Good advice; the most likely culprit (because it's indirectly connected to the outside world with its static, lightning, ground loops etc.) is M35, a (1)4584.
The only other IC would be M24, a 40H032 (which could probably be replaced with a 74HC(T)32). m ----- Original Message ----- From: "John Gardner" <gof...@gmail.com> To: <m...@bitchin100.com> Sent: Wednesday, August 02, 2017 12:23 PM Subject: Re: [M100] Model 100 serial port > ...the problem is somewhere between the db25 and the UART... > > Most likely. I'm no great troubleshooter, but if I may... > > Set up a test file which contains a long series of 0xAAs, as in > > 10101010... > > Send the file at a baud rate which is easy for you to see with > > whatever you've got for test equipment. > > While the file is being sent, look for the signal. When you find it, > > the fault is between that point & the DB25. I expect the problem > > is either a PCB trace, solder joint, a defective buffer, or the DB25 > > connector itself (It happens...). > > There's also a small possibility that the UART is at fault, but not likely. > > I'd be interested to hear what you find. > > > > > > On 8/2/17, John R. Hogerhuis <jho...@pobox.com> wrote: >> Well the good news is the problem is somewhere between the db25 and the >> UART :-) >> >> -- John. >>
