Panasonic EURO 4 Chassis Technical Manual page 131

3DQDVRQLF
Chapter 4
1.7. Secondary side
On the secondary side the transformer supplies the
following voltages :
1. B+ voltage used to supply the line output stage
2. 12V and 5V to supply an operating voltage to
the TV digital processing ICs.
3. 29V to supply the audio output stage
Although the secondary voltages are relatively stable
with short term load variations being compensated for
by IC801, it is still necessary to stabilise the following
voltages: 5V, 8V and 12V.
The voltages which do not require further stabilisation
are :
B+ voltages for the line output stage ,
29V supply for the A.F. output stage
+V
To Pin 1
IC801
1.7.1. Voltage Stabilisation
The stabilisation of the previously mentioned
secondary supplies is performed as follows:
:
A 15V supply which is fed from the
transformer T801 is fed to pin 1 of IC851
which is used to produce a stabilized 12V
supply. This 12V supply is also fed to IC853
pin 1 which produces a stabilised 8V supply
output via pin 2. and which is used to supply
the MSP IC2101.
The 5V supply is produced by feeding 7V to the
collector of series regulating transistor Q850 which at
its emitter, outputs a 5V supply. The zener diode D857
in the base of Q850 is used to maintain the base of
Q850 at a constant potential.
48
EURO 4D Supplement
To Pin 75
IC1101
+15V
To Q855
+B Protection