J. W. Davis & Company D-250AL User Manual - page 6
NEW TECHNOLOGY
OLD RELIABILITY
J.W. Davis & Company
• 3030 Canton Street • P.O. Box 710219 • Dallas, Texas 75371-0219
Sales 800-527-5705 • Fax 800-388-9106 • Corp 214-651-7341 • Fax 214-939-0328 • sales@jwd.com • www.jwd.com
The Mark of the Professional...
VIII. THE AUTO-MUTE CIRCUIT
The JWD series of mixer amplifiers include a built-in automatic mute circuit. The MIC/tel-
page 600-ohm input channel can automatically 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 the A/C cord. 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.
DISABLING THE AUTO-MUTE CIRCUIT
If a the unit is overloaded or it overheats, the AC line circuit breaker on the front panel will open. Before
resetting the circuit, determine and correct the problem causing the overload of overheating (see
“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.
The D-250AL is built to last and therefore comes equipped with multiple built-in protections including 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
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 the same type and size; 4) Reinstall the top cover securely; 5) Reconnect
the AC power cord.
IX. MAINTENANCE
Connect shunt here to
disable the Auto-Mute
Connect shunt here to
enable the Auto-Mute
(Factory-Pres et)
The Auto-Mute Circuit
X. WARRANTY & TECHNICAL SUPPORT
For a period of five (5) years from the date of original purchase, J. W. Davis & Company warrants that it will
correct any defects in material or workmanship in the D-250ALwithout charge. However, this warranty does not
apply to equipment which in the opinion of J. W. Davis & Company has been subjected to abuse or accident,
improper installation or alteration in any way. If the D-250AL fails to operate during this period, return it prepaid to
J. W. Davis & Company Warranty Service with a letter explaining the problem and proof of purchase.
Should you require further technical support, please contact our Customer Service Department for assistance
through any of the channels shown below.
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NOTE: If the unit is rack mounted, you must utilize a cooling fan that is capable
of exhausting not less than 300CFM.