User's Manual

ALPHA 9500 Interim OPERATING MANUAL

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voltages (less than 100 volts). If you do, be aware that the higher current at the lower voltage

will signiﬁcantly warm the power cord for the ampliﬁer. The cord (as well as fuse holders and

some internal connectors) are operating near their maximum ratings due to the current demand

at lower voltages. Be sure that the AC cord is not coiled too tightly or placed where normal air

ﬂow is restricted because the cord could overheat. If other equipment is drawing current from

the same circuit as the Alpha 9500, then the considerations in section 4.2.3 should be taken into

account.

High Voltage and Tube Life

At the high end (sometimes encountered when using poorly regulated generators) the plate

voltage and tube heater voltage may be too high. If voltages above 250 volts are applied for any

length of time, the lifetime of the tubes may be reduced. If this is your situation, the ﬁrst line of

defense is to contact your utility company and ask if they can reduce your line voltage. If this is

not possible, you may want to consider placing your own step-down transformer in line between

the AC outlet and the ampliﬁer. If this is necessary, a transformer with at least 4-kVA rating is

required, due to the nature of the current waveform in the primary. Another choice for voltage

control, a ferro-resonant voltage regulator, is an expensive solution, but is a good way to stabilize

primary voltage.

Note: If you intend to operate the ampliﬁer on any of the 90 - 130V settings, the two lower 2

amp fuses on the rear panel will have to be changed to 5 amp to allow for the increased in-rush

current.

4.4 Complete the Transformer Installation

4.4.1 RF Grounding

A ground stud with wing nut is provided on the rear of the chassis. Connection should be made

from this stud to a good RF earth ground, such as a copper water pipe or driven rod, via heavy

copper braid or strap.

CAUTION:

When using any high power ampliﬁer, failure to connect ALL station

equipment to a good common ground may allow RF feedback to leak into the

transceiver and cause severe signal distortion.

4.4.2 Replacing the Ampliﬁer Cover