Chapter 4: 25
4.4.2.2 Probeboard schematic (061-0177-0x)
Page 3: The Left Reference Microphone signal arrives at J7 pin 1. U6 and associ-
ated components re-reference the microphone ground from chassis to the
local Analog Ground. The Left Probe Microphone signal arrives at J7 pin
3. U10 and associated components re-reference the microphone ground
from chassis to the local Analog Ground. The Right Probe microphone
set does the same using J8, U16, and U17.
Page 4: All four microphone signals arrive at U7-A and U7-B. This part connects
one of the microphone signals to ChanA, and another one to ChanB.
U8-A, U12-A, and associated components are the ChanA 24dB prescaler.
U12-B, U8-B, U12-C, and U11-A, and associated components are the
ChanA probe equalizer. U11-A also acts as the positive half of the ChanA
differential line driver which drives the MICA+ line. U11-B, U18-A, and
associated components are the negative half of the ChanA differential
line driver which drive the MICA- line. Turning the negative driver on in-
creases the output of the differential receivers on the connectorboard by
6dB. So the negative half of the differential driver is also the 6dB Pres-
caler. Channel B has the same circuits shown below those just described
on the schematic. U28 is a serial to parallel output shift register that the
microcontroller U1 uses to control the multiplexer, the prescalers, and
the equalizers on this page. The signals on U28 called SPIMOSI, SPICLK,
SPICSL come from the SPI interface on the microcontroller U1 on page 1.
Page 1: The MICA+ signal is sent out J2 pin 1. The MICA- signal is sent out J2
pin 8. The MICB+ signal is sent out J2 pin 2. The MICB- signal is sent
out J2 pin 9. These signals are then sent to the Connectorboard.
4.4.2.3 Connectorboard schematic (061-x172-0x)
Page 3: The two phases of the two microphone signals arrive on both J3 and J4
pins 1, 8, 2 and 9.
Page 2: The MIC1A+ and MIC1A- signals are RF filtered and then converted
from differential to single ended with an AREF ground reference by
U7-A, U7-B and U8-A and associated components. The AREF ground is
sampled from the Daughterboard analog ground. The other 3 microphone
differential signals are handled in the same way by those circuits below
and to the right of those just described on the schematic. They are then
renamed MIC_1A, MIC_1B, MIC_2A and MIC_2B.
Page 3: MIC_1A, MIC_1B, MIC_2A and MIC_2B are sent to the Daughterboard
via J5 pins 1, 2, 3 and 4.
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