DEC H7822 power supply

[Tony Duell]

On Mon, May 9, 2022 at 2:27 PM Paul Koning via cctalk
<cctalk at classiccmp.org> wrote:
>
> Why would you expect a transceiver power supply to be isolated from system ground?  The transceiver logic ground (via the AUI connector) is tied to the system ground.  It is the coax that is isolated from the system ground, not the bulk of the transceiver circuitry.


An external transceiver has an internal _isolated_ DC-DC converter and
the signal lines are transformer-isolated. So the electronics is
isolated from system ground.

If you have an internal transceiver you either have to keep that DC-DC
converter or run the electronics off an isolated output on the power
supply.

Note that the outer of the BNC connector is isolated from the system
casing (which is grounded). In some cases those insulating bushings
are actually ceramic capactors (!).

-tony



>
>         paul
>