Model 2870A Manual p/n 752-638, Rev 20120906 Page 2 of 4
General Description and Application
The Model 2870A GPU is a modular switching-mode power supply designed to provide pilots and
aviation maintenance professionals with a portable, affordable source of stable, high-current, noise-free
DC power that replicates the in-flight electrical environment. Its rated output is 28 Volts DC, up to 70
amps continuous, from a 20A 120 VAC 60 Hz input. It will safely provide continuous power for the most
delicate electronics with stable, ripple-free DC up to its full rated output. It is ideal for:
•private aircraft hangars
•baggage-carried backup power source for remote sites
•FBOs, avionics & maintenance shops
•air shows and aircraft exhibitions
•aircraft production and testing facilities
Operation of sophisticated avionics and electrical equipment by poorly regulated, noisy power sources
risks costly damage. This portable GPU is designed as a practical alternative to large, expensive start
carts, battery chargers, and other transformer/rectifier-based power systems designed to turn electric
starter motors. It is suitable for ground operation of airframe systems such as:
•avionics for familiarization & training, database updates, testing or maintenance
•aircraft heating, air conditioning and ventilation systems
•cabin entertainment systems
•hydraulic and electric motors for actuating landing gear systems
•electrical equipment, motors, and lighting
•electronic equipment and gyros
Operating Conditions & Limitations
The 2870A GPU is fan-cooled and relies on unobstructed access for cooling air to enter the rear vents and
exit the bottom of the cabinet at the front. The GPU should operate on a clean, hard surface so that debris
cannot be ingested. Its design assumes a dry operating environment. If used outdoors, it is the operator’s
responsibility to insure that the unit is not exposed to moisture.
At full output, the GPU can draw up to 19 amperes and therefore should be connected to a dedicated 120
volt AC, 20-amp wall receptacle. Connecting the GPU to a standard 15-amp wall outlet will limit its
output to about 55A, but otherwise it will function properly. If an extension cord is to be used with the
GPU, a 3-pin grounded 12-gauge HD type of less than 50 feet is recommended – the shorter, the better.
Connecting GPU to Aircraft
Consult your Aircraft Flight Manual, Pilot’s Operating Handbook, or Aircraft Maintenance Manual for
the correct procedures for connecting an external power source to your particular aircraft. Our general
recommendation is to turn the GPU ON and observe its output voltage stabilized at approximately 28
volts before connecting its output cable to the aircraft’s external power receptacle. Similarly, we
recommend removing the GPU’s output cable from the aircraft prior to turning its power switch OFF.
This procedure will avoid any possibility of subjecting the aircraft electrical system to turn-on or power-
down transients. If the GPU voltage is less than 24 volts, do not connect to aircraft, of if connected,
discontinue operation and seek repair.
The GPU rear panel has a 20A circuit breaker. If the GPU shuts down while operating, turn its power
switch to the OFF position, disconnect it from the aircraft and check for any potential overload or short
circuit conditions. Once resolved, reset the circuit breaker, turn power switch to the GPU position to
restore GPU output, then reconnect to the aircraft.
