[Elecraft] USB/RS-232 Cable

[JJ]

I have a K3 and use a SDRPlay RSP1 as a panadapter.  Last night I noticed a
huge jump in noise and then noticed a strong, wide, cruddy signal every
120hz which would indicate a power supply problem.  This problem is new.  I
have been using this cable for a few years with no problems.  I do not know
the cable's provenance .
I finally traced the source of the noise to my K3 USB to RS-232 computer
connection.
When I disconnect the cable from the K3 the noise disappeared.  The noise
only occurs when the cable is activated.  If turn on the K3 and start
whatever SDR program there is no noise.  As soon as I activate the
connection between the K3 and my computer with OmniRig the noise starts.
The cable appears to otherwise be OK in it's operation.
I don't have another cable to test to see if it is the cable or not so I am
going to order another.
Has anyone else ever experienced this problem?  I'm hoping it's not the K3
Thanks,
Jon WS1K