Precision Electronics AXIOM 250 User manual

Grommes~Precision
Precision Electronics
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.
Grommes~Precision
Grommes~Precision
847-599-1799 · 800-SINCE-46 · FA : 847-599-6178
1331 Estes Ave. · Gurnee, IL 60031 · USA
www.grommesprecision.com
AXIOM 250
INSTRUCTION MANUAL
Unpacking Procedures   2 The Back Panel   5
Installation Information   2 Speaker Installation   6
Description & Specifications   3 The Auto-Mute Circuit   7
Product Overview   4 Using Trumpet Speakers   7
The Front Panel   4 Maintenance   7
Troubleshooting 8

I UNPACKING PROCEDURES
INSPECTION
This unit was carefully checked and packed before leaving the factory. However, it is always a good
idea to inspect the shipping container and unit for indication of improper handling. If the unit has
been damaged, make an immediate claim to the dealer or distributor from whom it was purchased. If
the unit was shipped to you, notify the transportation company without delay, saving all packing ma-
terials, in order to process the claim.
INITIAL PERFORMANCE CHECK
Continue the inspection by running a performance check. Connect a test speaker to the 8 ohm direct
output terminals see page 6) and a tuner, tape deck, or CD player to the auxiliary input and set the
controls for operation. CAUTION: TO PROTECT THE SPEAKER FROM DAMAGE, DO NOT TURN
THE UNIT ON UNTIL ALL CONNECTIONS HAVE BEEN MADE. IN ADDITION, MAKE SURE THE
UNIT IS GROUNDED BEFORE TESTING. If the unit should be inoperable and no damage is noted,
please notify the factory at 1-847-678-3222 and ask for Technical Support.
II INSTALLATION INFORMATION
RACK MOUNTING
For best results use a 10-32 class UNF-2B or 12-24 class UNC-2B rack and 0.625 inch machine
screws metric: M5X8-6H or M6X1-6H, 15.88mm). It is recommended that the drive of these screws
be phillips in order to protect the finish from unnecessary scratches. Also recommended are nylon or
plastic washers which will not only help protect the finish but also aid in retaining the screws.
CONVECTION, FAN COOLING, AND VENTILATION
This unit is cooled via convection and therefore designed for continuous operation. Do not block the
unit’s heatsink fins or vent holes located in the cover. If the unit will be rack mounted, you must util-
ize a cooling fan that is capable of exhausting not less than 300CFM. The fan must be mounted to
the inside top of the rack, above the amplifier.
TECHNICAL SUPPORT
A troubleshooting chart is located at the end of this manual for your convenience. If you are in need
of further assistance, you can reach our design engineers at 1-847-599-1799. Grommes~Precision
is based in Gurnee, Illinois and is on Central Standard Time. Our hours of operation are Monday -
Friday from 8:00am to 4:00pm. Troubleshooting information can also be found at our website www.
grommesprecision.com.
AXIOM 250 INSTRUCTIONS
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Thank you for purchasing from Grommes~Precision!
Grommes~Precision and its commercial audio division, Precision Electronics, has been designing,
engineering, and manufacturing quality sound equipment in the United tates since it started opera-
tion in March of 1946. Over a half a century of quality, service, and flexibility as “Your Personal
Manufacturer” have made us one of the last American audio manufacturers. If you have any ques-
tions with this or any one of our other fine products, give us a call. When you talk with a member of
the Grommes~Precision team you’ll be speaking with someone who had a hand in concept, design,
production, or testing of this very product.
Grommes~Precision
Precision Electronics
847-599-1799 · 800- INCE-46 · FAX: [phone]
1331 Estes Ave. · Gurnee, IL 60031 · U A
www.grommesprecision.com
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.

