Ericsson GE 19B801507P1, Maintenance Manual

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As the battery pack temperature increases to 10°C above
ambient at end of charge, the voltages at A13-13 and A13-14
become equal, indicating the bridge circuit is balanced and the
battery pack is fully charged. A14-6 goes low, causing Q4 to
stop conducting. Q3 cuts off and the charge rate switches from
the high charge rate to the trickle charge rate . The equal volt-
ages on A13-13 and A13-14 cause the output at A13-10 to go
high, turning READY indicator DS2 on.
A memory circuit internal to A13 is set so that the same
battery can not be recharged at the high rate unless it first has
been discharged or removed from the charger. When the bat-
tery pack is removed from the charging insert, RT (BATT) is
removed from the bridge circuit causing the bridge to again be
unbalanced. A13 senses the bridge in an unbalanced state, the
voltage A13-13 being larger than the voltage on A13-14, and
resets the charger memory. Microswitch S1 will also remove
power from the charger circuits, causing the memory to reset.
Voltage Controlled Cut Off
The voltage controlled cut off circuit monitors the battery
voltage and cuts off regulator Q3 when the battery charging
terminal voltage exceeds 9.5 Vdc. It is comprised of Compara-
tor A7, Charge Control IC A13, and associated circuitry.
A reference voltage derived from voltage divider R37, R38,
R41, and zener diode CR12 is applied to pin 2 of Op-Amp A7.
Resistor R43 is adjusted for a battery charging terminal voltage
of 9.5 Vdc. A voltage equal to the reference voltage on pin 2 is
applied to pin 3 of A7. This causes A7-1 to go high, applying a
lesser voltage to A13-14 than is applied to A13-13. This causes
A13 to turn Q3 off and turn READY indicator DS2 on.
Power Input And 8 Volt Regulator
A positive 13.8 Vdc from the vehicle battery is supplied to
the Charger board through a 5 ampere fuse and J1-6. Diode
CR14 provides reverse voltage polarity protection. Voltage
regulator A1 regulates the vehicle input battery voltage (13.8
Vdc) down to +8.0 Vdc and supplies it to the circuitry in the
personal radio while the battery in the personal radio is being
charged.
When a radio is inserted into the charger, radio detect mi-
croswitch S1 closes and applies 13.8 Vdc to charging control
circuit A13 through a line filter consisting of C1, C2, C7, and
L1. 13.8 Vdc is also applied through J7-4, VOLUME control
on-off switch S11, J7-5, J9-1, RADIO ENGAGED (latch)
switch S3 to Comparator A5, audio amplifier A12 and to 8 volt
regulator A1.
Input voltage to regulator A1 is applied to pins 11 and 12.
The output of A1 controls the base of NPN pass transistor Q1,
causing it to increase or decrease conduction as required by the
load. Q1 functions as a variable resistor. The regulated output
voltage is set to 8.0 Vdc by variable resistor R5. TP1 provides
a convenient place to monitor the 8.0 Vdc output of regulator
A1. The regulated 8.0 Vdc output is applied directly to the ra-
dio, or through contacts 3 and 4 of K2 and to the battery charg-
ing terminal. K2 is controlled by the microphone PTT switch
through inverter A3 and is energized when the PTT switch is
operated. K2 allows operation of the radio even though the bat-
tery may be dead.
Audio Amplifier A12 (12 Watts)
Audio amplifier A12 is an integrated circuit used to amplify
receive audio from the radio to a level of 12 watts. The ampli-
fied audio is then applied to a 15-watt, 4-ohm speaker through
J1-4 &5.
Receive audio (audio out) from the radio is applied to the
input of audio amplifier, A12-10, through the UDC connector
and cable assembly CA1 and J6-6 on the Charger board, con-
tacts 8 & 9 on analog switch A9, and volume control/ on-off
switch VR1/S11. The speaker is connected through P1 to J1.
The audio input level from the radio is controlled by volume
control/on-off switch VR1/S11.
A12 contains internal protection circuitry to safeguard
against line surges, thermal overloads, and speaker shorts to
ground. Input voltage (13.8 Vdc) from the battery is applied to
A12-6.
External Microphone
The external microphone circuit consists of buffer/amplifier
A5 and Q5, audio delay circuit Q6, analog switch A9, and PTT
inverter/buffer A3.
Audio Delay
Prior to operating the PTT switch, audio delay transistor
Q6 is turned on and Capacitor C65 charged through CR15 and
R54 (13.8 Vdc). During this time Q6 and closed contacts A9-3
& 5 and 8 & 9 apply ground to the receive audio line from the
radio and the external mic audio line to prevent any unwanted
audio from entering the 12 - watt audio amplifier.
Figure 4 - Vehicular Charger W/12 Watt Amplifier
During charging there is one diode drop between the
(+) charge terminal and the (+) terminal of the bat-
tery pack.
NOTE
LBI-31864
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