Specifications

CA10 Course Notes
Sharp Electronics (UK) Limited
CE Technical Support GroupPage 4
This self running switched mode power supply is based around a single field effect transistor, Q701 and
generates the following supplies for use in various parts of the receiver. Note that other supplies are
generated by the line stage and are covered in the Line Stage section of these notes.
Supply Purpose Point of Generation
+18V Audio and frame output amplifiers D718, pin 8 of T701
-18V Audio and frame output amplifiers D719, pin 8 of T701
+150V Line output, CRT drive amplifier and VT line D720, Pin 4 of T701
generation
+13V Source of +8V supply D711, pin 5of T701
+8V IC201 supply IC706
+7V Source of STB5V and 5V D722, pin 1 of T701
STB5V Supply for IC101/2/5/6 Q706
+5V Supply for IC305, tuner Q707
Note : The voltages attributed to the rails on the circuit are not necessarily the measured voltage. See
the Power supply voltage line resistances to earth section of these notes for actual measured
voltages and nominal cold resistances to ground.
Mains input circuit
Figure 2 : Mains Filter and Indicator Circuit
From the mains plug ( fitted with a 3A fuse ), the mains passes into the set via connector GN0304 and
into the fuse, F701 ( 3.15A anti-surge ). After the mains switch, S701, the mains applied indication neon
is connected across the live and neutral lines via R701 and R702. From this point the mains is fed to
the de-gauss circuit, via L701 and the positor POR701, undesirable spikes generated by the de-gause
operation, are removed by C702. Choke L701 provides further noise suppression. After L701 the mains
is also sent to the standby control circuit. Finally, after passing through L702 and L703, the mains is
supplied to the bridge rectifier.