[GreenKeys] Re: Dovetrons

[John Lawson]

   This is a fairly common 'gotcha' when connecting machines from different 
eras to one another.  It's truly a bummer that you've had your mobo 
scrambled - at least your machine's still basically functional and the 
contents of your HD are safe.  I've had much more terrible results...

   There is a line filter, sometimes called by the generic 'Corcom' but in 
reality made by various companies, CorCom included. If this has broken 
down it would tend to produce this fault, and it *would* be about 60Vac.

   Also - is the Loop Supply bleeding to something? Or do you hev the 
Tempest version with just TTL outputs, requiring a seperate loop-keyer.

   Last - have you got these units perhaps plugged into outlets on either 
side of neutral?  I once sold a computer and printer to a writer. Back in 
the day, that meant 'character printer' - the 12 cps daisy-wheel type. He 
objected to the noise, we offered him a 'muffler cabinet'.  He chose 
instead to have a 35' cable made, and stuck the printer in the kitchen, 
computer in the office. He lived in an old house with knob-and-tube 
wiring, two-prong outlets - you can hear this coming. 120VAC common-mode 
across the 5V chassis grounds made a little sci-fi battlefield out of the 
traces on the computer mobo, fried the printer - the only thing left 
undamaged was his long cable.

  If the problem persists, you can use a small 1:1 audio transformer of 
suitable impedance to isolate the two ground systems....  but I'd sure dig 
in and find out why the Dovetron is presenting such a solid leak current 
in reference to it's internal grounds.

   John  KB6SCO