[Kenwood] TS-820S problem

[Kenneth G. Gordon]

OK, Gents, here is another one:

My TS-820S exhibits severe hum on its signal, both receiving and transmitting, when I 
attempt to use my VFO-820 external VFO.

I have checked the interconnect cable carefully and repeatedly, but have found nothing 
obviously wrong with the cable.

I have also installed a ground wire between the VFO-820 and the rig to no avail.

When I remove the interconnect cable and reinstall the jumper-plug, everything reverts to 
normal.

Is there some component involved that routinely fails?

I have, so far, found nothing on-line that describes such a problem

Thanks for any input you can provide.

Ken Gordon W7EKB