ZETRON 4000 Series, Installation Manual

Page: 187 / 418

187
Auxiliary Audio Input Adjustment
Auxiliary Audio Input Adjustment
Auxiliary audio input is not run through an AGC circuit, but it is notch-filtered when
transmitted over tone-controlled channels. The adjustment is best performed while
monitoring the deviation on the channel over which the auxiliary audio is being
transmitted. Fully compressed voice from the console will be at 0.75 Vrms (0 dBm, 2.2
Vpp).
Model 4018 input audio adjustment potentiometer is R63, labeled AUX. See Figure 35 for
its location. Models 4118 and 4217B adjustment is labeled AUX IN and is located on the
back of the console (see Figure 37 ).
Other Audio Adjustments
Speaker Minimum Audio Level
The minimum audio level is the level of audio produced when the front panel volume
knobs are turned completely down.
To set the minimum audio level, adjust the potentiometers next to the associated speakers
on the display board. The Model 4018 select speaker adjustment is R32 and unselect is R1.
Models 4116B, 4118, and 4217B select speaker is R32 and unselect is R5. These are set at
the factory for no audio output (completely counterclockwise) with the volume knobs
completely off.
Other adjustments on the display board are set at the factory and should not require
adjustment. If the display board is replaced or repaired, make the adjustments listed in
Table 81 .
Table 81: Replaced Display Board Adjustments
Model 4018 Model 4118
and 4217
Description
R21 R1 Display contrast, adjusted for best viewing
R34 R20 Select speaker DC bias, adjusted for
minimum DC voltage across select speaker 0
±30 mV
R7 R4 Unselect speaker DC bias, adjusted for
minimum DC voltage across unselect speaker
0 ±30 mV