The Case Of The Vintage Computer, The Blown Fuse, And The Diode

If you are the operator of a vintage computer, probably the only one of its type remaining in service, probably the worst thing you can hear is a loud pop followed by your machine abruptly powering down. That’s what happened to the Elliott 803B in the UK’s National Museum Of Computing, and its maintainer [Peter Onion] has written an account of his getting it back online.

The Elliott is a large machine from the early 1960s, and because mains supplies in those days could be unreliable it has a rudimentary UPS to keep it going during a brownout. A hefty Ni-Cd battery is permanently hooked up to a charger that also serves as the power supply for the machine, ensuring that it can continue to operate for a short while as the voltage drops. A spate of fuses had blown in this power supply, so we’re taken through the process of fault-finding. Eventually the failure is found in a rectifier diode, the closest modern equivalent is substituted, and after testing the machine comes back to life.

We’re used to reading these stories from the other side of the Atlantic, so we welcome TNMOC saying that this is the first of a series of technical posts on their work. We visited the museum back in 2016, and also featured its famous recreated Colossus.

7 thoughts on “The Case Of The Vintage Computer, The Blown Fuse, And The Diode

    1. Those early computers were usually housed in special dust-free rooms and certainly not in some dusty and/or smoky office. In the early 60’s my late father designed several buildings with a clean computer room. He used to joke that this one room was as expensive as the rest of the building.

  1. I cut my computer teeth on an Elliott 803B which was donated to King’s School Gloucester UK in the late 1970s. Fond memories of ticker tape whizzing past blinken lights after school. It took 20+ mins simply to copy a file (load copy program paper reel, load source reel, punch blank copy reel), just getting it to work was worth celebrating. When I tell today’s pupils that computers once had no screens I get looks of sheer disbelief. It was supplimented with Tandy TRS 80s not long after (they had screens but lacked the mechanical allure). I wonder what happened to it – I’d like to think it could be Bletchley Park’s one…

  2. TNMOC used to have a series of articles describing progress of the various projects. They tailed off then eventually stopped appearing, suggesting that they were all written by a single volunteer who was unable to continue. They are much missed.

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