Once apart for repair in June 2024 I took these photos with my phone.
Click each image for a high resolution view.
The old pH probe swings into a shielded metal box for shielding. It's lovely old lab gear quality.
The chassis is bent brass sheet (brass is very easy to work). Wiring is old-fashioneed point to point, laced,
as required by the device components. The Model 01 Control Engine
was a board I made for embedding in projects like this; a small CPU with many inputs and outputs and power.
The main display device are these lovely but noisy and difficult to use "digital display units", they probably have a more common industry name. They were once popular in train stations for announcements. 1960's desk clocks used them. These are "addressable", there's a 12-pole rotary switch that tells code where it is and the motor is run until that symbol is displayed. The motors are 110VAC and the switches unreliable.
These IEE "one plane" display (a direct reference to Nixie tubes' worst feature: stacked digits) are bluntly straightforward; twelve little projectors with masks lenses and lamps, lit (presumably) one at a time. Each projects onto the backside of a frosted plastic sheet.
