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Model 5065A
Circuit Diagrams, Theory, and Maintenance
A2 BATTERY CHARGER ASSEMBLY THEORY
CHARGING CURRENT REGULATOR CIRCUIT
The charging current regulator is made up of A2CR7,
A2Q5, Q6, and Q4. Ac voltage from T1 is applied to
A2(10, 11) and rectified by bridge network A2CR1 to
A2CR4. Voltage regulation occurs through A2Q5 and
Q4. A2Q6 monitors battery charging current by sensing
the voltage drop across A2R12 and A2R13.
Increases
in battery charging current are sensed by A2Q6 which
conducts and increases voltage drop across A2R7.
The decrease in bias at A2Q5 base regulates the
charging current from Q4 to within limits set by A2CR7.
In the FLOAT position of S6, the battery receives a
trickle-charge. When S6 is in FAST position A2R12 is
bypassed which increases the charging current to the
battery.
BATTERY LAMP CONTROL CIRCUIT
The battery lamp control circuit is comprised of A2Q1,
Q2, Q3, Q4, and A2CR6, CR8. In the FLOAT position,
BATTERY lamp DS3 is off.
Multivibrator A2Q1, Q3 is
off and A2Q2 is biased off. When the ac line is inter
rupted, a voltage signal from the Battery Cut-in Circuit
turns on A2Q7 and Q2, and triggers the multivibrator
A2Q1, Q3. This causes the BATTERY lamp to flash on
and off.
Operating voltage comes from the battery
through Q14 to the Power Supply and Regulator A15.
The lamp will continue to flash until the ac power is
restored and RESET is pressed. In RESET position CR8
gate element is grounded turning CR8, Q2, the multi
vibrator circuit, and the lamp off. In the FAST CHARGE
position S6 shorts out A2R12 and increases the battery
charging current. Another section of S6 also provides a
ground for the battery lamp through A2R6 to turn the
lamp on continously.
BATTERY CUT-IN CIRCUIT
The battery cut-in circuit is made up of A2CR9, Q8, Q9,
Q12, and Q15-
The dc voltage from the instrument
power supply is monitored through CR9. As long as the
dc voltage is present Q8 conducts and Q9 is cut off.
When ac power is interrupted, Q8 is turned off and Q9
is turned on. This turns Q12, Q15, and Q13 on. This
action also turns on the dc power switch Q14 and
sustains instrument operation from the battery.
BATTERY DISCONNECT CIRCUIT
The Battery Disconnect Circuit consists of A2CR11,
Q10, Q11, K1, and CR15.
During battery operation,
battery voltage monitored through CR11 keeps Q10
turned on.
When the battery voltage decreases to
approximately 23 volts, Q10 turns off and causes Q11 to
turn on.
This in turn energizes differential relay K1,
and disconnects the battery.
When ac power is re-
applied, Q10 again conducts. This reverses the polarity
of A2K1 and reconnects the battery.
8-20
OPERATIONAL CHECK
a. Observe
the
CIRCUIT
CHECK
BATTERY
position; indication should be between 30 and 50.
b.
Disconnect ac cord from ac line; BATTERY
lamp should flash on and off. RESET has no effect.
c.
Connect ac power cord to ac line.
RESET
BATTERY switch; BATTERY lamp should stop flashing.
Set BATTERY switch to FAST CHARGE; BATTERY lamp
_
should light.
Return switch to FLOAT position and
BATTERY lamp will go out.
This completes the check.
TROUBLESHOOTING
—
NOTE
These tests check individual circuits on
Battery Charger Assembly A2.
If failure is
indicated in a circuit, repair the circuit and
perform battery charger operational check.
a.
Charging Current Regulator.
1.
Charging current to the battery should be:
_
FLOAT: 12 to 34 mA (see Paragraph 5-35)
FAST CHARGE: 90 to 150 mA (see Paragraph 5-35)
2.
If the current
differs
substantially
check
A2CR1 to CR4 for power rectification and
CR7 for indicated voltage. Check Q4, A2Q5,
A2Q6 operation. Check S6.
—
b.
Battery Lamp Control.
1.
If the lamp does not flash when ac is inter
rupted, check
Q1, Q3 multivibrator,
and
check that collector of A2Q2 is below 1 volt.
2.
If the lamp does not light with switch S6 in
FAST CHARGE check S6 and DS3 or R6.
3.
If Battery lamp won't light, check lamp DS3
—
and S6. If it won't go out, manually ground
the + gate element of CR8. If the lamp goes
out, check S6, otherwise, check CR8, Q2,
Q1,andQ3.
—
c.
Battery Cut-in Circuit.
_
1.
Disconnect ac power cord from ac power
source. Instrument should switch to Battery
Operation and DS3 should flash on and
_
off.
If this does not occur, check that col
lector A2Q12 increases from approximately
10 volts to 20 volts.
If not check Zener
voltages of A2CR9 and replace if it is outside —
the 10 to 12 volt range. Replace A2Q8, 9 and
12 successively in that order.
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