Service manual

STP 11-25R13-SM-TG
3 - 66
PERFORM AN AUDIO ALIGNMENT
113-575-8021
Conditions: In a tactical or garrison environment, given an audio console requiring alignment, source
inputs (microphones, CD players, and so on), audio amplifier, speakers, ATSG, multimeter with test
leads, extender cards (designed for the specific module), card pullers, specially made test cables,
alignment tool, electronic equipment tool kit, DA Form 2407, DA Pam 738-750, and manufacturers'
manuals.
Standards: The standards are met when the Microphone Input modules are aligned for 0 dBm and
Stereo Line Input modules and output amplifiers are aligned for 0 dBu.
Performance Measures Results
1. Review the DA Form 2407. P F
2. Turn ON and operations check the audio console to verify the deficient levels described
on the DA Form 2407.
P F
CAUTION: To prevent damage, turn OFF console power before removing or inserting
modules or accessories.
3. Align Microphone Input Select (MIS) module(s). P F
a. Turn OFF console main power. P F
b. Remove the module with a card puller. P F
c. Plug the module onto an extender card to allow access to trim pots without
interrupting power to the module.
P F
d. Reinsert module on the extender card into the console and turn ON power. P F
e. Adjust microphone gain level trim pots, MIC A and or MIC B, for 0 dBm with an
alignment tool. Observe levels on the selected VU meter, PGM or AUD.
P F
4. Align Stereo Line Input (SLI) module(s). P F
a. Turn OFF console power. P F
b. Remove the module with a card puller. P F
c. Plug the module onto an extender card and reinsert to the module slot. P F
d. Turn ON console power. P F
e. Connect a balanced +4 dB signal at 2 kHz into the desired input, A or B, from the
ATSG.
P F
f. Connect a dB-reading AC voltmeter to the A or B insert point and ground. P F
g. Adjust the appropriate gain adjustment trim pots for 0 dBu. Measure at both the
left and right insert points on channel A or channel B.
P F
5. Align Output modules. P F
a. Turn OFF power. P F
b. Remove and plug the module onto an extender card. P F
c. Reinsert module onto the extender card. P F
d. Turn ON power. P F
e. Feed a +4 dB stereo reference, 0.775 VRMS (equal to 0 dBu) at 2 kHz, into the
output module with the fader set at zero.
P F
f. Measure at the left and right Insert points for 0 dBu, the internal operating level,
and adjust the Input trim pots.
P F
g. If necessary, adjust the VU meters. P F
(1) Check the main outputs for +8 dBu. P F
(2) Adjust the left and right meter trim pots for 0 VU. P F
6. Document work accomplished on the DA Form 2407. P F