mh 655 
necessary modifications include changes in the vertical or signal amplifier, 
increase in accelerating voltages, and modification of the deflecting—plate 
connections, The modifications of the amplifier circuit are: 
(1) the use of a low-impedance compensated step attenuator; 
(2) minor changes in frequency-compensation circuits; 
(3) redesigned position-control circuit; 
(4) decreased load resistance and direct plate to cathode-ray 
tube connections in the output stage. 
These changes were made to improve the frequency-response range under 
all conditions of gain and spot position, and to provide known gain set- 
tings which can be reproduced. The schematic circuit diagram is shown in 
Fige 5e 
Fine control of attenuation, without change in frequency response, is 
obtained by the use of a low-impedance voltage divider and a step switch 
which has very low stray capacitance. The amplifier response is further im- 
proved by the omission of a 0,005-pf condenser in the cathode of the first 
amplifier stage, the alteration of the vertical positioning circuit which 
reduces output impedance, and the redesign of the output stage to reduce 
load resistance and stray capacitance, Adjustment of the four compensating 
inductances requires care and understanding of the principles involved, 
Often turns must be taken from the output-stage inductances to reduce their 
valuee 
For use in recording transients, an eight-pin Jones plug permits patch- 
cord connection of the oscillograph to other control units, Single-sweep 
and beam-brightening voltages and control of cathode-ray spot position may 
thus be provided by external units, 
In the routine testing of this instrument, a check sheet is used and a 
test film is made to determine the performance of the oscillograph. The 
high-frequency response is first measured visually with a sine—wave input 
at the following frequencies: 10, 30, 100, 150, 200, 300, and 00 kc/sec. 
To be acceptable, the oscillograph must be flat within plus or minus 2 per- 
cent up to 300 kc/sec and show no rise at 00 kc/sec. The frequency-response 
curve of a typical instrument is shown in Fig. 6. -A photograph is then made 
to determine how well the oscilloscope will reproduce signals with an in- 
finitely sharp rise and exponential decay, Four signals are used with time 
constants corresponding to 50 msec, 150 psec, 500 psec, and infinite time 
