RFI or Capacitor issue?

We have an Audion Silver Night MKII, and it powers up silently. After it warms up a bit, I periodically get some light hissing in the left speaker, with an occasional high frequency noise that will rise in pitch for about 2-3 seconds. When I swapped the speaker cables, it moved to the right speaker. I've tried different tubes, and there is no difference. I've swapped tubes L/R, and there is no difference. I've got an appointment to take the amp into the distributor and have his tech look at it. He thinks that a capacitor is the likely culprit. But I want to make sure that I'm bothering him with a legitimate problem. I've not heard RFI or EMF noise that I know of, and wonder if that whining electrical sound could be interference from my wife's computer downstairs, or something of the sort.
Thank you all for your help.
I just turned off the computer, and am still getting the same periodic whining noise. Also, I am getting a light popping sound around the same time that the whining noise occurs. It does not sound like bad tubes--I've heard many of those. Maybe a tube socket? Resistor? Capacitor? I just want to make sure I'm not having a tech look at the amp for no good reason.
Does the noise change channels when you switch input cables?

Does the noise change when you gently rock/rotate each tube?
1) Do you mean when I cross the IC's Red to Black & vice versa? I have not done that yet.
2) I get a slight popping noise (like the one I described) if I gently rock the left channel 6922 tube. The rising electrical noise is intermittent.
This time, when the whining noise was happening, I gently rocked the left 6922, and it stopped--for a few minutes. Just to be clear, I don't mean microphonic tube whine. This sounds like an electronic static sound from the speaker, and it rises in pitch. It does not affect the playback of the music while it's happening.