Can you post a recording of the noise?
Were you off the air when you had the 950SDX out or where you using the '718 and the '746 while you didn't have the '950? Was there really a correlation with reinstalling the '950 like you listened the evening before you put the '950 back and there was no noise and then when you fired up the rigs the next day after putting things in place, you had noise?
You might want to go through the RFI-location checklist at:http://rfiservices.com/tips.htm
Because an S9+ noise level is fairly likely to be coming from your own house.
The basic idea is to run the rig from a battery and shut down the rest of the house.
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The astron tripping off on 40m suggests that something *has* changed with your antenna system somehow. Do you use antennas where you'd notice SWR changes directly? Losing a coax shield connection while using a tuner to match your antennas could cause a huge noise ingress and RF getting into the Astron. Astron supplies are fairly prone to tripping off if you run RF currents through them. My VS-35M used to shut down on 30m all the time when I was using an end-fed wire.