665 
stb, 
The low-voltage supply (sec Fig. 12) is a conventional regulated power 
supply of the cathode-follower type. Of interest, however, is the divider 
network supplying the sercen of the 6SJ7 amplifier tube. This allows the 
screen to work at a respectable voltage and still supply perfect compensa- 
tion for input voltage fluctuations, The use of Amperite ballast tubes to 
regulate the heaters of the amplifier tubes is a great improvement. Even 
more improvement can be obtained by increasing the working voltage drop 
across the Amperites by the use of a transformer rated for higher output 
voltagee A regulated negative supply delivers 1000-volt accelerating poten- 
tial to the cathode-ray tube circuits. The ciréuit is similar to that 
described in Sec. 2(b) and shown in Fig. 13, except that a half-wave rectifier 
without doubling is used, The other half wave from the supply transformer 
is used as power source of a 1700=-volt positive supply for the cathode-ray 
tube intensifier electrodes, This is a conventional half-wave supply with 
type 2X2 rectifier and condenser input filter, 
The camera unit consists of a hood which is bolted to the front of the 
relay ratky This hood has fittings so that either a General Radio oscillo= 
graph camera or a rotating—drum camera (see Part III) may be used, 
(2) Testing of oscillograph, The unit is tested in essentially the 
manner described in Secs 1(d). However, much more care is necessary in the 
checking for base-line drift. This is usually caused by a difference in the 
characteristics of the first amplifier tubes (6SH7). 
One unit has been in use for six months and has given very satisfactory 
SeErvicee 
2. Cathode-ray tubes and supplies 
The requirements imposed on cathode-ray tubes used for recording tran= 
Sients are more stringent than when the tubes are used for observation of 
stationary patterns, particularly when high writing speeds are neededy In 
the first place, higher accelerating voltages are required to give a sharper, 
more intense spotw~ Second, a means must usually be provided for modulating 
the spot intensity. The intensity=control grid is usually operated at a 
high negative potential, which makes necessary a coupling device from the 
brightener circuit [see Sec. 2(c)], and in addition, it is important to avoid 
undesired modulation of the intensity by 60-cycle or other pickup. A third 
consideration is the fact that the deflection fuictor of the tube (voltage 
