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Some of the component placements are somewhat confusing. Refer to the above for resistor placements.
R29 - 1K
R30 R32 R37 - 1.5K (note: R30 & R37 are next to each other)
R33 -1.8K
R31 R34 R36 - 2K
R35 - 2.2K
R38 R39 R40 R41 R42 R43 - 3.3K
C39 C45 C46 - 0.1 uf
C42 C43 C44 - 0.15 uf
C38 C40 C41 - 0.22 uf
C47 C48 C49 – 22 uf -
Caution! Make sure the part is installed with the proper polarity as shown above.
Main Audio Filter Tests
Apply 9v.
Check the input 3.3v to the board to make sure it is ok.
Check the 5-8v input to the board to make sure it is ~7v.
Check all four corner pins of U5 - TLV2464. They should all be at ~ 1.5v
Connect the headphones and turn up the volume. The static hiss out of the receiver should be quite loud.
The level pf this hiss will significantly reduced when the receiver is tuned up later. You should be able
to vary the SCAF filter pot and hear the audio bandwidth of the hiss change.
In addition, the audio may have a feedback "howl" at the highest audio gain setting. This will also go
away as the receiver is tuned up in later sections. If the howl is at almost all gain settings, the 3.3v input
is probably way low (like 2v) and the voltage regulators are no longer providing the inter-stage isolation
that happens when they regulate. A low voltage is due to high current drain and usually means an IC
was installed backwards.
Disconnect the 9v battery.
Norcal NC2030 v5
12-18-05
Page 78 of 128
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