Krell and CJ PV12

If I may I have two questions that I would like to have answered, and then maybe more to follow!

How often does my PV-12 need a complete tune-up preformed on it? And what would cost be and how long would it take to complete?

And more important; is it typically safe to use the PV12 and a Krell KSA 100 Mark-II Solid-State Amp together.

The reason I ask is:

I recently had a normal maintenance preformed on my Krell Amp along with a fan problem fix.

But after three hours of using the Krell along with the CJ PV12; I noticed a static noise coming from the left speaker.

After shutting down all the equipment I checked out the speaker cable connection or possible electronic interference that might be causing the static.

After slightly adjusting the banana connections I power up the equipment and the noise seemed to had disappeared, but after about 10 minutes the static came back and the Krell shutdown, and would no longer fire up!!!!!

I shutdown the equipment, removed the Krell and replaced it with my CJ MV52 Amp, and still notice a slight static noise from the left speaker.

I once again shutdown the equipment then flip-flopped the Mullard tubes in the V5 and V6 sockets and the noise completely disappeared and after 10 hours of use has not returned. (I though as I was flipping V5 and V6 and while removing the tube in V5 it felt that it may not have been completely seated?)

I had to return the Krell back to the company’s service department this past Friday and when I explained the above I was informed that a DC feed back from the PV12 most likely had cause the Krell to shutdown and that there is a very good chance that damage to the Krell has occurred as a result.

They said the would fix whatever damage there maybe under warranty since it had been lees then a week, but that I really should not use the PV12 along with the Krell? And if I did I should have the caps and tubes replaced once a year?

My friend has a PV9 and the same Krell and is wondering if the same would hold true for his unit?