Ken Shirriff's Reverse Engineering Enters the Third Dimension with a Apollo Component's CT Scan
Using a high-end CT scanner with handy web interface, Shirriff's latest reverse engineering adventure peers into the unknown.
Noted engineer and vintage electronics enthusiast Ken Shirriff has turned to a new tool for his latest vintage component reverse engineering endeavor: a three-dimensional compute tomography (CT) scan, providing an incredibly detailed view of its inner workings without the need to take it apart.
"How can you find out what's inside a sealed electronics module from the 1960s, [like this] encapsulated flip flop module that was used for ground-testing of equipment from the Apollo space program" Shirriff asks. "Last month, I reverse engineered a simpler Motorola module using 2D X-rays. However, this flip flop module was much more complex and I couldn't reverse engineer it from standard X-rays."
The solution: Taking the problem into the third dimension, thanks to an imaging company called Lumafield and its Neptune Computed Tomography (CT) scanner. "You put an item on the turntable and the unit automatically takes X-rays from hundreds of different angles," Shirriff explains. "Cloud software then generates a 3D representation from the X-rays."
With the cloud data captured, Shirriff was able to use software to view the part's internals from any angle using a simple web-based interface — or create sliced cross-sections to look deeper inside a given part. Using this, Shirriff identified two NPN transistors, carbon composition and film resistors — which show up as metal pins with an invisible gap between, the carbon allowing the X-rays to pass through unhindered, or metal end-caps with another gap for the film version — diodes, and capacitors.
By adjusting the visualization, Shirriff further retrieved top- and bottom-layer wiring from the cordwood-layout part — providing everything needed to reverse engineer the circuit and produce a schematic for a part, used in the Up-Data Link Confidence Test Set tool for the Apollo missions, which has previously been something of a mystery.
Shirriff's full write-up is available on his website alongside linked to the reverse engineering efforts of other Apollo components; the CT scan of the component is available on the Lumafield website following free account registration.