[Packet] MFJ-1270B Help

[Bob Donnell]

You might also have gotten a TNC that's not using its original user-oriented 
firmware.  So the first question would be what's the brand and model of the 
TNC?   And you might want to view the EPROM (s) on the board in the TNC, and 
include information about any chips with paper labels you find within.  Those 
of us that have "a history" in the "packet racket" can then better help you 
with more info.

If it IS a TNC-2 clone, with the DIP switches on the back, it's important that 
only one serial port baud rate selector switch (the first 5) and one radio 
port baud rate selector switch (the last 3) be in the on position.  They 
literally connect one of the outputs from the baud rate generator to the 
serial I/O chips, and if you have multiple switches on, then the baud clock 
will probably be garbled, resulting in unknown (and potentially variable) 
baud rates.  Also, most models of TNC-2 clones use an op-amp as the RS-232 
line transmitter chip, and the usual selection for that part had only a 
marginally fast enough slew rate to operate at 9600 baud.  So I would suggest 
that instead of initially setting the serial communications as suggested by 
Doug, at 9600 baud, that 1200 baud would be better.  If memory serves, that 
would be setting switch 2 on, instead of switch 5. 

73, Bob, KD7NM.



On Tuesday 22 November 2005 10:19, W0OXJ wrote:
> New to packet and just bought this TNC.It just came out of service.For the
> life of me I cannot get my PC to talk to this device.It sends and receives
> at all baud rates but the characters are jumbled and the CR/LF is
> intermittant based on config.
>
> .I have changed everything in the PC,comm port,terminal program,drivers and
> tried every comm port parameter available.I tried the comm setup on Winpac
> 6.80 and Hyperterm but am using Bitcom until I establish communications.I
> have verified all TNC straps and replaced the button cell.The RS-232 cable
> has pins 2-8 and 20,22 wired on the TNC end and a db-9 plugs into the PC.I
> assume this is not a null modem as I can receive characters and the enter
> key will move the cursor.I have 12vdc applied from a MFJ 500ma wall wart.
>
> I understand there are TNC commands to effect the communications but
> obviously I can't access the TNC for command entry.
>
> I have worked on lots of rs-232 over the years but this one has me stumped.
>
> Any help and guidance would certainly be appreciated.
>
> 73,
> Bob
> W0OXJ
>
> ______________________________________________________________
> Packet mailing list
> Home: http://mailman.qth.net/mailman/listinfo/packet
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:Packet at mailman.qth.net
>
> List Administrator David Barlitt (KF4AWU) mailto:kf4awu at qsl.net