ENDEVCO
www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826]
IM 2680/5 083119
10
The gain adjustment is a 12-turn (typical) 500 000-ohm (±0.1%)
potentiometer with mechanical stops at the extreme clockwise (cw) and
counterclockwise (ccw) positions. Maximum resistance (minimum amplifier
gain) is obtained in the extreme cw position. Signals are present at both
ends of the potentiometer, but signal changes may not occur during the
final two turns. A 1/16” (1.6 mm) flat blade screwdriver is recommended
for adjusting the potentiometer.
Airborne amplifiers shipped as a component of an Endevco system
consisting of an airborne amplifier with a cable assembly and either an
accelerometer or microphone; normally have the gain factory-set to a
specific level, and the gain-access screw solder-sealed to the case of the
airborne amplifier. The gain-access screw must be sealed to the case
with solder (recommended), glyptol or epoxy for it to meet humidity
specifications during operation.
Units shipped as single items of equipment have the gain potentiometer
set to the maximum rated gain and the gain-access screw temporarily
seated in the threaded access hole. Users may adjust the gain to a desired
gain setting prior to installation of an airborne amplifier. See table 1 to
determine the applicable gain range.
4.5.1
Unsoldering the access screw
Should it become necessary to remove the screw from a unit that has been
solder sealed, follow the instructions as follows:
•
Preheat an oven to 212°F (100°C).
•
Place airborne amplifier in the preheated oven for a period of time
sufficient for the airborne amplifier to stabilize.
•
Insert the 5/64”Allen wrench into the access screw (per figure 4) and
place a soldering iron adjacent to the access screw as shown in figure
4
•
Apply ccw torque to the Allen wrench and remove the access screw
when solder seal is molten.
CAUTION
When removing the access screw, care should be exercised to prevent
molten solder from entering the airborne amplifier.
4.5.2
Sealing the access screw
A new access screw should be used to seal the gain adjust hole. Installing
used access hole screws could prevent the airborne amplifier from meeting
the humidity specifications. Follow the steps below for installing and
sealing the new screw:
•
Install a new access screw into the gain adjust hole.
•
Preheat oven to 212°F (100°C).
