Product Manual

SERVICE MANUAL 711380 REV. D
WELCH ALLYN UNIVERSAL DESK CHARGER 1
1.1 About the 711
Universal Charger
1. It is intended to operate from an AC power source
from 100V to 275V. Along with a standard IEC
connector, this will be an international unit. Per-
formance tests show that the charger will operate
down to 90V with a single handle receiving a full
charge rate (65 mA), and two handles receiving
>45 mA. This exceeds our present 71110 handle
which provides 20 – 30 mA under the same condi-
tions.
2. It is intentionally designed to charge handle /
battery combinations that range from 2.5V to 5.5V
end-of-charge voltages. Given the present high /
low line and high / low battery voltage combina-
tions, the 71110 charger varies its charge current
from 20 mA to 80 mA. The universal desk charger
is designed to vary by less than 10% under these
conditions (typically less than 2%).
3. The universal desk charger provides charge
indicator LED’s as well as power on indicator
LED(s).
The universal desk charger electrical circuitry is designed
to provide a safe (if not optimal) trickle charge profile for
all Welch Allyn handles. It is intended to replace the
71110 Desk Charger. However, the major improvements
over the 71110 that directly affect the electrical design
are:
1.2 Block Diagram
AMBER LED
(on when current is active)
Current
Limit
AMBER LED
(on when current is active)
Current
Limit
P
O
W
E
R
I
N
P
U
T
POWER
ON
LED
Voltage
Limit
Voltage
Limit
Output
Output
Charging Well #1
Charging Well #2
IMPORTANT: for a complete
description on the function and
use of the 711 Universal Charger,
as well as user safety warnings,
cautions, and warranty informa-
tion, read and understand the 711
Universal Charger Operator’s
Manual part number 711371
(English). Other languages are
available.