Henry Radio 3K Classic Mark II Operating And Maintenance Manual page 37

RANGE VALUES FOR EQUIPMENT DESIGN Min
Max
Fi!amcnt Current at 7.5V ............................................................... 20.0 22.7
Aac
Direct Intere!ectrode Capacitance ( grounded grid connection)
Input . . . .. ..... . ... . . .. . . . . ... ............ .. ............ .. ..... .. .... .. .. .. . .. . . ... . . . 18.5 22.5 pF
Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 11.8 pF
Feedback
- 0.9 pF
Direct Interelectrode Capacitance ( grounded cathode connection)
Input .. . . .. . .. . . ... .. .. . .. .... ...... .. ....... .. .. ...... .... ... ...... . . ... . . . . .. . . .. . . .
18.5
22.5
pF
Output ... ............................................................................ 0.9 pF
Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.8 11.8 pF
APPLICATION
MECHANICAL
MOUNTING- The 3CX1200A7 must be operated
vertically. base tip or down. A flexible connecting strap
should be provided between plate connector and
oxternai plate circuit. The tube must be protected from
severe vibration and shock.
SOCKET The EIMAC SK-410 air system socket and
SK-4:36 -:himney are recommended for use with the
3CX1 200A7 When a socket other than the SK-410 is
used. provisions must be made for equivalent cooling
of the base. the envelope. and the plate lead.
HOT SURFACES: When the tube is used in air and air
cooled, external surfaces may reach temperatures up
to 200 degrees C and higher. In addition to the anode,
the cathode insulator and cathode-heater surfaces
especially may reach the high temperatures. All hot
surfaces may remain hot for an extended time after the
tube is shut oft. To prevent serious burns, take care to
avoid any bodily contact with these surfaces, both
during. and for a reasonable cool-down period after.
tube operation.
if a socket other than the EIMAC SK-410 is used, the
user should assure himself that strong !ateral pressure
:s not applied to the tube base pins Otherwise, even
though the base of the tube is reinforced, damage to
he base seals may result.
COOLING-
Forced-air cooling is required to maintain
the base; seals at a temperature below 250° C. and the
Plate seal at a temperature below 250° C. Air flow
requirements to maintain the above maximum temper-
. . itures are shown @n cooling data curve.
At 1200 W of plate dissipation an airflow of 30 ctm with
a back prnssl.ir(.-z of 0.5 inches of water should be
apt;'A,;d and directed through the fins of the tube A
Min-rnur;i of 5 cfm must be supplied to the base of tube
whenover thofilament voltage is on.
in all cases. the only criterion of proper cooling is the
tenit.;uraVc; of the tube seals. Tube temperatures may
he ifl(?aSlireci with temperature sensitive paint, spray,
c)r c;rayrm
ELECTRICAL
ABSOLUTE MAXIMUM RATINGS: Values shown for
each type of service are based on the "absolute
system" and are not to be exceeded under any service
conditions. These ratings are limiting values outside
which the serviceability of the tube may be impaired. In
order not to exceed absolute ratings. the equipment
designer has the responsibility of determining an
average design va!ue for each rating below the
absolute value of that rating by a safety factor so that
the absolute values will never be exceeded under any
usual conditions of supply voltage variation in the
equipment itself. It does not necessarily follow that
combinations of absolute maximum ratings can be
attained simultaneously.
ZERO-BIAS OPERATION:
Operation at zuro-bias is
not recornmended with plate voltages over 4000 since,
plate dissipation may be exceeded. A rener diode
placing positive bias on the cathode or other constant
voltage source may be used to reduce zero signal
plate current at plate potentials over 4000 volts.
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