Deep Thought Restoration Plan

This was a hobbyist style build by a young man so it is naturally a little rough around the edges. As changes were made holes were drilled and lights and switches were added and sometimes removed. The panels have some labels from a classic Dymo label machine. All of this adds to the character of the machine. I’d like to keep as much of that character as i can.

There are issues, though. Of course some of these are more important than others. They fall into four categories:

  • Safety
  • Functionality
  • Reliability / Maintainability
  • Cosmetic
Safety IssuesResolution
The power supply enclosure is too flimsy.Complete rebuild using 1.5mm aluminium sheet.
The wiring is not fused.Add fuse on 240V and on each DC rail consistent with DC wiring.
The fan in the computer enclosure runs from 240V and (a) the plug has live pins and (b) the chassis is not earthed.Replace 240V fan with 12V fan.
Several aluminium sheets have sharp edges where they have been cut or drilled.De-bur.

The functionality issues are generally minor:

Functional IssuesResolution
The video and tape connectors are on the front of the unit and the video connection is not the usual RCA.Add connectors on rear.
The parallel ports on the processor card and the I/O card are not accessible outside the enclosure (although the processor card parallel was exposed in an earlier state).Add 50 pin ribbon cable panel mounted connectors for each port.
The I/O card supports two parallel ports but only one parallel port MC6821 IC is fitted.Add the chip.
The power supply provides sense inputs for the 5V supply but they are not currently used.Add feedback lines from the computer terminal block. This will require a new power connector.
The keyboard does not work because the pads have deteriorated.Make new pads and fit.
Toggle switches seized.Replace.
No power light.Add lights to power unit and computer unit.
Reliability and Maintainability IssuesResolution
DC wiring has been done with mains flex. Colour coding is not great. Re-do with appropriate cable.
Several soldered connectors where IDC could be used.Replace.
Several wires soldered directly to processor board.Add connectors to prototype are and wire via those connectors.
Dry joints on several connectors.Reflow solder.
Cosmetic IssuesResolution
Aluminium finish oxidised and scratched.Work with scotchbrite.
Front panel cutouts are too rough. Square off.
Missing and corroded fasteners.Replace.
Rear and right panels have large unused holes.Replace panels.
Lid not properly fixed and too light.Replace with 5mm perspex – strong and allows the interior to be enjoyed.
Processor board wiring. The mods are a little “in your face”. Re-wire a little more subtly.

This adds up to a lot of work!

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