Specifications

CA10 Course Notes
Sharp Electronics (UK) Limited
CE Technical Support GroupPage 24
Supplies generated by the line stage
A number of conventional supplies are generated from the line output transformer, EHT, Focus, G2, A1
and CRT heaters. A further +/- 15V is also generated for the vertical output stage. Also there is a +2V
supply for the east/west diode modulator and a -10V supply which along with the +2V supply is used to
drive the line output transistor. See the Line drive circuit description section of these notes for more
details on this.
Supply Name Voltage ( approx ) Purpose Point of Generation
EHT 28kV CRT final anode Top of split diode chain
Focus 8kV CRT focus grid Split diode chain
G2 500V CRT grid Split diode chain
CRT Heaters 3VAC CRT Heaters Pin 1 of T601
+45V +45V East/west correction circuit supply D510, Pin 6 of T601
+45V +2.0V Line drive D605, Pin 10 of T601
+15V +15V Vertical output supply D609, Pin 9 of T601
-15V -15V Vertical output supply D608, Pin 5 of T601
-45V -10V Line drive D602, Pin 6 of T601
As the +/-15V supplies are generated by the line stage, there will be no vertical scanning or sound output
until these have come up ( note that the sound output stage is supplied from the chopper +/-18V supplies,
but no current will be supplied until it starts to amplify the output from IC305, this is muted until the line
stage is fully functional ). Also the +45V supply will not be established until the line stage is running. This
effectively ensures that the line stage ‘soft starts’ and therefore significantly reduces the risk of component
failure as the receiver is turned on, i.e. current is taken from the chopper supply in the following time
sequence :-
1. Line stage starts up at 31.25kHz using the -18V and +13V supplies from the chopper.
2. Feed back is received from the line stage and IC201 switches to 15.625kHz.
3. Line stage runs ( +150V from the chopper and -10V/2.0V from line stage ).
4. Vertical stage starts up using the +/-15V supplies from the line stage.
5. Current is drawn for the sound output stages as the output from IC305 is turned on.
6. RGB drive is turned on and current is drawn from the +150V supply from the chopper
by the CRT drive IC.
Note that the CRT drive amplifier is not supplied from the line output stage, as in other Sharp television
chassis, but is derived direct from the 150V supply generated by the chopper stage.