21
English --
INTERNAL MODIFICATIONS
WARNING!
Voltages in this equipment are hazardous to life. No
user-serviceable parts inside. Refer all servicing to
qualified service personnel.
This section describes AMS8100 modifications that can
be made using solder “jumpers” on the printed circuit board;
the pads where jumpers may be used are placed close togeth-
er so that a single solder drop functions as a jumper. Note too
that:
(1) The only printed circuit board legends used for these modi-
fications are jumpers (X’s) and resistors (R’s).
(2) Where resistors are to be added, through-holes are present
on the board.
(3)
For individual channel modifications, the first number of the
reference designation refers to its channel number, i.e.,
R1027 refers to a Channel 1 resistor, X7216 refers to a
Channel 7 jumper, etc. All references to Channels 1 through
8 in the following paragraphs use Channel 1 jumpers and re-
sistors as reference. Modifications affecting the Master sec-
tion are preceded by the number “9” (X901, etc.).
To gain access to the main printed circuit board, remove
the 8 Phillips head screws securing the top cover, and remove
the top cover. Most modifications can be made from the top of
the main board.
Direct Out to Mic--Level Output
The direct outputs for each channel are aux-level as they
come from the factory with aux--level outputs. These outputs
can be changed to unbalanced microphone--level outputs.
Procedure
: Locate X100 (near the 1/4-in. Direct Out jack).
Solder a 10 ohm resistor across it. Repeat these steps for all
channels needing modification.
Group Gating
With this modification, several channels can be grouped
together such that all of the channels activate whenever one of
the channels in the group activates. This is useful for miking a
choir, for example.
Procedure:
Locate pad X109. Solder a wire from this pad
to other channels in the desired group. For example, to gate
channels 1--4 as a group, solder a wire connecting X109,
X209, X309, and X409.
Disable Master Level Control
The Master gain control can be disabled so it cannot be
tampered with. The table indicates the resistor value to be
used for the desired gain.
Master Section Gain
Resistance
-6 dB
5.1 k
W
0
10 k
W
6 dB
20 k
W
Procedure:
Remove resistor R9230. Install new resistor
at jumper X914.
Limiter Threshold
All three threshold settings (+16, +8 and +4 dBu) can be
changed. To shift the threshold down by 6 dB (+10,+2, and --2
dBu), resistor R will be 82 k
W
. To shift the limiter thresholds up
by 6 dB (+22, +14, +10 dBu), R will be 330 k
W
.
Procedure:
Remove resistors R9177 and R9180. Install
new resistor R at jumper X907.
Local Aux Operation
In a linked system, the Aux input of any mixer appears at
each linked mixer’s output. With this modification, the Aux in-
put from a modified mixer does not appear at the outputs of
other linked mixers.
Procedure:
Remove resistor R9024.
Direct Out to Post-Fader
A channel’s Direct Out phone jacks can be changed from
pre- to post-fader.
Procedure:
Short jumper X106. Remove resistor R1011.
Repeat these steps for all channels needing modification.
Direct Out to Post-Fader Send/Return (Insert)
Changes a channel’s
1
/
4-
inch Direct Out jack to a post-
fader insert point. Send is tip of phone jack; return is ring. Insert
jacks are useful for inserting line-level signal processors into a
channel. For instance, a parametric EQ or compressor/limiter
can be inserted into a channel for additional processing.
Procedure:
Short jumpers X101, X102, X105 and X106.
Remove resistors R1011 and R1020. Repeat these steps for
all channels needing modification.
Direct Out to Gated Direct Out
This post-fader, post-EQ channel output is gated, but
without NOMA. In this mode, if the Local/Global switch is in
“Local”, a manual mix of channel inputs is present at the
mixer’s Output. The Off-Attenuation level of the Gated Direct
Out signal is infinite. For mic-level outputs, also perform the
“Direct Out to Mic-Level Output” modification.
Procedure:
Short jumpers X104 and X906 (in Master sec-
tion). Remove resistor R1011. Repeat these steps for all chan-
nels needing modification.
MUTE IN Precedence to OVERRIDE IN Precedence
With this modification and when both MUTE IN and
OVERRIDE IN logic are grounded for a channel, the Override
mode will take precedence. As supplied, the MUTE IN takes
precedence over OVERRIDE IN.
Procedure:
Short jumper X114. Remove resistor R1046.
Repeat these steps for all channels needing modification.
