New McIntosh MA252

I remember reading in the MA252 manual about giving the speaker terminal nut an extra quarter turn after snugging it up but I didn't want to force it, so I left it like that. If I were in your shoes and it bothered me that much, I'd contact McIntosh to see if they've dealt with this before. The only issue I would wonder about is if the terminal needs to be tightly bonded to the chassis for grounding purposes.

Thanks for the input route-66.  I contacted McIntosh and they directed me to a local technician.  I was going to call him but decided to take a peek under the hood.  It was simple.  The nut that should have been "squishing" the lock washer, was almost at the end of the bolt.  Probably another rotation and a half and the nut would have fallen off.  So a 9mm ratchet did the trick.  All is good.

I was going to suggest that you pop the top off yourself but I didn't know if you'd be comfortable doing that. I'm glad that you were able to take care of it yourself and won't be losing sleep over it tonight. :-D

I tried it with Focal Kanta 2's.  It's all solid state sound.  Even the dealer said he thinks they just put the tubes in there for looks.

This 252 is a marvel - loved every bit of it. 
Changed my brystons to all Mc with no regrets. My current setup is MB50, D150 and MA252. Its jaw dropping. Drives my power hungry VA Strauss tower speakers at 90% on 14X21 listening room - without a hiccup, just pure musicality being portrayed. It sounded a real orchestra, like my sons orchestra in HS. The D150 serves as a DAC and made a huge improvement - smoother, warmer and more air - real music. IC’s and speaker cables are all nordost red dawns. By the way I sold my 402 and returned my 601’s - not worth the price difference compared to the 252. Just my honest opinion. Happy listening