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Specifications

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CA1 Course Notes
Sharp Electronics (UK) Limited
CE Technical Support GroupPage 50
CA1 Power Supply
The power supply used in the CA1 chassis is very similar to that used in the CA10, except that its current
suppling characteristics are lower and it does not turn off while the receiver is in standby. Therefore IC702
is not fitted and the power consumption of this receiver will be higher than that of the CA10, at approximately
9.5W. Note that on the actual circuit, some of the component references will be different, but the circuit
configuration and operation remains the same. Please refer to the beginning of these notes for more
information.
The following voltages are generated by the chopper stage. Note that the +5Va line is always present and
that the +105V supply is regulated in standby, i.e. it will measure +105V in standby.
Stand by Voltage Running Voltage Resistance to Ground Generation Point
+20.1V +20.3V =<100k D719 cathode, Pin 16 of T700
+105.8V +104.3V =<80k D708 cathode, Pin 11 of T700
+9.4V +9,8V =<100k D709 cathode, Pin 12 of T700
-11.3V -11.6V =<100k D710 anode, Pin 14 of T700
+7.0V +7.1V =<20k D712 cathode, Pin 9 of T700
0V +5.1V 1.4k Q708 emitter
+5.1V +5.1V Approx 500R Q704 emitter
As the load on the power supply is increased, the frequency of operation will decrease, conversely, as the
load on the power supply decreases, the frequency of operation increases. While in the running mode, the
frequency of operation is approximately 100kHz, which is obviously dependent on a number of factors, the
main ones being beam current and volume setting. Whilst in standby the frequency is about 160kHz.
Regulation Control Circuit
As mentioned previously, the basic construction and operation of the power supply circuit is similar to that
of the CA10 chassis. However, the major difference is the voltage fed back circuit which is shown in the
diagram below.
Figure 43 : CA1 Voltage Regulation Feed Back Circuit
It can be seen that the +105V supply is monitored using a potential divider network that feeds straight into