If you look at the schematics for the VT-100 (which are available on bitsavers) as well as most terminals of the day used the Motorola MC1488/1489 driver pairs [early on, TI marked them as 75488/75498 but I doubt you'll see that old]. Anyway, for any terminal of those times, I'd be surprised if the later devices (like VTx20 series) did not them [the issue with these devices is you need all of 5 and +/- 12 volts]. These terminals are new enough that they might have used MAX232 (single 5 v power - there are even 3.3v versions these days). All of these devices are very available online. I would suggest putting high quality (*i.e.* auget style / machined pins) sockets. The nice thing about 1488/1489 is that they were doped to fuse the output section on failure, so just replacing them will in fact resurrect most serial port failures. Frankly, I never understood why more manufacturers did not put them in sockets for easy replacement. That said before you open up the case, I make sure you are cabled correctly. If you are using so-called 3-wire cables, then you need to ensure RTS/CTS [4-5] are strapped and DSR/DCD/DTR [6/8/20] are also strapped. The terminal will ignore any I/O unless it sees these pins asserted. On Thu, Apr 29, 2021 at 3:11 AM Tom Ivar Helbekkmo via COFF < coff@minnie.tuhs.org> wrote: > I've got a number of DEC terminals, ranging from the VT220 to the VT520 > (sadly, I got rid of my VT100 and VT102 many years ago, before I started > collecting DEC equipment instead of just using it), and some of them > have one or more burned out serial ports. Before I start taking them > apart to find out what chips were used, I figured I'd check if any of > you folks happen to know. I'd like to order a stash of replacements, > and it would be nice to have them handy before I clear the work bench to > start dismantling terminals... > > Oh, and for the record: the Q-bus PDP-11/23 uses 9636ACP and 9637ACP for > output and input, respectively, while the VAX-11/630 substitutes a > 9639ATC optocoupler for the 9637ACP differential receiver. (I have a > couple of spare CPU boards with damaged ports, as well, so these are all > on my shopping list already.) > > -tih > -- > Most people who graduate with CS degrees don't understand the significance > of Lisp. Lisp is the most important idea in computer science. --Alan Kay > _______________________________________________ > COFF mailing list > COFF@minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff >