Path: utzoo!utgpu!attcan!uunet!husc6!ukma!nrl-cmf!ames!amelia!prandtl.nas.nasa.gov!msf From: msf@prandtl.nas.nasa.gov (Michael S. Fischbein) Newsgroups: comp.misc Subject: computer follies Summary: Killer tty Message-ID: <1065@amelia.nas.nasa.gov> Date: 27 Sep 88 19:22:41 GMT References: <5856@ihlpf.ATT.COM> <37600006@pyr1.cs.ucl.ac.uk> Sender: news@amelia.nas.nasa.gov Reply-To: msf@prandtl.nas.nasa.gov (Michael S. Fischbein) Organization: NASA Langley Research Center Lines: 36 I worked designing microprocessor based fire and security alarm systems for skyscrapers, back when microprocessors were a brand new idea. Well, we had development systems from two vendors and only one terminal. I came up with a cable to hook the ASR-33 up to the other development system so we didn't have to wait for that vendor to get a terminal to us. I carefully checked the connections, plugged the cable into the terminal and put a trusty VOM on the connections to make sure the signals were right. OK. Both off, connect the ASR-33 to the computer. Turn on the computer. Turn on the teletype. POP! Hissss... Yank both cords out of the power strip. Notice blue smoke coming out of the computer. Go back and measure the signals on the data connector with an O-scope. Gee, there's a 40 volt AC square wave superimposed on the TTL signal..... We tell the vendor of system 1 (that supplied the teletype) what's wrong with the teletype and ask for a replacement. No, that's the way it is supposed to work. Yep, sure it is. That's OK, they'll install it on their development system. They plug the teletype to their machine when it arrives. POP! Hisss... They take it to their local distribution center, the service engineer checks it out thoroughly, ``repairs'' it, hooks it up to one of their systems. POP! Hisss.... Two systems later, he admits mystification and ships the killer teletype back to the factory in California. Last I heard, the teletype had vaporized three systems back at the factory and they couldn't figure out what was wrong. mike Michael Fischbein msf@prandtl.nas.nasa.gov ...!seismo!decuac!csmunix!icase!msf These are my opinions and not necessarily official views of any organization.