Keyboard inverters/converters for terminals

Tony Duell ard.p850ug1 at
Fri May 22 11:29:55 CDT 2020

> But, I have some 3.25" drives that use same connectors as "standard" 3.5"
> drives, ("4 pin Berg"?)  EXCEPT 5V and 12V are swapped in their positions
> in the coneectors!

I have an Archive Sidewinder tape drive on one of my PERQs. The power
connector is the same as a 5.25" floppy drive power connector but the
2 voltages are +5V and +24V. At least the +5V pin is where you expect

I am told some Sun workstations (Sun 2's???) had a power harness to
feed both 5.25" drives and a Sidewinder. The only dfference between
the connectors was the colours of the wires going to them.

Of course plugging an RS232 cable (DB25, none of this DE9 nonsense!)
into a PC printer port (or a PC printer cable into an RS232 port) is a
good way to let magic smoke out of some TTL chips...

It didn't let any magic smoke out, but I once had to sort out a
10base2 ethernet system that was behaving very oddly. Putting a 'scope
on the cable showed a signal the likes of which I'd never seen on
ethernet before. I cranked the timebase down and recognised it.
Composite video (RS170-like). Some 'genius' had plugged an unused
ethernet T-piece into the BNC connector on the back of a VT220...


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