rlord1974
Active member
OK, so I have had power tubes fail on me in the past, but it has always been an easily diagnosed situation. Turn amp on, play awhile, fuse blows, no more sound -> replace tubes, rebias amp and FIXED.
This afternoon, I ran into issues with two of my Marshalls: my 9200 power amp and then my 2204 head.
In both cases, I was happily playing along and they sounded great. All of a sudden there was an audible 'pop' through the speaker and then a loud "buzzy" kind of hum. It kind of sounded like if you were to pull the guitar cable out of your guitar while playing and then hold the tip of the jack plug with your fingers. You know the sound I mean? Anyways, it was a constant hum and I was unable to get any guitar signal through my amps. I could play with my guitar volume all I wanted but I could hear no guitar - just the constant hum.
I changed out all of the preamp tubes with some spares and the hum continues. I suppose it's possible it still might be a preamp tube (as the spares were older 12AX7's I had replaced in amps previously and held onto as they weren't really toast yet at the time), but the sound is not microphonic and there is no issue when I tap on the preamp tubes with the shaft of a screwdriver. As a result, I am leaning more towards (a) a power tube problem or (b) a cold solder joint somewhere in the amps. That being said, I find it unlikely it's a cold solder joint, as I hadn't used the 2204 in quite awhile (maybe a year or two) and it has been sitting in storage. I do gig occasionally with the 9200 and it had been working fine.
Finally, there is no noticeable 'lightning' in the power tubes either, and no fuses blowing, so WTF?!
Anybody have any ideas before I go out and blow $200 on new power tubes???
Thanks!
This afternoon, I ran into issues with two of my Marshalls: my 9200 power amp and then my 2204 head.
In both cases, I was happily playing along and they sounded great. All of a sudden there was an audible 'pop' through the speaker and then a loud "buzzy" kind of hum. It kind of sounded like if you were to pull the guitar cable out of your guitar while playing and then hold the tip of the jack plug with your fingers. You know the sound I mean? Anyways, it was a constant hum and I was unable to get any guitar signal through my amps. I could play with my guitar volume all I wanted but I could hear no guitar - just the constant hum.
I changed out all of the preamp tubes with some spares and the hum continues. I suppose it's possible it still might be a preamp tube (as the spares were older 12AX7's I had replaced in amps previously and held onto as they weren't really toast yet at the time), but the sound is not microphonic and there is no issue when I tap on the preamp tubes with the shaft of a screwdriver. As a result, I am leaning more towards (a) a power tube problem or (b) a cold solder joint somewhere in the amps. That being said, I find it unlikely it's a cold solder joint, as I hadn't used the 2204 in quite awhile (maybe a year or two) and it has been sitting in storage. I do gig occasionally with the 9200 and it had been working fine.
Finally, there is no noticeable 'lightning' in the power tubes either, and no fuses blowing, so WTF?!
Anybody have any ideas before I go out and blow $200 on new power tubes???
Thanks!
