The museum found this Type 549 storage CRT production control card. These cards accompanied the CRT to aid in initial setup in the oscilloscope. This particular card was from Week 24, 1969. Although the fiscal year was June to May, week numbers followed the calendar year so week 24 would be in June 1969.
The 549 CRT design was focused on providing the highest stored writing speed achievable at that time. A new storage target structure was designed as well as a P-1 phosphor+MgO mixture with higher secondary emission ratio than the 564.
The “Enhanced Mode” allowed the writing speed to be increased at the expense of the Contrast Ratio. To support the 30 MHz capability of the mainframe, an “Integrate Mode” was added to allow high speed pulses with low repetition rate to be “summed” or integrated.
The fields are:
Upper Writing Limit: 250 volts
Writing Threshold: 220 V
Operating Range: 30 V (Difference needed for aging with time)
Operating Point: 235V (set the backplate voltage at this level for normal mode)
Ik (Flood Gun current): 23.5 mA
Enhanced Writing speed: 12 cm/microsecond (specification is >5)
Luminance measurements in foot lamberts (FL)
Written (Fade Positive) and ready-to-write (Background)
The contrast ratio is low because this is in the enhanced mode. In normal mode the contrast ratio specification is >4:1 and the writing speed specification is >0.5 cm/us