Section I11
Paragraphs 3-16 to 3-27
Model 204B
3
-
16,
RECHARGING NICKEL- CADMIUM
BATTERIES.
3-17. The batteries should be considered
as
fully
discharged when maximum oscillator output drops
below
5.0
volts rms opencircuit
or
less than
2.
5 volts
rms into 600 ohms. The batteries
will
not operate
much longer when this point
is
reached and the osci-
llator probably will not meet specifications. Exces-
sive discharge of batteries may damage them
or
shorten their life.
3-18. To recharge batteries, turn oscillator OFF and
connect power cord to
a
suitable power source.
The
batteries will be fully charged in approximately
60
hours at
a
5.5 miliiampere charge current and
30
hours at
a
11
milliampere charge current
if
they were
fully discharged
at
the beginning. The instrument can
be turned on for use after an initial charge of
at
least
20 minutes.
If
the batteries
were
only partiallydis-
charged, the oscillator can be turned on for use
at
any
time. The charge
rate
is
the same whether the osci-
llator
is
OFF
or
operating; therefore, very little in-
crease in charging time will be required
if
the instru-
ment
is
used while the batteries are being recharged
The charge circuit can be increased with the charge
current adjustment R102 (refer to figure 5-11) to
a
maximum of
11
milliamperes to provide
a
quick
charge. The
11
milliampere charge rate should be
used for quick charge only. Repeated chargingat
a
high rate
will
shorten battery life.
3-19. The batterJes can beocharged
at
ang tempera-
ture between +32
F
to +122
F
(0
C to +50 C). How-
ever, to obtain optimum battery life, recharging
should be tone
at
a
temperature of 80.6'F
*lO°F
(27OC *5.6 C).
CAUTION
THE FOUR NICKEL-CADMIUM BATTERIES
ARE HERMETICALLY SEALED AND CAN BE
DAMAGED IF CHARGED AT A FAST RATE
AT
A
TEMPERATURE EXCEEDING
122
F
(5OOC). IF THE CHARGE CURRENT ADJUST-
MENT
HAS
BEEN SET FORA QUICK CHARGE
RATE, PLACE THE INSTRUMENT
IN
A
LOCATION WHERE THE AMBIEYT
TEMPERATURE DOES NOT EXCEED 104
F
(4OOC).
3-20. CYCLE-LIFE OF NICKEL-CADMIUM
BATTERIES,
3-21. As extremes in temperatures are approached,
the cycle-life (complete charge-discharge cycles) of
the batteries
is
reduced. Storage at high tempera-
tures
will
increase the self-discharge rate and also
decrease the cycle-life. Permanent battery damage
may result
if
the batteries are stored
at
a
high tem-
perature for
a
prolonged period.
3-22. Battery cycle-life canbe extended by recharg-
ing before the batteries are completely discharged,
charging and discharging at
a
rate which
is
slower
than the maximum ten-hour rate specified by the
manufacturer, and by not overcharging.
3-23. The cycle-life of the batteries is based, by
the manufacturerer,on
an
endpoint
of
80% of the rated
225 milliampere-hour capacity. This
is
with
a
ten-
hour charge and discharge current of
22.
5 milliam-
peres with discharge carried to the normal ten-hour
end voltage (1.10 volts/cell x
5
=
5.50 volts/battery)
on every cycle. Under these conditions
a
cycle-life
in excess
of
100
cycles can be expected.
3-24. When used topowerthe
@
Model 204BOscilla-
tor, the batteries are discharged at approximately
a
40 hour
rate.
The batteries are not fully discharged
if
they
are
recharged
as
recommended in paragraph
3-25. Optimum battery life can be obtained by fol-
lowing
a
simple routine of
1)
preventing complete
battery discharge by recharging before the oscillator
output level drops below 5.0 V rms into an open cir-
cuit
(2.
5 V rms into 600 ohms),
2)
keeping the use of
a
quick charge to
a
minimum, 3) operati.i,r at mod-
erate
temperatures whenever possible and 4) by dis-
connecting power cord after 60 hours of continuous
charging with oscillator turned OFF (30 hours
if
charging batteries at
a
quick charge rate).
3-26.
MERCURY BATTERY REPLACEMENT.
3-27. Battery replacement
is
required
wnen
the
oscillator output becomes less than
5.0
volts rms open
circuit
or
less than
2.
5volts rms into 600 ohms pro-
vided the DC BAL
is
adjusted correctly. Replace the
batteries with four 6. 75-volt mercury batteries
(Mallory type TR235R
or
equivalent). Refer to figure
3-2, and proceed
as
follows:
a.
Remove top cover retaining screw and slide
cover from instrument.
b.
Remove wing nuts and battery clamps.
c. Remove and dispose of batteries according to
paragraph 1-6.
d. Install replacement batteries
so
that battery
polarity matches polarity designation on battery
clamps.
e.
f.
Replace top cover.
3-16.
Replace battery clamps and wing nuts.
POLARITY
DES IGN-ATION
WING
N
UT
2046-S-I
I
BATTERY
CLAMP
Figure 3-2. Rear View of Model 204B Showing
Mercury Batteries Installed.
3-2
01369-2
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