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AXIOM 250 INSTRUCTIONS
III DESCRIPTION & SPECIFICATIONS
• 250 Watts of Continuous RMS Power
• Independent Input Gain Control for 600 ohm/Tel-Page
• Automatic voice activated Hi-Z muting.
• Built-in Transformer isolated outputs for 25V and 70.7 volt line operation.
• Built Tough: Multiple Protections Including Relay, Short Circuit, & A/C Circuit Breaker
• No maintenance: Convection Cooling
• Rugged Power Supply Designed for Constant & Consistent Duty.
FEATURES
Power output: 250 Watts RMS
Mixing Channels:
1.5 Main Channel + Independent 600 ohm/Tel-Page Input)
Inputs:
2 Aux in Parallel; 600 ohm/Tel-Page
Input Sensitivity/Impedance:
50mV/600 ohm Tel-Page); 0.50V/600 ohm 600 ohm), 0.50V/10K
ohm High Impedance)
Outputs:
8 ohm, 25V, 70.7V
Distortion at Rated Output:
<0.3%THD
Frequency Response: +1dB 20 to 20kHz Direct Output); +1dB 50 to 15kHz 25V or
70.7V)
Hum/Noise: 90dB Below Rated Output
SPECIFICATIONS
• Optional Isolation Transformer Available • Tel-Page Line Lightning Suppressor TLS)
• Speaker Line-Lightning Suppressor SLS)
ACCESSORIES
DESCRIPTION
The AXIOM 250 is a 1.5 channel high fidelity commercial audio amplifier that provides 250 watts of
continuous RMS power directly into 8 ohm or transformer isolated 25V or 70.7V lines. Designed for
all-in-one telephone paging solutions, the AXIOM 250 includes a balanced 600 ohm/Tel-Page input
with a tamper resistant volume control located on the rear panel) that is capable of muting two aux
inputs defeatable), which are strapped in parallel
.
WARNINGS
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS UNIT TO RAIN OR MOISTURE
WARNING: DO NOT USE THIS IN LIFE-SAFETY APPLICATIONS THIS UNIT IS FOR COMMERCIAL AUDIO ONLY
CAUTION: In the event the transformer’s thermal breaker does not reset, have trouble investigated by an authorized service techni-
cian or return it to the factory
CAUTION: There are no user-replaceable parts within the unit Have all internal servicing done by a qualified technician
CAUTION: These devices are not intended for use in hazardous locations as defined by the National Electrical Code (NEC) and by the
National Fire Protection Association (NFPA)
Grommes~Precision
Precision Electronics
847-599-1799 · 800- INCE-46 · FAX: [phone]
1331 Estes Ave. · Gurnee, IL 60031 · U A
www.grommesprecision.com
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.

4 of 8
AXIOM 250 INSTRUCTIONS
V THE FRONT PANEL
1 - VOLUME CONTROL
This gain control adjusts the master volume
level of output for the amplifier.
2 - CIRCUIT BREAKER
Pushing this plunger will reset the circuit
breaker should the breaker trip. There are two
reasons why the circuit may need to be reset: 1)
the amplifier is continuously being overloaded; or
2) the internal temperature surpasses the safe
operating range. NOTE: Before resetting the cir-
cuit, be sure to first correct the problem causing
the overload or overheating.
3 - POWER SWITCH
This switch turns the unit on or off.
4 - POWER INDICATOR
This green LED will light when the power is
switched on.
5 - OVERLOAD INDICATOR
This red LED will light/flash at full power and
on peaks. A steady bright glow could indicate a
shorted speaker line, too much load, or oscillation
in the system.
IV PRODUCT OVERVIEW
Grommes~Precision
Precision Electronics
847-599-1799 · 800- INCE-46 · FAX: [phone]
1331 Estes Ave. · Gurnee, IL 60031 · U A
www.grommesprecision.com
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.

5 of 8
AXIOM 250 INSTRUCTIONS
VI THE BACK PANEL
1 - AC Line Cord
Three conductor line cord for AC supply volt-
age.
2 - Grounded AC Convenience Outlet
Grounded outlet to run additional equipment
2 amp maximum).
3 - Input/Patch
These are two high impedance inputs con-
nected in parallel. One is for signal input, the
other for strapping to a second amplifier that will
increase the wattage of the entire system.
4 - 600 ohm/Tel-Page Input Gain Control
This recessed control adjusts the level of the
600 ohm Tel-Page input without effecting the
level of the high impedance input. It is factory
preset at 0. This input will automatically mute the
Hi-Z inputs. To defeat this feature see “Part VIII.
The Auto-Mute Circuit” on page 6.
NOTE: This control works in conjunction with the
master volume located on the front pane. If the
master volume control is set at 0, then, regard-
less of how loud the 600 ohm/Tel-Page gain is
set, the amp will not send an output to the speak-
ers.
5 - INPUT TERMINAL SCREW STRIP
This strip is designed to accept either a 600
ohm balanced input or a Tel-Page balanced in-
put. These inputs, differing only in sensitivity, are
designed for wide acceptance without the need
for any accessories. It is recommended to use
ground reference on the input whenever and
wherever possible.
6 - 25V/70 7V LINE OUTPUT SWITCH
If using 25V or 70.7V output, this switch must
be in the LINE IN position. This serves a dual
purpose: 1) it connects the output transformer in
and out of circuit, and 2) it controls a low cut filter.
This filter is designed to protect speaker line
transformers and speaker horns by preventing
low frequency overload.
7 - OUTPUT TERMINAL SCREW STRIP
Three 3) outputs are provided on this strip:
1) the voice coil output for a 4 ohm speaker load
and 2) the 25V and 70.7V speaker line output.
For more information on speaker load hook-up,
see “Part VII. Speaker Installation”
Grommes~Precision
Precision Electronics
847-599-1799 · 800- INCE-46 · FAX: [phone]
1331 Estes Ave. · Gurnee, IL 60031 · U A
www.grommesprecision.com
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.
MODEL: AXIOM 250
PRECISION ELECTRONICS, INC
A GROMMES~PRECISION COMPANY
1331 ESTES AVENUE
GURNEE, IL 60031
EIA #871
SERIAL #

