I made some progress this weekend. I've got the C4S boards built and ready to go in, so when I get the time, I'll get them in and wrap up the build.
But, I had a couple of questions. I made a really silly error and had one of the rectifiers leading from the transformer placed in the wrong direction in the initial power supply test step. When I plugged the cable in, I heard a buzz for about a second, then a faint pop from the fuse giving way. After remedying the situation, I replaced the fuse, but at first with a 1.6A fast blow which didn't stand a chance. 2A fast-blow fuse also blew instantly. But, placing a 3A fast-blow fuse in there held. Voltages checked out fine.
I then continued and measured with the 300B tubes in place. When I turned the amp on, I heard another very slight pop, but the fuse didn't give way. The tubes were glowing, and I heard a very slight hum sound coming from the amp itself. I thought it was odd, so I unplugged it, and check everything again. I couldn't find anything, and when I plugged it back in for the tests, I didn't hear the pop or buzz this time. The measurements were within spec. What are your thoughts on why that buzz showed up but disappeared after powering off -- and do you think the transformer will be okay?
And, will there be any noticeable effects of one side (10U vs 15U & 53U vs 65U) having a slightly higher VDC measurement? I believe 53U was about 75.5-76V and 65U was about 77V. I did notice that the 300B tubes had varying measurements: [74mA/6.0mA/V] vs [72mA/5.8mA/V]
Of course, the driver testing and actual listening will grant more insight, but I'm wondering if I should be paying extra close attention to something before arriving at that point.
Edit: @PB, would you recommend I disconnect the UF4007's from the transformer and perform the transformer test just to be certain? Or do you think that things should be okay given that I've passed high voltage power test?