Multiple Boot Chimes and Possible Arcing

[agg24]

I just finished a full logic and analog board recap on my SE/30. Upon initial power on I was greeted by clicking that sounds like sparks/arcing along with the standard boot chime. I immediately turned the machine off, then after a minute or so turned it on again. The clicking did not initially commence (and the chime still sounded), but after a second or two into the memory check, a single click (same arcing sound) happened again, and the computer chimed again. This happened 1 or 2 more times in the short period before I could turn it off again.

Any idea where I should begin to look? One thing to note is that the caps on my initial board were lower voltage than the typical numbers thrown around (almost all of them were 16V, instead of the typically quoted 25V). In one extreme case (3.9uF 250V), my cap read only 35V (due to difficulty finding this configuration, I replaced it with a 400V). For the other 16V caps, I replaced them with 16V ones, as I was not sure why my board was different, and didn't want to mess anything up. I could also see the CRT neck (and proper video appeared, although it was even further shifted to the side than it was before the recap), so I don't think that was arcing.

 

[agg24]

Turns out I was incredibly stupid and didn't connect the CRT neck grounding wire to the mount points of the CRT. This has happened to me multiple times before now. You would think I would learn...

Out of curiosity, what ill effects could/would you experience if you left the computer like this?

 

[agg24]

My adventures in stupidity continue:

I was adjusting the CRT to center the image and restore stock proportions, when I suddenly noticed that the well adjusted right side of screen was out of wack. I took a closer look and saw that the edge was slowly moving towards the center of the screen. A moment latter the movement sped up significantly and analog board C15 suddenly started venting dark smoke into the room.

According to this post, C15 is expected to be 3.9uF 5% 250VDC, though I replaced it with a 3.9uF 20% 400V. Is the higher tolerance likely the issue here? As I said in the OP, most of my stock caps were 16V, and I replaced them as such, even though most mentions I see for caps for the analog board are 25V. In particular for C15, my original board had a 35V cap instead of the expected 250V! Could this be causing some discrepancy elsewhere in the circuit?

Edit: With further reading I've found that 3.9uF caps are common as C1 on the 128k-Plus analog boards and they commonly fail. On those boards, they are 3.9uF 35V, just like my original cap was. Additionally, the cap is bipolar. Sure enough, after looking at the cap I pulled from the board, it was labeled "B P(S)", which I believe indicates that it was a bipolar cap. Is this common for SE + SE/30 analog boards?