I have a 1976 Fender Twin that has been a good reliable amp since I was 17 (I'm a little older now). It was just re-tubed about 9 months ago (only power tubes) and it has been working fine until the past couple nights. The sound changes like I turned the tone knob on the guitar to "0". Stays like that for a minute, gives a slight audible crack, and returns to its nice crisp, clear tone for about a minute and the the cycle repeats. It seems to stop after about an hour of playing. I usually give the tubes 10-15 minutes to warm up. I play thru a GNX3 pedal board. This happens on multiple guitars and cables. In my limited electronics knowledge, I was wondering if the filter caps may need replaced. I have been keeping the amp in my garage but the weather has been nice lately, no rain, little humidity but it still gets cold at night. Any help would be appreciated.
Last edited by SWilson at Apr 14, 2012,
the tube connection might be loose? if you care about your twin the way that I do try to call up a tech and see if they can look at it, i have one on speed dial and the second something starts sounding off i call him up, i love that amp and will do whatever it takes to keep it going.

that being said I'm not a tech at all so I can never estimate what the problem is myself, there are some guys here on UG that could probably help you out more than me
Fender Strat Deluxe
Fender MexiStrat
Epiphone Sheritan
Ibanez Artcore
Fender Twin Reverb silverface
Roland JC120

Quote by CaptainAmerican
I would recommend the marshal MG100

Very versatile and quality sound. It should treat you well