PrintStar's Blog
Ramblings of a Fortran Nut
October 26, 2016 by Jeff

Troubleshooting Some Hardware Issues

Today I wanted to set up my Rainbow 100 server, but I ran into some unforeseen issues.  After spending far too long trying to find the “perfect” combination of serial cables, null modem adapters, and gender changers, I decided I better actually turn on the Rainbow I’ll be configuring as a floppy-driven web server.  That’s when I ran into problems.

My web server is a Rainbow 100A variant, meaning it:

  • can’t boot directly from a hard disk (a.k.a. a Winchester disk)
  • supports less RAM
  • has an older BIOS

All these things really don’t matter for this application except, perhaps, the RAM.

After connecting the monitor and powering it up, I was presented with a blank screen and 8 illuminated diagnostic LEDs on the back panel.  It appeared dead.  Pulling the motherboard and removing the memory expansion did not alleviate the symptoms.  Swapping the floppy controller also didn’t help matters.

When Rainbow motherboards aren’t working, I usually move on quickly.  I still have some spares, and trying to diagnose why it isn’t working can be tedious.  I had exactly one spare Rainbow 100A motherboard, and I swapped it into the machine.  The system posted, but the RX50 floppy drive was dead (and one of the “B” drive door pins was missing).  Swapping the floppy drive and exercising it a bit yielded a working system.

Time for some pictures!  The server internals:

The delightfully large amount of space DEC left for cabling the drives to the controllers and power supply to the motherboard can be extremely frustrating:

A closeup of the labeling of a relatively rare Suitable Solutions IDrive, which provides a double-sided double-density IBM-compatible floppy drive on a Rainbow:

After checking out this machine, I’ve slid it back into its tower stand in preparation for its service as a web server.

As a side task, I need to back up the floppy that came with this box.  I’m not sure that the IDrive drivers are generally available anywhere anymore.

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