J. W. Davis & Company D-250AL User Manual - page 4
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...
IV. THE FRONT PANEL
V. THE BACK PANEL
-4-
1. Volume Control: Adjusts the amplifier’s output level.
2. Circuit Breaker: If the amplifier is continuously over-
loaded, this AC line circuit breaker will trip. Another cause
for the circuit breaker to trip is that the internal temperature
surpasses the safe operating range. Pushing the plunger will
reset the breaker. However, it is important to first correct the
problem causing the overload or overheating. (Additional
protection is provided by fuses in the power supply.)
3 & 4. Power Switch and Indicator (ON - OFF): Controls
power to the unit. The green LED will light when power is
being received.
5. Peak Power Overload Indicator: 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.
Relay. A relay has been added to the D-250AL circuitry to
prevent any DC from reaching the output. A slight delay of the
audio will be noticed when the unit is turned on as well as an
abrupt disconnect of the audio when the unit is turned off.
Overload protection. If a short circuit or overload occurs in
the amplifier, or if the speaker line is overloaded or shorted,
the AC line circuit breaker on the front panel will open.
Correct the problem, then push the button to reset. If the
circuit breaker will not reset, have the unit serviced by a
qualified technician.
1. AC Line Cord: Three conductor line cord for AC voltage
.
2. AC Convenience Outlet: Grounded outlet to run
additional equipment (2 amp maximum).
3. Input Terminal Screw Strip: This strip is designed to accept
either a 600
Ω balanced input or a tel-page balanced input. These
inputs, differing only in sensitivity, are
designed for wide acceptance without the
need for any accessories.
Tel
G
600
Ω
4. Gain Control for 600
Ω
Ω
Ω
Ω
Ω Tel-Page Input: This control adjusts
the level of the 600
Ω tel-page input without affecting the level of
the high impedance input. It works in conjunction with the volume
control located on the front panel. Both controls effect the 600
Ω
tel-page input, and will automatically mute the Hi-Z (music)
inputs. To defeat VOX mute, see Section VIII, page 6.
5. Input/Patch: Two high impedance inputs connected in
parallel for signal input and for strapping to a second ampli-
fier that will increase the wattage of the entire system.
6. Output Terminal Strip: 8 OHM - Bridged output for
an 8
Ω direct voice coil speaker. Do not ground either
terminal. 25V/70.7V - For constant voltage speaker lines
using speakers with line matching transformers. Connect
the speaker line to “common” and either 25V or 70.7V
output.
7. 25V/70.7V Line Output Switch: Dual purpose switch
connecting the output transformer in and out of circuit. It
also controls a low-cut filter designed to prevent low
frequency in and out of circuit. It is designed to prevent low
frequency overload of speaker line transformers and horn
type speakers. For either 25V or 70.7V operation, the
switch must be set to the LINE IN position.
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