TELE-TECH & - AmericanRadioHistory.Com

i
fGqfq
0/
100
NOE TUBES5
NO.OF OF TURES503
x7
?
90
80
:461
i4
3
V.3
2
i ND
/r
LIFE INDURS) 1000
OF TUBES 364
I
TYPE 5654/6465-W/6096
CONDITIONS
TEST LIFE
HEATER VOLTS
63 6.3
PLATE VOLTS
120 ISO
T GRID NO I VOLTS 2 0-
GRID N0.2 VOLTS
120 125
CATHODE RESISTOR
(OHMS)
1.30
-r GRID RESISTOR
MEGOHMS)
NO
0.1
HEATER -CATHODE VOLTS
135 -
BULB TEMPERATURE (.C) 165
NE (HOURS))= 500
NO OF TUBES 503
M
O0
90
BO
70
R 6°
á
2
g 4°
1130
20
TYPE 5654/651(5-W/6096
TEST LIFE
CONDITIONS
HEATER VOLTS 6,3
PLATE VOLTS 120
GRID NOI VOLTS -2
GRID NO2 VOLTS 120
CATHODE RE-
SISTOR (OHMS)
RESIS-
TOR (MEGOHMS)
HEATER CATH-
ODE VOLTS
BULB TEMPERAT-
URE COI
I
LIFE (HOURS) 1000
NO. OF TUBES .139
LIFE
LIFE
150
0
125
130
O1
135
165
LIFE IHDURSI . 0
NO OF TUBES 180
LIFE (HOURS) 500 -
NO OFPF TUBES 166
LIFE (HOURS) 0
NO OF TUBES IRO
(HOURS) 500
NO OF TUBES 1667
I /
i+
a
D
LIFE (HOURS)
NO OF TUBES
90 465 ..
'so
550
3 40
3
20
- - (MEGOHMS)
LIFE (HOURS(. 1000
NO OF TUBES 52
LIFE (HOURS) 5000
NO OF TUBES.61
1-
LIFE (HOURS) . 2000
NO OF TUBES 69
LIFE (HOURS( 4000
"N0. 0 TUBEES.45
LIFE (HOURS) . 3000
N0. 0 IUBES 67
TYPE 5718
CONDITIONS
HEATER VOLTS
PLATE VOLTS
iGRID VOLTS
CATHODE RESISTOR
GR 1 rRMESSiSTOR
HEATER CATHODE VOLTS
BULB TEMPERATURE (C)
EST
63
IVO
ISO
IFE
6.3
100
150
10 -
200
220
LIFE (HO (PSI -'DOD
-NO
10
10 20 30 40
CHANGE IN 7RANSCONDUCTANCE - %
Fig. 1: Type 5654/6AK5- change in G.
10 12 14
PLATE MILLIAMPERES
Fig. 2: Type 5654/6AK5 -for values of I,
60
CHANGE DIN TRANSCONDUCTANCEO- %
Fig. 3: Type 5718- changes in G.
70
Tube -Characteristic Changes
And Equipment Reliability
By The Applications Engineers of the
Advisory Group on Electron Tubes
EQUIPMENT reliability usually
denotes the degree of assurance
that the equipment will satisfactorily
perform its intended purpose
for the time required. Because
any changes in component performance
can seriously affect this reliability,
it is important that the
equipment designer carefully consider
the extent of changes in electron
-tube characteristics which may
occur during extended periods of
operation in his circuit design.
Ideally, the circuit designer
should know exactly how much
change in tube characteristics will
occur under the specific operating
conditions of the equipment. The
realization of this ideal is usually
precluded by two very important
considerations:
1. The exact electrical, mechanical,
and thermal environments of
any given application are either not
known or are so complex that exact
duplication is virtually impossible.
THE ADVISORY GROUP ON ELECTRON
TUBES, 346 Broadway, N. Y. 13, N. Y.
2. The probable change of characteristics
for the tubes to be used
must be estimated from the results
obtained from a small sample life -
tested under given conditions.
Estimating Performance
Although it is not the intent to
imply that a sampling procedure
for acceptance testing is improper,
the designer should consider the
limitations of such testing. Life
testing of a sample can only reveal
the performance of the individuals
in the sample under the specific conditions
of operation, and provide an
estimate of the probable performance
of the individuals remaining
in the lot. The ideal from the standpoint
of "reliability design" would
be to test all electron tubes to destruction
under conditions identical
to those encountered in the actual
equipment. The information thus
obtained would reveal exactly what
reliability would have been achieved
in the equipment. It is evident,
however, that under such conditions
no electron tubes would be available
for use in the equipment. Conse-
quently, sample testing and probable
lot compliance provide the only
practical approach for establishing
a premise for determining equipment
reliability.
Data similar to those included in
this article can be used to estimate
the performance reliability of
equipments, but cannot be used to
assure such reliability. Because individual
electron tubes procured
may meet just the minimum requirements
of the procurement
specification, the data shown here
may be optimistic.
All electron tubes do not change
at the same rate, even if they are
from the same production lot. Consequently,
the data revealed from
life testing must be presented in
some form which shows the probability
of occurrence. The form
chosen for this article is the "ogive"
or cumulative frequency distribution,
in which ordinate values are
equal to percentages below (or
above) the abscissa values. These
ordinates can also be considered as
measures of the probability of occurrence.
The confidence with which
96
Tele -Tech & ELECTRONIC INDUSTRIES June 1956