[Elecraft] Digout1?

Sat Aug 10 11:42:08 EDT 2013

I ended up stripping down the network of wiring to just the Elecraft
supplied cable the PR6 and the KAT500. It still pulled the PR6 line active.
I then wised up and consulted the PR6 schematic and figured out the
problem. The PR6 is a 12V only device with a transistor interface to
activate the relays and provide power to the FET stage. The KAT500 is a 5V
device. So any connection to the KAT500 even through the 4.99K resistor is
to a lower voltage point, either 5v or gnd. The result is the KAT500 will
often be capable of drawing enough current from the PR6 interface to turn
on the relatively high gain 2N3906 and activate the PR6 as a result. BTW,
the KAT500 can draw this sufficient current whether or not it has power
connected (power supply lead physically removed).

The solution is to not rely on the KAT500 being innocuous and just
disabling the KPA500 menu item for INHIBIT. The solution is to physically
break the PIN11 connection from the K3 which I plan to do by taking another
pin out of the supplied Key Line Interrupter.

jim

On Sat, Aug 10, 2013 at 9:42 AM, Dick Dievendorff <dieven at comcast.net>wrote:

> KAT500 firmware initializes the INHIBIT (pin 11 of the ACC connector, pin
> 16
> of the microcontroller, PORTF bit 4), as a hi-Z input (the TRIS bit is 1
> for
> 1nput), never changes the TRIS bit, and doesn't ever reference the value of
> the input port bit.
>
> As I read the schematic, even if the KAT500 configured the pin as output
> and
> pulled that low, there would  be a 4.99K series resistance.  It's perhaps
> intended as an input to the KAT500, but it's not used in firmware.
>
> I don't know what I could change in firmware to have less effect on the
> INHIBIT line.
>
> The KAT500 instead interrupts the amplifier key line to "inhibit" the
> amplifier, which works with more amplifiers than the KPA500.
>
> However physical testing trumps design intent...
>
> Dick, K6KR
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Cady, Fred
> Sent: Friday, August 09, 2013 20:25 PM
> To: 'Jim Miller'; 'Elecraft Reflector'
> Subject: Re: [Elecraft] Digout1?
>
> Hi Jim,
> The schematic I have doesn't show the pin 11 inhibit pulled low in the
> KAT500. It goes to the microcontroller through a series 4.99K resistor.
> But what it is used for in the KAT500 is an interesting question.
>
> Back to your original question, I have the K3-KAT-KPA set up and use
> Digout1
> to switch the PR6. I'd have to check more closely but I don't think the KPA
> or KAT is pulling pin-11 low all the time.
>
> Cheers,
> Fred
>
>
> Fred Cady
> fcady at ieee dot org
>
> > -----Original Message-----
> > From: elecraft-bounces at mailman.qth.net [mailto:elecraft-
> > bounces at mailman.qth.net] On Behalf Of Jim Miller
> > Sent: Friday, August 09, 2013 6:18 PM
> > To: Elecraft Reflector
> > Subject: Re: [Elecraft] Digout1?
> >
> > I found a thread on this reflector that mentions the PIN11 problem. It
> > was from April of this year and I had forgotten it. I'll just break
> > another pin off in the Key Line Interrupter to solve the problem.
> >
> > Another mystery however is why the INHIBIT line is there in the first
> > place. Its operation isn't described in the KAT500 and the KAT500 has
> > it permanently pulled low. Note that the KAT500 document calls it
> > INHIBIT (inferring a positive active polarity) while the KPA500
> > document calls it INHIBIT# (inferring active low polarity.) Since I
> > have the INHIBIT IN disabled via the KPA500 menu nothing is happening
> > here anyway between them.
> >
> > In neither document is the purpose described. Note that this is not
> > the PTT
> > (PIN10) which is well documented and working fine for me.
> >
> > Still not clear either why the KAT500 would have this line pulled low.
> > According to the KAT500 schematics PIN11 is passed through and only
> > sensed by the microcontroller via a 4.99K/0.1uf network. The cable
> > when disconnected from the KAT500 but still connected to the K3/PR6
> > doesn't interfere with the DIGOUT1 function. Only when the KAT500 is
> > connected.
> > BTW, for this test the cable going to the KPA500 is not present so
> > neither the cable or the KPA500 can be contributing.
> >
> > Looks like it's time to open the KAT500F.
> >
> > jim
> >
> >
> >
> >
> > On Fri, Aug 9, 2013 at 3:32 PM, Jim Miller <jim at jtmiller.com> wrote:
> >
> > > I've got the K3/KAT500/KPA500 all chained together with the Elecraft
> > DB15
> > > accessory cables.
> > >
> > > I'm now in the process of connecting up the PR6/DIGOUT1 enabling
> > line.
> > >
> > > I've removed the jumper in the PR6 and connected the control signal
> > to the
> > > PR6 to DIGOUT1 and all works well; switching the CONFIG: DIGOUT1
> > > menu
> > entry
> > > causes the relays in the PR6 to switch audibly.
> > >
> > > However when I connect up the DB15 chain to the KAT500 the DIGOUT1
> > line is
> > > permanently pulled low.
> > >
> > > Referring to the cable diagram and the KAT500/KPA500 connector
> > callouts it
> > > appears the KAT500/KPA500 use the same PIN11 as DIGOUT1 for an
> > INHIBIT#
> > > function.
> > >
> > > I disconnected the KPA500 from the chain and the KAT500 appears to
> > > be pulling this line low all the time.
> > >
> > > Do I need to remove PIN11 from the cable as well? I already have the
> > > Keyline interrupter installed which has PIN10 removed.
> > >
> > > Confused...
> > >
> > > jim ab3cv
> > >
> > >
> > >
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