On Wed, Oct 25, 2023 at 12:53 AM Doug Jackson <[email protected]> wrote: > > I see that there are component changes around the Telephone Modem interface. > > Here in Australia, we used CCITT for our modem standards, so I modified my > M100 to use CCITT V.21 tones (1750/1850Hz) instead of Bell 103 tones > (1270/1079Hz) - It was a massive undertaking for a Trainee Technical Officer, > but I was pretty pleased when it worked.
unrelated to the original topic, but I did the same modification to my Olivetti M10, however the original modem was "disabled" by removing some components and short-circuiting some of the opamp inputs. So it's still not working, but I've had no time to troubleshoot it yet. Do you have perhaps a list of the modifications? Other than setting the modem IC for CCITT mode, I had to recalculate all active filters for the new tone frequencies, and allow for originate/answer filter change (as in the original design, but adds a bit to the filter complexity). > > Direct Connect M100 - No need for my Acoustic Coupler any more!... Of course > it didn't meet the Australian Standard for line isolation ;-) I'm interested in this also, what do you mean? In the early 80's we weren't allowed to connect "random" devices to the phone line (that's why acoustic couplers were so popular), but that's only because all devices would first need an official technical approval and that costed too much for small manufacturers. I believe most direct connect modems would get approved if they were tested. best regards Frank IZ8DWF > > > On Wed, 25 Oct 2023 at 09:20, Ken St. Cyr <[email protected]> wrote: >> >> I don't think you're wrong - all of my M100s are 110CH1X. 1010 certainly >> seems to be an earlier revision of the board. Just curious - what's the >> date code on the CPU? I can't make it out with the cap in the way. Also, if >> you're up for dumping the ROM, it would be interesting to compare it to a >> 'released' version. >> >> //Ken S. >> _______________________________ >> From: M100 <[email protected]> on behalf of Josh Malone >> <[email protected]> >> Sent: Tuesday, October 24, 2023 12:07 PM >> To: [email protected] <[email protected]> >> Subject: Re: [M100] Possible M100 prototype. >> >> Off the top of my head, I don't recognize that artwork number: PLX 1010H1X. >> Am I wrong here? >> >> And, wow, this thing is bodge city. Almost like the Tandy 1400FD that I >> have. (that I still don't know the story behind the bodges) >> >> -Josh >> >> On Tue, Oct 24, 2023 at 11:38 AM <[email protected]> wrote: >> >> All, >> >> >> >> I recently attended Tandy Assembly 2023 and Eric Dittman asked me to recap >> an M100 that had belonged to Frank Durda an engineer at Tandy. I did not pay >> much attention to it at the time but when I took it apart last night, I was >> not sure what I was looking at. The PCB is a US type but has dozens of >> modifications and is a bit different than any other one I have seen. >> >> I then noticed it was missing the TRS-80 Model 100 badge, the FCC label and >> it had no serial number. Now I’m thinking this might be a prototype machine. >> I took a few quick pictures, link below. I plan to take some higher quality >> images and document the modifications as well as I can. The goal it to get >> it working but not alter it more than required. The only caps that look like >> they are leaking at the 10uf (which are normally the worst ones), so I will >> start with those and the memory battery and see if it springs to life. >> >> https://1drv.ms/u/s!AtH4vpaZnzX7mKBV07xl8qlMDuc6QA?e=UfFBVx >> >> Thoughts? >> >> Jeff BIrt
