Icom 751A & Ten Tec Hercules 444

[Ten-Tec Inc.]

>
>Mike,
>
>Is this a new (first time) use of the Hercules? The reason I ask is that I
>recently sold a Hercules II to another ham and he was getting overdrive
>lights and poor power out with his Omni VI; I had been driving it with MY
>Omni VI and had had no such problems. We were stumped until we discovered
>that I had been using the brute-strength Ten Tec power supply or a marine
>deep-cycle battery to power the Herc, and he was using a large mil-surplus
>DC power supply. When he tried a battery, the problem disappeared.
>Evidently, the Hercules is very sensitive to power-supply regulation and
>requires a "stiff" or highly regulated supply with very little "droop".

The original Hercules is like the Hercules II only in name.  The original
Hercules was powered by a stand-alone, 45 volt power supply.  It is not
operable from battery power.  

>The other possibility is a large,leading-edge spike on the output waveform
>of the Icom. It is not unusual for solid-state gear to have a large
>transient on the leading edge of the first or "keydown" signal. For most
>tube amplifiers (excepting some of the Alphas), this presents no immediate
>problem, but transistorized amps can and do react quickly to what they see
>as an overdrive condition. In some cases, this CAN damage the amp if left
>uncorrected.

The protection is added to keep the finals safe.  A leading edge
spike CAN blow the finals in the original Hercules amplifier.  Final
transistors are no longer available for this amp as they were discontinued
a number of years ago by their manufacturer and no suitable replacement 
was offered.  (Which is also why this amp was discontinued from the
Ten-Tec product line).  May want to give a call to Ten-Tec service just
to confirm that this is likely your problem.  

Scott Robbins, W4PA
Ten-Tec 


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