bryan@mothra.cs.utexas.edu (Bryan Bayerdorffer) (01/14/88)
So what gives with this *&^#! A2000 parallel port, anyway? Perhaps I should be more specific. Yesterday I decided to hook up my venerable IDS460 to the parallel port. This printer had always worked flawlessly with my A1000. Alas, sending even the most simple text turns my printer into the most spectacular cornucopia of garbage. Aha, says I, I must have blown it when I rewired the computer end of the cable to compensate for that excremental gender change. Nope, it all checks out, assuming the pinouts given in the little A2000 book (which are the same as the ones posted a while ago) are ok. (Are they?) The next logical conclusion is that the parallel port is trashed, or that the printer has breathed its last. Negative on both counts, as verified by hooking the printer up to a different A2000 (same garbage), and the printer to a different computer (ok). Now for a list of symptoms and conditions: 1. The garbage produced is almost always identical for a given input, so it's some deterministic failure mode. 2. Printing a series of identical characters almost works--only the first character is trashed, e.g. aaaaa -> !aaaa, bbbbb -> #bbbb 3. Turning the monitor on and off causes the printer to linefeed (!!!) 4. The printer has given me a couple of nasty static-zaps after being on for a while. It's never done this before, nor does it act this way when hooked up to something other than an A2000. 5. The cable I'm using is longish (5-6 feet) for a parallel hookup, but it's never given me any trouble before. Symptom 2 suggests that the data outputs (of which I'm only using bits 0-6, by the way) don't have enough time to drive the wires in the cable to acceptable levels before the first strobe comes along, but after that everything works because the same data stays latched for several cycles. If this is true, then either the timing on the new parallel port is tighter, or the outputs are (more) current-limited. Can anyone verify this? 3 & 4 suggest a grounding problem. Might it help to tie all the signal grounds together on the Amiga end of the cable (pins 17-25), and/or tie together the signal and protective (frame) grounds at the printer end, since the computer doesn't have a separate frame ground? My next desperate attempt at a fix will be to shorten the cable as much as possible, unless someone can tell me what's REALLY wrong. I'm sorry if this sounds too much like a suicide threat 8^} I'll be eternally grateful to anyone who can help me out with this, excepting those who respond, 'Come on, get a printer that wasn't built during the Bronze Age.' ______________________________________________________________________________ /_____/_____/_____/_____/_____/_____/_____/_____/_____/_____/_____/_____/_____/ |_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|_____| _No dark sarcasm in the classroom|_____|_____|_____|_____|_____|_____|_____|___ |____Teachers leave the kids alone__|_____|_____|bryan@mothra.cs.utexas.edu___| ___|_____|_____|_____|___{ihnp4,seismo,...}!ut-sally!mothra.cs.utexas.edu!bryan |_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|_____|