The Audio circuits are muted briefly when power
is first turned On to prevent a "thump" heard in
the speakers caused by Power Supply voltage
build-up. The control of Power On Muting is
provided by FETs Q204 and Q203 and is applied
to the inputs of Power IC301 and IC302. The two
FETs are normally On and require a positive
voltage at their gates to turn Off. When the
Power Relay latches, 120Vac is switched to the
Stereo Amp power supply. The bridge power
supply develops 45Vdc for Audio Power Outputs
IC301 and IC302. A full wave power supply de-
velops 15Vdc, which is regulated to 8Vdc by
zener Z401. IC201 is powered by the 8Vdc
supply. Also Q201 and Q202 Mute Drivers use
the 8Vdc to control the Muting FETs Q203/Q204.
As soon as the 8Vdc develops, Q202 saturates and
holds the FETs On. The muting action continues
while R224 and C225, a two second timing
circuit, charges toward 8Vdc. After about two
seconds, Q201 base is forward biased. Q201
turns On, and pulls Q202 base to ground. Q202
turns Off, and FET gates are pulled up by R222.
The FETs turn Off, which un-mutes the Audio
channels.
Figure 2 9 - Sound Processing Circuit
Figure 28- Sound Processor Logic
Encoder
Summary of Contents for 6810
Page 3: ...Figure 1 Signal Flow Block Diagram...
Page 15: ...Figure 14 TS10 Tuning System Block Diagram...
Page 20: ...Figure 20 Decoder Module Signal Flow Diagram...
Page 30: ...Figure 31 Comb Filter Module Figure 32 Comb Filter Circuit...
Page 35: ...Figure 37 CRT Drive Circuit 4...
Page 41: ...Figure 47 Keystone Trapezoid Generator o Figure 48 Side Pincushion Generator...
