12AX7

My bass amp stopped working. I was going to bring it to CCCSB since I'm not playing anywhere but when I turned it on last night, there was no signal. I checked the amplifier section by plugging my iPod into the Effects In jack and got some sound, which means the bass preamp section is bad. Like any good engineer, I took the cover off the amp, even though I don't know how to diagnose it anyway. I just wanted to see if there was anything obvious, like remnants of an explosion or fire or something...


Internals of the SWR 350x bass amp. Most of the circuitry was for the preamp section (left). The actual amplifier section (right) was working.


The only user replaceable part is the 12AX7 vacuum tube. When I bought the amp used, the guy selling it to me said he just replaced it. The manual said it needs replacement anywhere between one to three years so I guess it's time. I went online and was surprised to find very few electronic component retailers left, and most are from the 50's and 60's. I guess nobody fixes stuff anymore. I ended up ordering two tubes from an online retailer so hopefully I can just replace the tube and get it working again.