Problem with Ref 5SE

Good luck on the power tube. Also when you change the tube take a look at the board around the tube socket and see if it shows any sign of overheating or burning. Pull the bottom grate as well and look the bottom of the circuit board over as well. As mentioned, mine had burned from the tube being into long, I bought a demo and the dealer didn’t realize it was past it’s life expectancy. He was cool and paid freight. But if it shows a sign of overheating send pictures to ARC so they can further diagnose if the 6550 doesn’t solve the issue.
But I hope it is just the tube. Let us know how it pans out.
One last note, mine is dead quiet as well unless at full volume with no source. But really when would ever happen

+1 on staying with stock power cable...it bested everything else I tried.

It certainly does sound like a power supply issue, which could include the 6550 tube.  The advice to look for burned components (check for tell tale odors too) is good advice.  Even if such overheating of a component is not related to your problem, it is good to know if there is other trouble brewing in the future.  I hope it is the 6550 tube because that is an easy fix.  

I purchased a new 5 se four years ago and just recently have had a similar problem. The first thing that happened was the static noise. It came out of both channels. Then I started getting a loud pop out of the speakers, and the amp. would go into dc offset and shut off. After about 20 seconds the amp. reset and came back on. After a few minutes the pop happened again. This time the amp reset but the system would not come back on. I called my ARC dealer . He is a 30 year veteran ARC dealer. He said to bring the pre amp into his store. After taking the cover off the 5 se we discovered a burn mark about the size quarter. directly over the 6550 tube. He took the tube out and it was black inside the tube.  He had a used 6550 and installed it. The pre amp came back on but the static was still there. he put his thumb and index finger on each of the 6h30p tubes and rotated each one gently. When he did each tube gave out a loud static scratching sound through the speakers. He seemed to think there may be oxidation on tube pins or on the sockets. This pre amp was purchased new and had the original tubes still in it. The tubes had almost 4000 hours on them so we ordered a brand new set from ARC. we replaced all of the tubes as recommended. We got the same static problem. We took all the tubes back out and cleaned the tube sockets with de ox and a tiny wire brush. After putting the new tubs back in the static stopped and the pre amp sounded like new. After a short break in time my system was back to normal. While at the dealer I checked the cover of his 5 se demo model and the clear lucite cover had a burn mark directly over the 6550 tube just like mine.
 We also checked his Ref. 6 demo and it had the same thing. After talking to ARC and the dealer I find out that some people run their ref 5 and ref 6 amps with the covers off because of the heat from the tubes. One veteran repair man I know said the sockets of an amp this new should not have oxidized this soon. He also said the oxidation may have been caused by the excessive heat .
 I am worried about what will happen in the future when it comes time to install new tubes. I think that changing the 6550 tube after only 2000 hours is wise, only because it runs so hot. 
I hope this sheds some light on this subject. I would love to hear from other ref 5 and ref 6 owners and see if they have burn marks or melting marks over their 6550 tubes. Has anyone had a similar problem with the static, or the 6550 tube burning out? Thanks for all your help.

What would Roger have done?