I just received a 2 tube 572B amp. The tubes have been replaced with new. The DC blocking capacitor has been replaced as well, the old one blew up. From my understanding the guy that had it before drive it hard. Over a 150 watt DK into it. I was told that there was a device that would shut it down and feed the power thru without going into the amp. Which is exactly what it is doing. I have plate voltage and the filaments have voltage. Any idea what I should look for or has anyone else ran into this problem? Any help would be greatly appreciated. Thanks in advance.