A M S - 1 0 2 7 A M P L I F I E D S P E A K E R S T A T I O N
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MAINTENANCE
GENERAL MECHANICAL OBSERVATIONS
Elimination of cabinet and component sympathetic vibrations (resonances)
requires considerable attention to mechanical details. Because of this, and the
physical constraints of the speaker’s acoustic enclosures, even minor changes to
any of the mechanical details of the unit can seriously impair its acoustic
performance. This especially applies to the speaker baffles. If mechanical work on
the unit is necessary, be sure to make adequate notes to permit accurate
reassembly.
Due to our unique method of shielding, the magnetic shielding is usually
degraded slightly by any disassembly of the unit, except removal of the rear panel.
Almost any maintenance or repair will require removal of the cover. If an
immediately adjacent video monitor shows magnetic interference after
reassembly of the unit, it must be returned to the factory to restore the shielding
completely.
Refer to the overall unit interconnect block diagram which appears later in this
chapter for assistance in tracing the signal path through the detailed schematic.
GENERAL AUDIO CIRCUITRY OBSERVATIONS
Since a single-sided power supply is used, all amplifier sections are “biased” with
a 1/2-supply reference, so all opamp signal terminals on the main board should
have a DC level of 12 ± 0.7V.
Signal inputs to the main audio board are via the balanced XLR analog inputs or
unbalanced RCA inputs.
Signal feed points for level meters and the phase indicator are immediately after
the input stage, and before the volume control section.
The signal pick-off for the headphones is after the volume and balance controls.
Analog switches mute the speakers, controlled by circuitry, which senses
connection of headphones to the jack.
The power amps are attached to an aluminum heatsink plate (which is also
connected to the circuit common for these devices). The heatsink plate forms an
operational module separate from the chassis, which allows access to the solder
side of the circuit board while power is applied to the circuitry. To avoid thermal
shutdown of the power amp(s), they should
not
be operated without their tabs
being fastened to the heatsink plate.
Variations in the frequency response of different production runs of drivers has
sometimes required minor adjustments in the equalization/crossover components
in individual runs of units. Some of these components may have values slightly
different than those indicated in the schematic, which are the nominal ones. If
If you disassemble the
AMS-1027 unit, you may
impair the unit’s magnetic
shielding.
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