Line Voltage Selection Power Block Wiring; Introduction - QRO Technologies HF-2500DX Instruction Manual

viewed from the front of the amplifier. Carefully place the plate transformer into the power supply
compartment cavity between the blower and the circuit board stack located behind the front panel
meters. Align the transformer with the chassis mounting holes and secure it to the chassis with
at least three 1/4-20 x 5/8 mounting screws and nuts. The fourth hole is rather difficult to access,
and it is not absolutely necessary to secure it. Locate the two amplifier's matching index
connectors. Connect the two matching connectors. There is only one way the two connectors can
go together. When the two connectors are locked together, you should hear a snap sound.
TUBES: The tube sockets are located on the left side of the amplifier. They each have seven
contacts which match the seven pins on the 4CX800A tetrodes. Remove the tubes form their
shipping cartons, and insert each tube into the socket making sure that the pins align with the
socket contacts. The tubes should seat without too much pressure applied. If you have to use a
lot of pressure, you most likely have the wrong pin alignment. If the tube pins and socket contacts
are not aligned, the amplifier will not function properly and damage to the tube may result. Once
the tubes have been properly seated in their sockets, slip the two anode connectors over the tube
anodes.

LINE VOLTAGE SELECTION POWER BLOCK WIRING

Your amplifier has been factory wired for 220 - 240 VAC 50/60 Hz. operation. If you need to
change the line voltage configuration, refer to the two Power Block Wiring Diagrams while reading
this section. Locate the Line Voltage Power Block. It is located inside the amplifier just behind the
filament & control transformer. It contains 5 screw connection terminals. It also has black and
white leads connected to it.
Convert 240 VAC to 200 VAC: One wire jumper (J1) is connected to terminals 3 & 4. Remove
the J1 connection to terminal 3 and connect it to terminal 2. Remove the small back wire
connected to the right side of terminal 3, and connect it to right side of terminal 2. Remove the
large white wire connected to the left side of terminal 6 and connect it to the left side of terminal
5. Make sure all screws are tightened.
You are now ready to replace the amplifier's top cover. The hot air exhaust holes should be
located on the top left and the cooling air entry holes should be on the right side. Align the
mounting holes with the corresponding threaded inserts located on the chassis. You may also
need to use an alignment tool such as an awl. You may need to lightly tap the top cover into place
with your hand. The left and right sides of the top cover may need to be pushed inward as you
place the mounting screws into place. Replace the ten 6-32 x 3/8 mounting screws and washers.
Partially tighten each screw. When all ten screws have been inserted, tighten all the screws.
Double check to make sure that the cooling air entry holes are on the right side , and the
hot exhaust air exit holes are located on the top left directly over the tubes.

INTRODUCTION

The QRO Model HF-2500DX Linear Amplifier is a completely self-contained, grounded cathode
grid driven, linear amplifier. It is designed to operate at 1,500 watts peak all modes including SSB,
CW, and continuous or modulated carrier (e.g., RTTY, FM, SSTV). Continuous or modulated
carrier operation for more than 30 minutes at or near maximum rated output power
requires use of auxiliary cooling. The HF-2500DX is designed to be used with any transceiver
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