DOCNUMBER 9500
Document Issue 1, Revision 7
June 2009 Page 9–3
Alpha Radio Products Alpha 9500 HF Linear Amplifier Operating Manual
Product Release 1 Diagnosing Faults
As noted previously, this fault (and several others) are inhibited (disabled)
if the drive power into the amplifier from the exciter is less than 20 W.
The amplifier is generally safe at this drive power level, and it provides a
window for you to exercise the various controls to either get the amplifier
tuned to within the nominal gain range or determine the underlying cause
of the problem.
Resolution 1. . Ensure that the load is good under low power. Put the amplifier in
bypass mode, and note the standing wave ratio (swr) reported by the
exciter. If it is very high, check the antenna/load.
2. If you have recently switched to a new exciter, ensure that it is not
putting out excessive power. It has been found that even new
transceivers from reputable suppliers develop problems that cause
them to put out power much higher than expected, either transiently
or continuously. High input power can cause the amplifier to saturate,
and the reported gain to drop. Drive powers above 100 W can damage
the amplifier and cause this fault. Within-range drive powers at the
wrong frequency can also cause this fault.
3. Ensure that the plate voltage (Vp on the digital meter) is within limits
(3.0 to 3.8 kV).
•
At the low end of this range, the amplifier struggles to meet the
gain specification. It is possible that the mains board has set an
inappropriate tap on the primary of the transformer. This can
happen for several reasons, but a procedure has been
implemented that enables you to override the automatic tap
selection feature and force the amplifier to set any desired
primary taps. For information on how to force tap selection,
contact ALPHA technical support.
•
At the high end of this range, it is also possible that an incorrect
tap has been set, although this normally causes a different fault
code.
Fault code 2
Description Tap not found.
Explanation The mains board has measured a line voltage that does not correspond to
an acceptable primary tap setting.
The mains board has a set of relays that can select an appropriate
combination of primary windings for the power transformer. The tap can
be selected either automatically based on the mains board estimate of line
voltage, or by force when you tell the amplifier which tap to use.
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