Hi, I'm not familiar with the 102, but on the EU Olivetti M10, the internal modem was disabled by removing a few parts (including the line transformer) and shorting out the RX operational amplifiers on the solder side of PCB. I've tried to restore the functionality of the internal modem of my Olivetti M10 but I'm still missing some bits. By the way, the internal modem design on these machines were hardwired to the BELL 103 standard, so it wouldn't be of much use in Europe in the '80s (nor it would pass any telecom licensing in those years). On my M10 I've re-calculated the RX and TX filter to work with CCITT V.21 standard and hacked the PCB to allow the modem IC to use V.21 modulation instead of the Bell 103 one. By the way, I have a small VOIP pabx at home with analog to voip converters, so I can test and use the old modems and the old phones. HTH Frank IZ8DWF
On Thu, Feb 3, 2022 at 1:04 PM Cedric Amand <[email protected]> wrote: > > Hello everyone, > > I'm a new member, out of Belgium, I have a dozen of vintages PCs, I > especially likes laptops. I'm an electronics engineer which helpes for > fixing. Thanks for welcoming me and thanks to whoever created this in the > first place. > > I'm trying to make the internal modem of my Tandy/RS Model 102 work again. > > I've connected it to a small home phone exchange (pabx) so that I have real > proper vintage phone lines , but the same problem occurs on my home phone > line (which is not PSTN anyway, it's an emulated analog line turn into voip > by a modern cable modem router) > > I absolutely wanted to have my own "lab" of proper PSTN lines so that's why I > have my little PABX from the 90s; which gives me the possiblity to experiment > with modems. > > My problem is ; my model 102 does not pickup the line. > A regular analog phone does, a good old USRobotics Courrier 56K does, but the > T102 does not. > > I have the proper Tandy grey/beige(rather pink now) cable > It's inserted in the right way. My init string (STAT) is starting with M, for > internal modem > > If I put a phone on the gray line, and "pink" in the PABX ; i can hear my > PABX's dial tone, until I make the M102 dial, in which case the phone goes > silent (which is normal). > > But the PABX doesnt show the line as beeing picked up (a led should turn > red), I can hear the M102 pulse dialing "in the void", but to no end... The > PABX supports pulse dial. I tried 10pps and 20pps. > > But it seems the problem is not dialing, it's the actual, i'd say > "electrical" pickup of the line. > It seems either the voltages are not right, or something is not working like > it should. > > I tried BASIC with "CALL 21200" (which pickups the lines) you can hear the > relay click, but again, the PABX does not see that as someone picking up a > phone. > > I have an European M102 (could that be an issue ?) My "phone line" (vintage > PABX) is a european (belgian) one. > However the M102 has been "upgraded" by a REX# v2.0 rom by the previous > owner, that may be an issue (this upgrade was not my doing. I can barely use > REX.) I'm with TSDOS101 > > It's unclear if, eventually, the modem section could need a repair (recap or > smth) > Another possilbity would be that the tone i'm giving it (440Hz over here) is > not recognized (seems to be 600Hz in the US), but I find this unlikely this > would be software controlled, and my M102 is a Belgian model it even has the > "RTT" (telco of the time) sticker on it > > I'm out of ideas. > Any help greatly appreciated
