[Ham-Mac] Need help with PK-88 TNC
Chris Smolinski
[email protected]
Sun, 4 Apr 2004 09:22:28 -0400
Just a wild guess, but perhaps the cable from the Mac to the TNC is
not properly wired for your needs? The fact that touching the
threshold control pin makes it work makes me suspect that. Touching
the pin may be putting a charge on that input, shifting the detection
threshold level. Anyway, a wild guess on my part. Buzz out your
modem cable and see how it is wired. I've had oddball Mac modem
cables before that are not "quite right". ;-)
>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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--
---
Chris Smolinski
Black Cat Systems
http://www.blackcatsystems.com