A Short Story about Network Interference

It was 1989ish at The Voyager Company in Santa Monica. Amongst my duties was ad-hoc network admin. We had a LocalTalk network that ran over telephone wire, across several floors, using PhoneNet connectors at each Macintosh, and meeting in a closet at a Star repeater.

One day the employees started to notice that printing to our Laserwriters was slow. Accessing our file server was slow. Email was slow. I checked things out, rebooted printers and servers, and nothing fixed it. I worked all day trying to isolate things to no avail.

Then, all of a sudden around 6pm things began to work properly again. I wasn’t sure what I, or someone else, had done but it was working so I went home.

The next morning I arrived early and things were still working so I went about my day working on Beethoven’s Ninth Symphony CD-ROM (DEMO). Around 11am, people started to complain that the network was down again. I checked the server and indeed, it was extremely sluggish.

I spent some more time and once again, I had no fix. I worked late, checking wiring in the closet for evidence of rodents, etc and just like the day before the network magically repaired itself.

Ok, I’m a young software programmer and I am pretty good at debugging software, but this hardware was starting to make me mad. Once again I went home not knowing what fixed it.

The following morning, now day three of this mysterious issue, I was again at work early but this time I was upstairs on my computer. My friend Simeon came into the office and sat down with his computer that he brought from home. He started to work and just then I saw the printers disappear from my Chooser.

Wait a minute.

“Simeon, do you bring your computer from home every day?” Simeon had a Mac Pro or SE, I cannot remember exactly, but it was the form of the original luggable. As I asked the question, I walked over to him and as he answered something like “yeah” I saw it and I knew what the issue was.

I reached around his Mac, disconnected the PhoneNet connector and mmediately the network came back to life.

What was the clue that I saw?

A wavy left side of the Macintosh screen, indicative of a bad flyback transformer. I had had this same issue on my original Mac 128k so I knew what to look for.

That darned bad transformer was spewing garbage which was interfering with the PhoneNet connector in some manner. Because LocalTalk was a chained network, all data travelled around the network and one bad connector took down the entire thing.