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jcm800 50w - no mid or bass?

3/28/2003 2:16 AM
jcm800 50w - no mid or bass?
a couple days ago during a routine practice session my jcm800 50w (2204) got remarkably quieter and more "trebley" being somewhat ignorant i thought, i blew some power tubes. i bought new tubes threw 'em still all treble, no power... hmm... i fiddled with the knbs and when i turn the bass knob all the way up or all the way down nothing happesn no increase in volume or decrease same with the mid knob, however the treble knob when turned all the way up the amp gets much louder and when turned all the way down gets very soft.  
i also though maybe it's the cabinet. (which is a 4x12 mesa with vintage 30's) so i took the back of the cabinet off; listened and it seems that only the top two speakers were putting any sound out. ok, but just to make sure i plugged in my other amp in to the cabinet (a 50w bassman) and to my surprise all four speakers were putting out everything just fine.  
what could it be? is it a simple output jack problem? is it a loose wire? is it something simple, i'm hoping i can fix it myself  
thanks for your help.  
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