You may want to replace tube 7. You're lucky to know which one it is. I'd get a new set plus one extra tube that matches. Antique Electronic Supply in AZ can probably match the numbers you have now. 480-820-5411 also check your fuses and find out if any are blown. Do the tubes bias individually or all at once? I'd also call Audio Research to make sure the bias is set to their specs. Hang in there, it will be worth the effort for tube sound. Good luck.
tube amp help
I recently purchased my first tube amp- a used Audio Research VS 110 with new matched SED winged C 6550Cs put in by the seller. They were biased at 55mV per his recommendations. I've been listening for 1 week- it sounded great until today. When listening there was a brief pop sound and a quick spark from tube 7. I turned it off, waited a couple hours...turned it back on, they all glowed orange, I checked the bias. tube 7 had 0 mV, all others 53-55. Is the tube blown? Do I need just need to reset the bias? If I need to replace the tube do I need to replace a pair?? Any help would be appreciated - I am a tube amp newbie.