Tweet
My kalamazoo model 1 had been working flawlessly after I had changed out the filter caps, with no hum whatsoever for about 2 years. One day I turned it on and was met with a loud hum and no guitar signal reaching the speaker. This has stumped me for awhile now and I had put it on the back burner as I had other amps to work on with easier fixes.
As I pulled it out the other day and did a chopstick test on it, I found that the 12ax7 tab on pin 3 had broken off (amazing how much tension this was under for all those years....I could barely stretch it back in place).
So I replaced the tube socket and fired it back up but it's still not working right. Now I can hear the guitar through the speaker and with the volume on 3 the hum isn't too bad. The baffling thing is that the hum increases if I turn the volume knob up or down. At a higher volume setting it starts making this loud oscillating type hum. This seems like a grounding issue maybe but I just can't find it. Any ideas on what to look for?
As I pulled it out the other day and did a chopstick test on it, I found that the 12ax7 tab on pin 3 had broken off (amazing how much tension this was under for all those years....I could barely stretch it back in place).
So I replaced the tube socket and fired it back up but it's still not working right. Now I can hear the guitar through the speaker and with the volume on 3 the hum isn't too bad. The baffling thing is that the hum increases if I turn the volume knob up or down. At a higher volume setting it starts making this loud oscillating type hum. This seems like a grounding issue maybe but I just can't find it. Any ideas on what to look for?
Comment