This PCB selects between one of five s-video & composite video inputs for the
main input & zone 2 video. It also controls the volume control for Zone 2 & 3.
The main input video is selected using IC200 (LA73031V video mux) under
the control of IC205 & IC208 (74HC595 serial to parallel converters, controlled
by SPI Clk, Data & Vid IO Mux Latch). Inputs are selected using INSEL1,
INSEL2, INSEL3 (Z2 INSEL1, Z2INSEL2, Z2INSEL3 for Zone 2 via IC203 –
LA73031V video mux).
As there is only one sync separator within each LA73031V, it is necessary to
select if this is used for S-video or composite (this means that once composite
video is selected as the source, it is not possible to autodetect S-video) -
SYNC CTL selects, low = Svideo, high = composite.
There are two buffered (IC201 & IC202 – BA7623F video buffers) tape
outputs, VCR & PVR which can be muted with VCR Mute & PVR Mute
respectively through a transistor network. Each output is muted when that
input is selected to prevent feedback, otherwise the output is a copy of the
composite or S-video signal going to the main zone.
Zone 2 video is buffered through IC204 (BA7623F video buffer) and can also
be mute, if required using the signal Z2Vid Mute & a transistor network.
When S-video or composite inputs are not used, V MUX STBY should be
asserted high. Note: this will disable both the main Zone & Zone 2 S-video &
composite muxes.
Video Input Truth table:
(Z2)INSEL1 (Z2)INSEL2 (Z2)INSEL3 (Z2)SYNCCTL
0 0 0 1 AV
comp
0 0 1 1 SAT
comp
0 1 0 1 DVD
comp
0 1 1 1 PVR
comp
1 0 0 1 VCR
comp
0 0 0 0 AV
S-vid
0 0 1 0 SAT
S-vid
0 1 0 0 DVD
S-vid
0 1 1 0 PVR
S-vid
1 0 0 0 VCR
S-vid
Volume control for Zone 2 & 3 uses IC300 & IC301 (BD3812F volume
controls) via a two-wire interface (Zone SPI Clk & Zone SPI Data). IC300 has
address D2, D1=1, IC301 has address D2, D1=0. The volume controls can
be muted from IC208 (Serial to parallel converter) using Z2 vol mute or Z3 vol
mute. The outputs are also relay controlled for powerup/down with Z2 Mute &
Z3 Mute directly from the PW338 using RLY300 & RLY301 as shunt relays.
The +7VA & -7VA required for the BD3812F volume controls is derived using
REG300 (LM1117) & REG301 (LM337LZ) from the +15V & -15V from L123.
L114AY – Video input – output