VII SPEAKER INSTALLATION
CONNECTING FOR 25V/70 7V LINE OPERATION
For 25V output, connect the load to terminals 3 -) and 4 +). Do not connect any output wire to ter-
minal 6. For 70.7V output, connect the load to terminals 3 -) and 5 +). Do not connect any output
wire to terminal 6.
NOTE: When using the amp’s 25V or 70.7V line operation, the tap setting on the
proper impedance matching transformer determines the individual speaker’s power level. Using
these transformers allows the speakers to be placed at longer distances from the amplifier without
significant power loss. The number of speakers for a line-driven central amplifier system is limited to
the power available from the amplifier. The sum of all connected speakers’ power settings must not
exceed the total power available from the amplifier.
USING THE PROPER WIRE SIZE AND LENGTH
Cable distance should be kept as short as possible to minimize power loss. The chart below can be
used as a general guide showing various wire sizes and the maximum distance related to cable
loading that speakers can be placed from the unit for an approximate –0.5dB loss -12.5% power).
To allow for future expansion and distributed cable line loss, it is recommended the total system
wattage should not exceed 85% of the amplifier’s rated output. To determine the total system watt-
age, sum the wattage tap of all speaker s)/horn s) used.
AXIOM 250 INSTRUCTIONS
6 of 8
The AXIOM 400 is designed to be connected to 4 ohm speakers directly, or to variable impedance
speakers that match the amplifier’s line output voltage of 25V or
AWG
SIZE
LOW IMPEDANCE
SPEAKER LINE
4 OHMS 8 OHMS 16 OHMS 7.5W 15W 30W 60W 100W 125W 250W 400W 500W
10 120 240 480 - - 5,000 2,500 1,500 1,100 550 365 275
12 75 150 300 - 6,200 3,100 1,550 940 750 375 230 185
14 50 95 190 7,600 3,800 1,900 950 600 450 225 140 110
16 30 60 120 4,800 2,400 1,200 600 370 290 145 90 -
18 20 40 75 3,000 1,500 750 375 230 180 90 - -
20 15 25 50 1,920 960 480 240 150 110 - - -
22 10 15 30 1,200 600 300 150 95 - - - -
WIRE LENGTHS IN FEET
70 7V SPEAKER LINE
(FOR 25V LINE DIVIDE ALL 70 7V LENGTHS BY 8)
NOMINAL POWER IN LOAD
2 WIRE COPPER CABLE LENGTHS FOR SPEAKER LINES AT –0 5dB LOSS IN SPL (12 5% POWER LOSS IN WATTS)
CONNECTING FOR DIRECT 8 OHM OPERATION
Connect 8-ohm speaker s) to terminals 1 and 2. For proper signal
phasing, observe +/- polarity. NOTE: This output is a bridged. Do
not ground either of these two terminals.
FURTHER INFORMATION
For further guidance regarding speaker installation selection, placement, impedance matching with
or without transformers, phasing), see www.grommesprecision.com/precisionelectronics.
Grommes~Precision
Precision Electronics
847-599-6178 · 800- INCE-46 · FAX: [phone]
1331 Estes Ave. · Gurnee, IL 60031 · U A
www.grommesprecision.com
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.

VIII THE AUTO-MUTE CIRCUIT
DISABLING OR ENABLING THE AUTO-MUTE CIRCUIT
The AXIOM series of mixer amplifiers include a built-in automatic
mute circuit. The MIC/TEL-PAGE/600 ohm input channel, can auto-
matically mute the AUX channel. This unit is factory installed to auto-
mute, however, the mute is defeatable by moving the internal mute
jumper to its other position.
To defeat the auto-mute circuit follow these steps. 1) Unplug A/C and
all other connections from the unit. 2) Remove the hood and find the
input board located on the back panel. 3) On the board locate the
header X2 See the figure to the right). Change the shunt position
from positions 1 and 2 to 2 and 3 and the auto-mute will be defeated.
Connect shunt here to
disable the Auto-Mute
Connect shunt here to
enable the Auto-Mute
Factory-Preset)
The Auto-Mute Circuit
AXIOM 250 INSTRUCTIONS
7 of 8
Grommes~Precision
Precision Electronics
847-599-1799 · 800- INCE-46 · FAX: [phone]
1331 Estes Ave. · Gurnee, IL 60031 · U A
www.grommesprecision.com
Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.
XI MAINTENANCE
The AXIOM series is built to last and therefore comes equipped with multiple built-in protections in-
cluding relay, short circuit, and AC circuit breaker. If the unit is overloaded e.g. too many speakers,
shorted speaker line, mismatched line impedance [e.g. 8 ohm speaker on 70.7V line]) or overheated
e.g. obstructed or poor ventilation of the unit, mismatched line impedance) the unit will fail to provide
output. Overloading and overheating of the amp can lead to premature output failure.
RESETTING THE AC CIRCUIT BREAKER
If a the unit is overloaded or it overheats, the AC line circuit breaker on the front panel will open. Be-
fore resetting the circuit, determine and correct the problem causing the overload of overheating see
“Part X. Troubleshooting” on page 8 for a chart to help guide you in determining the cause of the
problem). If after exhausting the possibilities, the circuit breaker will not reset, have the unit serviced
by a qualified technician. NOTE: If the unit is rack mounted, you must utilize a cooling fan that is ca-
pable of exhausting not less than 300CFM.
REPLACING THE FUSES
Additional protection is provided by fuses in the power supply which protect the transformer. If an
output is shorted the fuses will blow. Before replacing the fuses, determine and correct the problem
causing the fuses to blow see “Part X. Troubleshooting” on page 8 for a chart to help guide you in
determining the cause of the problem). To safely replace the fuses: 1) Disconnect the AC power
cord; 2) Remove the top cover screws and cover; 3) Replace blown fuses with same type and size;
4) Reinstall the top cover securely; 5) Reconnect the AC power cord.
X USING TRUMPET SPEAKERS
LOW CUT FILTER AUTOMATICALLY ENABLED WHEN 25V/70 7V SWITCH SET TO “LINE IN”
If using 25V or 70.7V output, the 25V/70.7V line output switch on the back panel is set n the LINE
IN position. This serves a dual purpose: 1) it connects the output transformer in circuit, and 2) it con-
trols a low cut filter. This filter is designed to protect speaker line transformers and speaker horns by
preventing low frequency overload.

Grommes~Precision is an American manufacturer of original, custom, and private labeled audio/electronic equipment for use in commercial, consumer, and industrial applications since 1946.
Grommes~Precision
Grommes~Precision
847-599-1799 · 800-SINCE-46 · FA : 847-599-6178
1331 Estes Ave. · Gurnee, IL 60031 · USA
www.grommesprecision.com
8 of 8
X TROUBLESHOOTING
AXIOM 250 INSTRUCTIONS
SERVICING
If the unit requires service: 1) Obtain a Return Authorization RA) Number at 847-599-1799; 2) In-
clude a detailed written explanation outlining the nature of the problem and your contact information;
and 3) Ship pre-paid to Grommes~Precision, 1331 Estes Ave., Gurnee, IL 60031, USA. If the unit is
under warranty, repairs or a replacement will be made in accordance with Grommes~
Precision’s warranty policy.
SYMPTOM POSSIBLE CAUSE POSSIBLE SOLUTION(S)
Power Indicator on
Front Panel Does
Not Glow:
No AC power present. •Verify the unit is receiving AC power.
•Verify the AC outlet has proper AC voltage available.
Unit’s AC circuit breaker is
tripped.
•Verify the AC circuit breaker is not tripped. If so, depress
the plunger to reset.
•Verify the unit’s internal fuse s) has not tripped. If it has,
replace the tripped fuse with the same type and value fuse.
Overload Indicator
on Front Panel
Glows Steadily:
Input or output impedance not
matched
•Check that the proper input/output line impedance matches
the selected input/output connections used.
Signal in level too high •Lower the signal in level.
No Audio
Output:
No input signal source. •Verify that proper signal/level is being supplied.
Incorrect input signal connection •Verify that the signal input connection is correctly con-
nected.
Incorrect output connections •Check that the output connection has been properly made.
600 ohm/Tel-Page gain control
on back panel too low
•Check 600 ohm/Tel-Page gain control setting recessed on
back).
No Automatic
Muting of Input
Signal:
Internal jumper setting •Check that the internal mute jumper is not disabled. See
page 7).
Insufficient 600 ohm/Tel-Page
gain
•Check 600 ohm/Tel-Page gain control setting recessed on
back).
•Check 600 ohm/Tel-Page audio signal level is sufficient.
Low, High, or
Distorted Level:
Volume setting •Check the corresponding gain control on the front panel or
the 600 ohm/Tel-Page control recessed on the back).
Signal input level is too low •Check that adequate input signal level is strong enough.
Signal input level is too high •Reduce input signal accordingly.
Input or output impedance not
matched
•Check that the proper input/output line impedance matches
the selected input/output connections used.
Possible low resistance or
shorted wiring across the
audio in and/or across the
speaker out
•Check/correct system wiring.