Storascope BLS-218

First: This device is extremely rare. As yet, only two examples of a Storascope are known to exist.

This is the forefather of the storage oscilloscopes (for example the HP 1703A or the Tektronix 549), or in other words, the screen version of a X/Y or Y/t plotter. It is designed to capture single or non-periodic events on a screen.

Contrary to conventional cathode ray or oscilloscope tubes, a Storascope contains a special blue print tube (here: Lorenz AS 17-21). A normal CRT has a luminescent coating on the inner front that is stimulated to illumination by a deflectable electron beam; this coating consists of special phosphore mixtures. Without electron beam there is no picture on the screen.

A blue print tube doesn't have a luminescent coating. Instead it has a calium chloride coating on a mica plate inside the tube. If the beam hits the coating the spot turns to a dark violet color. This coloring is permanent and can be removed by heating. This is accomplished by putting a relatively high current through the mica plate, which in turn gets hot and thus erases the screen. On the other hand it is possible to maintain the picture several month after turning off the device, depending on the temperature and light of the environment.

Picture of a damped oscillation

The same picture a bit bigger

You can see - unfortunately - some burns on the surface that are the result of some negligence. The manual contains several warnings about this...

Inner view of the power supply

The power supply of the Storascope is contained in a separate box that is attached with a hose thick cable to the main device. Among other things it includes the ballast for the luminescent lamp (to illuminate the screen), the black box at the front left in the picture, and the four power tubes PL36, normally known as horizontal output driver in TV sets, that are wired in parallel as linear regulator.

Some more impressions - without comment: