Yes, that video was very helpful, even more helpful was your parts list. All but 2 caps were currently available, and the remaining two had suitable equivalents. I actually improved my technique and experience removing those leaky caps.
I tested the TNC again, 9600 baud after the recap, and no difference. However, the good news is another radio I have, same baud rate, works flawlessly. Same with the PC. My thought is impedance or levels are the issue with that TNC. I’ll probe with the scope when connected to that TNC, from the serial line back through the UART to see where it’s getting lost. Anyhow, the recap needed to be done regardless of my flawed serial port “experiment”, so I’m glad thats out of the way. This is a great resource as well as your videos, and thanks to all who offered some tips and advice, it is greatly appreciated. > On Jul 10, 2023, at 4:45 PM, bir...@soigeneris.com wrote: > > Yes, the M100 caps always need to be replaced. The RS232 output puts a > significant load on the -5V which makes for flaky LCD and RS232 operation. If > there are any traces under/around the caps that look dark they need to be > mechanically cleaned and neutralized (if corrosion was bad) to stave off > further corrosion. I have done a few videos on M100 recapping describing the > process. > > Jeff > > From: M100 <m100-boun...@lists.bitchin100.com > <mailto:m100-boun...@lists.bitchin100.com>> On Behalf Of Jesse Bertier > Sent: Monday, July 10, 2023 12:57 PM > To: m...@bitchin100.com <mailto:m...@bitchin100.com> > Subject: Re: [M100] Intermittent problem at higher baud rates on RS-232 > interface > > Hi Jeff, > > Thank you - I noted my serial # was after the 306000001 mark, and verified > the 330 ohm resistors are in fact on my board. I then took a closer look > over the board and noticed just about every electrolytic cap leaked. The > flipflop near the power supply area was also warm, so I powered it off and > may order some caps. I’m thinking at this point a recap before digging into > the RS-232 port any further would be a good place to start. > > This is a fantastic group, thank you all for the replies! > > >> On Jul 9, 2023, at 7:12 PM, <bir...@soigeneris.com >> <mailto:bir...@soigeneris.com>> <bir...@soigeneris.com >> <mailto:bir...@soigeneris.com>> wrote: >> >> The TPDD1, TPDD2, Backpack, etc. use 19200 successfully. If you can adjust >> the intercharacter delay on the TNC is might help. Also note that some early >> M100s had the wrong resistors in the output lines for the RS232 port. They >> fitted 5.6K from factory but they quickly revised that down to 330ohm as >> some devise would not work with it. >> >> I did a video on the factory mod a while back. A link to the technical >> bulletin is in the video description: >> >> https://youtu.be/KPFnwv_nDD8 >> >> Jeff Birt >> >> From: M100 <m100-boun...@lists.bitchin100.com >> <mailto:m100-boun...@lists.bitchin100.com>> On Behalf Of Gregory McGill >> Sent: Sunday, July 9, 2023 5:40 PM >> To: m...@bitchin100.com <mailto:m...@bitchin100.com> >> Subject: Re: [M100] Intermittent problem at higher baud rates on RS-232 >> interface >> >> there's no hardware flow control on the 100 with telcom >> use a better terminal and hardware flow control at any baud rate over 2400 >> >> >> On Sun, Jul 9, 2023 at 3:19 PM Jesse Bertier <berti...@gmail.com >> <mailto:berti...@gmail.com>> wrote: >>> First time getting my hands on a model T. I am attempting to connect to a >>> TNC at 9600 baud. I have both matched for 8,N,1 and 9600 baud. TNC works >>> with other PCs. I’m using TELCOM and set the parameters correctly. What >>> happens at 9600 baud is the text coming into the m100 is garbled mostly and >>> on occasion some valid words come across. When I set both to 300 baud, >>> works perfectly. It seems to be problematic if there’s a solid block of >>> text coming in, like a string of 20-30 words for example. >>> >>> Before I dig into the problem with the service manual and get out the >>> scope, does anyone know if these are supposed to work well at 9600 or up to >>> 19,200 ? Or, does the buffer or machine get overloaded at higher rates? >>> Is TELCOM the issue? >>> >>> Sent from my iPhone
