20
The Ig2 indicator should have three to four LED's flashing on at peak of modulation. This (combined with a
correct plate tuning), indicates an optimum loading, good efficiency and good linearity. A lower screen current,
due to excessive loading, will reduce the output power, with an equal amount of extra power dissipated by the
tube. A higher screen current, making all four LED's in the Ig2 flashing, will increase the distortion.
11
SWITCHING THE POWER OFF
When you have finished using the amplifier and you want to switch it off, the following procedure is
recommended: Stop transmitting. Put the switch on STBY. Leave the DX-3 running idle for a few minutes, to
cool the tube, then switch the power off.
12
TROUBLESHOOTING - If something goes wrong
12.1
No power
When you switch on a DX-2, it takes about 3 - 5 seconds for the lights on the front panel display to come on.
This is due to the "soft start" circuit. If nothing happens after turning the power on, switch off at the front panel,
then check the following:
make sure the power point has power
make sure the power plug is fully pushed in into the power outlet.
If it is still not working, unplug the power cord from the mains, then remove the fuses from the fuse holders on
the rear, panel of DX-3 and check them with an ohmmeter. If a fuse is blown, replace it with a fuse of the same
type and try again. If the fuse blows again, or if the fuses were not blown in the first place, contact your
supplier.
12.2
Fan not working
As soon as you switch the power on, you should notice two things about your DX-3: the display should indicate
about 3400V of plate voltage
and you should be able to hear the fan running. The amplifier is not supposed to be
powered without the fan, even in idling mode. If the fan does not operate when you power up, or if it stops
while using the amplifier, switch the mains power off immediately and contact your supplier.
12.3
If the FAULT light turns on
The FAULT (red) light turns on in two situations:
Over-current in the plate circuit
This could happen due to a flash-over in the tube, or as a result of a momentary high plate current during tuning.
This completely disables the amplifier for about 2 minutes. The same timer is activated as when the amplifier is
switched on, causing the READY light to turn off. If the front panel is put on STBY, the FAULT will turn off,
but the READY will be also off. When the READY comes on again, the FAULT will disappear (if the amplifier
was left in OPR), and the DX-3 is ready to operate again, after putting the switch on OPR.
Over-temperature cut-off.
See below.
12.4
Over-temperature cut-off
The operation of the amplifier is disabled, but the timer is not activated. When the tube cools down, the FAULT
light turns off, READY turns on and the operation can resume. DX-3 has a very efficient air cooling system.
When the ventilation is not restricted, in normal ambient conditions, when properly tuned, a DX-3 can operate at
