K3: No measurable voltage on band data lines?

[Dan Levin]

I'm still trying to debug my problem with the Top Ten band decoders and my
K3 (s).  When I put a volt meter on the band data output pins of the K3's
ACC connector, I don't see any positive voltage (all the pins read zero).
When I connect the ACC pins to the Top Ten decoder via an appropriate cable
(thus bringing the decoders pull-up resistors into the picture), I see a
non-zero voltage on the "high" pins, but only between 1.6 and 2.2 volts -
not 5 volts.  Without the connection to the K3 in place, the same pins
measure 5 volt (due to the pull-ups).

Is this normal - in particular, is it normal not to be able to measure a
positive voltage on the "high" pins of the ACC connector with nothing other
than the meter attached?  I realize that these are "open collector", but I
would have expected to read some positive voltage.

                   ***dan, K6IF

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[Joe Subich, W4TV-3]

> Is this normal - in particular, is it normal not to be able
> to measure a positive voltage on the "high" pins of the ACC
> connector with nothing other than the meter attached?  I
> realize that these are "open collector", but I would have
> expected to read some positive voltage.

yes, this is normal.  "Open Collector" - or in the case of the
K3 "Open Drain" - means that the output devices do not source
any voltage and there are no "pull up" resistors to provide
output voltage when the drivers are in the "off" state.

73,

   ... Joe, W4TV
 

 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Dan Levin
> Sent: Thursday, October 30, 2008 9:08 PM
> To: [hidden email]
> Subject: [Elecraft] K3: No measurable voltage on band data lines?
>
>
> I'm still trying to debug my problem with the Top Ten band
> decoders and my K3 (s).  When I put a volt meter on the band
> data output pins of the K3's ACC connector, I don't see any
> positive voltage (all the pins read zero). When I connect the
> ACC pins to the Top Ten decoder via an appropriate cable
> (thus bringing the decoders pull-up resistors into the
> picture), I see a non-zero voltage on the "high" pins, but
> only between 1.6 and 2.2 volts - not 5 volts.  Without the
> connection to the K3 in place, the same pins measure 5 volt
> (due to the pull-ups).
>
> Is this normal - in particular, is it normal not to be able
> to measure a positive voltage on the "high" pins of the ACC
> connector with nothing other than the meter attached?  I
> realize that these are "open collector", but I would have
> expected to read some positive voltage.
>
>                    ***dan, K6IF
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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