amp.
Afterwards I played the amp for a half hour or so enjoying the slightly lusher and more sparkly clean channel before heading to bed. The next morning, I jumped back on there and switched to the gain channel to dial in some overdrive when I was confronted with a horrible static oscillation on low notes. (Tried to capture on video but compression and framerate removes it.)
Not sure what could have gone wrong, I started going back through and replacing one tube at a time. During this process of turning the amp off, swapping a tube, turning it back on and letting it warm up, play an open E, hear issue, repeat, I noticed it was only on the Lead channel. Eventually, having gone through every single tube and still having the issue, I switched the amp to the lead channel using the toggle switch on the head. No issue.
You see, up until that day I had been using the toggle switch on the head almost exclusively to engage the lead channel, but earlier that day I decided to plug in the footswitch. It turns out something with the foot-switch is causing the issue. I was about to bite the bullet and ship the head across the country to Two-Rock to fix before I tried this, never realizing that could be an issue.
Just goes to show, try EVERYTHING when trying to fix an amp. Some of the weirdest issues can come from really unexpected places.
Support the channel by buying gear on Reverb using our Link.