Alpha 9500 HF Linear Amplifier Operating Manual Alpha Radio Products
Diagnosing Faults Product Release 1
DOCNUMBER 9500
Document Issue 1, Revision 7
Page 9–4 June 2009
99
To ease initial installation of the amplifier, it is shipped with automatic tap
selection enabled. This is appropriate for most situations, but it is possible
that a particular situation may fake the voltage estimation circuitry out,
and cause the amplifier to select an inappropriate tap. This can result in
off-nominal conditions for the plate and heater voltages.
The reasons for this fault are several. It is likely that either the AC supply
is floating (has a poorly defined ground reference) or the waveform is
significantly distorted (by spikes or other irregularities).
It is possible to operate the amplifier with some of these less-than-perfect
p
ower sources by enabling the force-tap-selection option. For information
on how to force tap selection, contact ALPHA technical support.
Resolution 1. Measure the line voltage using an accurate voltmeter. Compare this
value with the reported value in the amplifier telemetry stream. This
is most easily done by running the AlphaRemote/9500 software. The
line voltage is reported in the rectangle around the meter selection
buttons. If necessary, this can be done with the amplifier plugged in
but in the OFF condition.
2. If the reported and measured values differ by mor
e than a few volts,
investigate the cause. Possible reasons are:
•
Poor AC voltage waveform (check with an oscilloscope)
•
Poor ground (check from chassis to Line A and Line B)
If neither of these cases seem to exist, it is possible that the
measurement circuitry on the mains board has drifted. If this is the
case, contact ALPHA technical support.
3. Assuming the value is being reported correctly, compare this value to
th
e values in the following table. There are 5 possible primary tap
selections, with values as indicated.
Tap number Min voltage Max voltage
1 89.9 109.9
2 110.0 135.0
3 189.9 209.9
4 210.0 229.9
5 230.0 265.0
The amplifier selects the tap appropriat
e to the range reported as
being measured. If the measured value does not fall into one of the 5
ranges, the amplifier does not turn on unless you activate manual tap
selection.
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