[Ham-Mac] Need help with PK-88 TNC

Sun, 4 Apr 2004 13:54:33 -0700 (PDT)

Hello Again All,

Well, I just hooked up the PK-88 to my Pee Cee and it
works great. So I guess it must be my cable like Chris
suggested. Now, how would I determine what connections
are there or which ones are missing? I guess that
would be hard for you guys to determine without the
schematic so I'll see what I can figure out.

Thanks again for everyone's assistance,
Carl KA5KAB

--- David Anderson GM4JJJ <[email protected]> wrote:
> Hi Carl,
> 		I don't have a PK-88 manual here anymore, so
> Unfortunately I can't 
> check the circuit diagram.
> PIN 12 is associated with the input line going to
> PIN 13. Can you check 
> where PIN 13 on the IC4 goes to, I imagine one of
> the DB-25 pins.
> 
> This will tell us whether it is the Receive data
> line or possibly a 
> hardware handshake line.
> 
> It may be that your modem cable is missing a line
> going to that input 
> and by putting a probe on teh threshold input you
> are simulating the 
> effect of having an input on that pin 13 by changing
> the threshold at 
> which pin 13 changes state.
> 
> 73
> 
> David
> On 4 Apr 2004, at 1:56 pm, Carl Miller wrote:
> 
> > Hi David and All,
> >
> > I am using a DB-25 to the Apple 8 pin connector to
> > connect the tnc to the Mac. I believe it's a
> standard
> > Apple modem cable and I have it connected to the
> modem
> > port.
> >
> > My terminal program is Microphone. It came with a
> > Supra modem I bought and I noticed it mentioned in
> the
> > PK-88 manual as one of the programs tested with
> the
> > tnc. It works great as long as I'm touching pin 12
> of
> > IC-4 with a probe of some kind.
> >
> > My settings on the terminal program are:
> >
> > 1200 bauds
> > 7 bits/character
> > even parity
> > handshake- xon/xoff
> > modem connection- telephone port
> > 1 stop bit
> > the only function I can't set according to the
> manual
> > is "full duplex". I don't see that setting in any
> of
> > the Microphone menus.
> >
> > By the way, and I forgot to mention, when I first
> > discovered this unusual procedure I thought
> perhaps it
> > was a bad IC socket so I removed IC-4 from it's
> > socket, removed the socket, and soldered the chip
> > directly to the PCB. It didn't help.
> >
> > If you need any further info just let me know.
> This
> > thing is really got me confused.
> > Thanks again,
> > Carl
> >
> >
> > --- David Anderson GM4JJJ <[email protected]>
> wrote:
> >> Carl,
> >> 		Can you tell us the details of how your serial
> >> lead is wired? Also
> >> what software, is it a regular terminal program
> like
> >> ZTerm or what?
> >>
> >> 73
> >> David
> >>
> >>
> >>
> >> On 4 Apr 2004, at 1:15 am, Carl Miller wrote:
> >>
> >>> Hello All,
> >>>
> >>> I am new to the list and I already need help
> with
> >> a
> >>> problem.
> >>>
> >>> I have a PK-88 TNC that I am trying to use with
> my
> >> old
> >>> Macintosh Classic II.
> >>>
> >>> The problem I am having is that the PK-88 will
> not
> >>> accept commands from the terminal. That is,
> until
> >> I
> >>> touch a probe or other metallic object to pin 12
> >> of
> >>> IC-4, a 75189 quad line receiver. Once I power
> the
> >>> thing up and touch a metallic probe to pin 12
> the
> >>> thing works great, I can send it commands, I can
> >> do
> >>> the loopback test with no problem. But once I
> >> remove
> >>> my probe, the thing goes deaf again. I also
> >> noticed
> >>> that if I remove the probe, then touch pin 12
> >> again it
> >>> gives me the cmd: prompt. Then I can communicate
> >> with
> >>> the tnc again.
> >>> According to the Texas Instruments data sheet on
> >> this
> >>> particular chip, pin 12 is the threshold control
> >> pin.
> >>> But, since I am not an EE, I don't have a clue
> >> what
> >>> that means. The funny thing about pin 12 is that
> >> it
> >>> isn't connected to anything from what I can
> tell.
> >> It
> >>> certainly isn't noted on the schematic.
> >>>
> >>> What gives here? Is this thing posessed or what?
> >>>
> >>> I would certainly appreciate any help or advice.
> >>> Thanks in advance,
> >>> Carl KA5KAB
> >>>
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