Seventh Circle Audio

I've got a C84 channel that was working fine for 6 months or so but is now making weird intermittent noises. I reflowed all of my solder last night and ran the pre for an hour without an problems. This morning I recorded another hour or so and there are several spots where this sound or something similar pops up. It doesn't seem to matter whether I have a mic patched in or not.

Any bright ideas? I used to have a second C84 but no longer do so I have nothing against which to check my voltages.

Thanks,

Ryan

Here's an audio file of the noise:

http://www.lansingrecording.com/sca/c84.wav