KEPCO EL Series Electronic Load Operator Manual P/N 243-1295 Firmware Version 3.63 through 3.86 - Manual (Page 24)

2-6
SERIES EL 070312
2.3.1 CHANGING MAINS POWER VOLTAGE
The load can be operated from either 120V a-c, ±10%, 50/60 Hz or 240V a-c, ±10% 50/60 Hz.
To change from one mains operating voltage to the other requires repositioning of line voltage
selection jumpers located on the Master Control Board and must be done only by authorized
personnel. NOTE: Carefully tag and retain all attaching hardware for use during reassembly.
NOTE: Conversion of Dual Channel Models (D suffix) from 120V a-c to 240V a-c is not autho-
rized; please contact factory for assistance.
1. Disconnect all line voltage sources and UUT sources.
2. Open the load cabinet by removing the top cover as described below:
a. Loosen and remove five screws holding the top cover to the load on each side.
b. Loosen and remove four nuts holding the top cover to the load rear panel. The top
cover is held in place by four threaded studs.
c. Loosen and remove four screws holding the top cover to the load front panel. For ease
of removal, use a non-metallic support tool through the front panel vertical ventilation
slots to support the top cover as the screws are removed. With the screws removed,
the tool can be used to elevate the top cover above the front panel so it can be grasped
and removed from the load.
3. Refer to Figure 2-5 and remove the Master Control Board as follows:
a. Unplug 10-pin ribbon cable at top of Master Control Board.
b. Unplug 16-pin ribbon cable from Front Panel Display Board at top of chassis.
c. Unplug front and rear fan connectors from Master Control Board.
d. From outside of side panel, remove four Allen Head screws holding the Master Control
Board mounting plate to the load side panel.
e. To allow the transformer on the Master Control Board clearance it is necessary to
remove one Power FET Module (PFM) board (see Figure 2-5). Disconnect two PFM
board interconnection cables, then remove four groups of four screws (each with one
flat washer and one lockwasher) and two sets of brass nuts (each with one flat washer
and one lockwasher).
f. Raise Master Control Board assembly until the two small black mains voltage selection
jumpers are visible (see Figure 2-6). NOTE: It may be necessary to remove nut secur-
ing wire strap holding front fan connector wires to fully remove board.
4. Using long-nosed pliers, remove the jumpers and relocate them to the desired position (see
Figure 2-6). NOTE: Two jumpers used for 120V a-c operation, only one jumper used for
240V a-c operation.
5. Reassemble the load by reversing the above steps. CAUTION: When reinstalling the
PFM Board, it is important to torque all screws and nuts to 1.5Nm (13.8 in-lb).
6. Change the mains fuse to correspond to the type and rating suitable for the selected mains
voltage operation (see Figure 2-3).