Specifications

Manual Alpha 99 Rev 1.doc

Cover interlocks are intended only as back-up protection against accidents. Never

depend on them! Always disconnect the power cord from the AC mains before

removing the cover! Interlock switches should never be disabled for any reason.

Fuses

Never replace any fuse with one of a different type or greater current rating. Blowing

of one or both primary line fuses indicates that the maximum safe average power

capability of the amplifier has been substantially exceeded or that an equipment failure

has occurred. USE ONLY 20 AMP, 250 VOLT RATED FUSES for 190-220 VAC

service.

Slow-blow fuses F3 and F4, located above the primary line fuses, may prevent damage

to the step-start resistors and HV rectifiers in the event of abnormal turn-on

conditions or HV faults. If the AC interlock is defeated and primary power is applied

while the HV crowbar is closed, the step-start fuses normally will blow.

DAMAGE RESULTING FROM USE OF A FUSE OF INCORRECT SIZE OR

TYPE WILL NOT BE COVERED UNDER WARRANTY AND MAY VOID

THE WARRANTY.

Plate Overcurrent Relay

This relay will quickly turn off the amplifier in the event of grossly excessive plate

current or fault in the high voltage circuitry. The relay will not prevent tube or other

damage due to either short or long term overdrive or improper tuning. It is the

operator’s responsibility to ensure safe tuning, drive, and general operating conditions.

Should the overcurrent relay trip, remove AC power from the amplifier, then

determine and correct the cause of the trip before turning the 99 on again.

Idling Plate Current And Electronic Bias Control (Ebs)

Idling plate current of the ALPHA 99 is approximately 350 to 400 mA during

fullpower transmission. A detector senses RF drive, and reduces plate current to 30-50

mA during pauses in speech and key-up intervals, thus substantially reducing average

power supply loading, heat generation, and wasted energy.

RF & Mistuning Protection

ALPHA/POWER’s exclusive circuit senses the beginning of any RF arc in, for

example, a TUNE or LOAD variable capacitor and automatically switches the 99 to

standby within a few milliseconds. This system has virtually eliminated RF arc damage

in current ALPHA amplifiers. The system similarly detects severe mis-tuning of the 99,

and if drive exceeds about 25 watts switches the amplifier to standby. The 25 watt

input trip threshold permits safe tuneup at low power levels using the TUNE indicator,

without aggravating and unnecessary trip-outs.