[comp.sys.mac] Bad Serial Port

dencisco@eos.UUCP (David Paul Encisco) (01/06/90)

I wouldn't be concerned if this was the first serial port that blew on my
Mac IIx, but unfortunately this is my forth blown serial port in two monthes
on a year old machine. I practice safe Mac: never unplug anything while the
machine is on. I've also checked for power surges and found no problems and
we connected my micom line to another Mac and it works great!

The message I get when using Versaterm:"Sorry the communications port is in
use by another program. You may continue off-line or try to use the
communications port anyway." This is in fact false, I'm not using another
program nor can I use the port anyway. MicroPhone has a more definitive error
message: "OS Error -28 occurred at point 500", which at least informs me that
the I/O driver is not open.

Has anyone else had similar problems with the serial port?
Our hardware support group is a little apprhensive to send the mother board
back for the forth time. Obviously they think the problem is me.

Thanks,
Dave

andyp@gvgpvd.GVG.TEK.COM (Andy Peterman) (01/07/90)

In article <5923@eos.UUCP> dencisco@eos.UUCP (David Paul Encisco) writes:
>I wouldn't be concerned if this was the first serial port that blew on my
>Mac IIx, but unfortunately this is my forth blown serial port in two monthes
>on a year old machine. I practice safe Mac: never unplug anything while the
>machine is on. I've also checked for power surges and found no problems and
>we connected my micom line to another Mac and it works great!
>
>The message I get when using Versaterm:"Sorry the communications port is in
>use by another program. You may continue off-line or try to use the
>communications port anyway." This is in fact false, I'm not using another
>program nor can I use the port anyway. MicroPhone has a more definitive error
>message: "OS Error -28 occurred at point 500", which at least informs me that
>the I/O driver is not open.
>
>Has anyone else had similar problems with the serial port?

I don't think you've "blown" your serial port.  It sounds like a problem
with the Chooser.  Have you been running a MIDI program recently?
If so, this problem can show up.  (Especially with Apple's MIDI
Manager!).

To fix it, find one of these MIDI programs, start it up and then quit
it, and finally open and close the Chooser.  This is the only way to get
the port working again!!  I first came upon this problem after loaning
my Mac to a friend who was using it for some MIDI work.  When I got it
back, the serial port was hung up and I spent hours trying to fix it.  I
was able to hack into the System code and get it reset, but I cannot
remember what it was I did.   The method above is suggested by Apple in
their documentation on the MIDI Manager.  Its a known bug with the
Chooser.

	Andy Peterman

wiseman@tellab5.TELLABS.COM (Jeff Wiseman) (01/08/90)

In article <5923@eos.UUCP> dencisco@eos.UUCP (David Paul Encisco) writes:
>I wouldn't be concerned if this was the first serial port that blew on my
>Mac IIx, but unfortunately this is my forth blown serial port in two monthes
>on a year old machine. I practice safe Mac: never unplug anything while the

Does "Blown" mean "exhibits the symptoms described below"?

>The message I get when using Versaterm:"Sorry the communications port is in
>use by another program. You may continue off-line or try to use the
>communications port anyway." This is in fact false, I'm not using another
[stuff deleted]
>Has anyone else had similar problems with the serial port?

Dave,

I have an old (I think the original shareware release) of versaterm and I have
seen this same thing happen but there is nothing wrong with my port. I use two
or three types of terminal programs (all old, freeware variety). I have
discovered that if some of them are set up to leave DTR active (ie. hold onto
the line) and I quit the program and then start a different terminal program, I
can get the symptoms you describe. However, if I "...use the communications
port anyway..." it works fine. Also, if I power down my machine (an SE) and
then reboot, the problem goes away.

I do not know if this is your problem but I hope this information helps

-- 
Jeff Wiseman:	....uunet!tellab5!wiseman OR wiseman@TELLABS.COM