"Pin 1" problem refers to an issue originally identified in professional
and broadcast audio equipment where "pin 1" of the XLR connector was not
connected directly to the shielded case *at the connector* but instead
connected to the circuit common elsewhere in the device in question.
> On SUB-D-25 pin 1 is shield, so I guess you refer to shielding/ground
> loop problems? The now much more common SUB-D-9 only has data ground,
> on pin 5... and pin 1 there is DCD.
A properly installed DB25 (RS-232C) bonds the shell, pin 1 (shield) and
pin 7 (signal ground) to the circuit board ground plane and device case
at the connector. A properly installed DB9 (EIA/TIA 574) bonds the
shell and pin 5 (signal ground) to the circuit board ground plane and
device case at the connector.
Any device that does not bond the shell of a DB series connector and
all "grounds"/signal returns to the chassis and circuit board ground
plane *at the connector* has a potential "pin 1 problem". In the case
of the Signalink USB, the "pin 1 problem" is on the RJ-45 since both
audio and circuit (PTT) returns float on the circuit board before
returning to the ground plane via long/thin traces. The device
violates proper design principles by *not* properly bonding all
"grounds" and circuit returns.
73,
... Joe, W4TV
On 7/28/2012 5:55 AM, Holger Schurig wrote:
> What do you mean with "Pin 1 problem" ? On SUB-D-25 pin 1 is shield,
> so I guess you refer to shielding/ground loop problems? The now much
> more common SUB-D-9 only has data ground, on pin 5... and pin 1 there
> is DCD.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[email protected]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
