Arc Ref 5se owners

In a word YES. 

This sounds like the 6550 tube. That should be changed after 2,000 hours. It should never cause enough heat to warp the top plate. I would immediately stop using it. I would go to Upscale audio and order a complete compliment of tubes. The 6H30 should have a life of 4,000 hours but since you don’t know where it has been... change them. The best place to get the tubes are Audio Research Corp. They are fully tested and broken in. But they cost more. 

If the tube is running hot after changing... then send it in to Audio Research for repair. You have a world class preamp there it is definitely worth making sure it is operating at peak performance. They can replace the cover as well. 

I owned a ARC Reference 5SE for many years, now I have a Ref 6SE. They are both incredibly good preamps. 

I agree with ghdprentice about the quality of the ARC Reference amps, and replacing the tubes, and purchasing from Upscale.

When I had the 5SE, the poly cover warped over time. I called ARC, and they explained that they used them because they reduced vibration, and that the warping wasn’t unusual. They kindly sent me a replacement, which over time did not warp. Later models used the reengineered poly covers.

I'm thinking your Ref 5SE has the original poly cover.

Appreciate the tips. 

My unit does have the thinner cover. In a post here, a member mused about the different and thicker cover on the ref 6.

To me the units look similar enough I would look into getting a replacement. However, I don't mind leaving the cover off either. 

Interesting that some of the other tube pre have metal covers? 

@ghdprentice based on your experience, a hot running tube indicates near end of life. In that case I will buy a fresh set. Everything seems to work fine. 

Thank you sirs. 

I owned a REF5SE that was a dealer demo. It also had the lexan cover which was also warped. That 6550 does generate a lot of heat. It also burned the board, which Audio Research replaced as a warranty repair. The manual does not indicate that tube should be replaced at 2500 hours, it only states replace tubes at 4000 hours which refers to the 6H30. The REF6 manual does mention the 6550 replacement at 2500 hours which helped me get the warranty replacement of the board. So not knowing when the tubes were actually replaced, I strongly recommend replacing at least the 6550 as soon as possible. Also I did order a metal cover and did away with the lexan cover. They say it sounds better with the lexan than the metal, but if that’s your motive, just don’t use a cover if environmentally possible. 
And not to start a range war, I would only buy tubes from Audio Research. I asked them about a dealer that claims to be AR approved and was told they were not aware of that claim. You may call AR and ask them, as you may get a different answer. And hopefully you can still get a metal cover, and place the unit where it has plenty of room to connect the heat away from that tube. I also have an infrared thermometer and was getting well into the 200 degree range. 
One last note, it is a great sounding pre amp, enjoy!